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Carbapenem resistance among bacteria, especially Klebsiella pneumoniae and Acinetobacter baumannii, constitutes a dreadful threat to public health all over the world that requires developing new medications urgently. Carbapenem resistance emerges as a serious problem as this class is used as a last-line option to clear the multidrug-resistant bacteria. Arthrospira maxima (Spirulina) is a well-known cyanobacterium used as a food supplement as it is rich in protein, essential minerals and vitamins and previous studies showed it may have some antimicrobial activity against different organisms. Biosynthesized (green) zinc oxide nanoparticles have been investigated by several researchers as antibacterials because of their safety in health. In this article, previous studies were analyzed to get to a conclusion about their activity as antibacterials., Competing Interests: Declarations Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Introduction: Diabetes mellitus is a chronic metabolic disorder characterized by persistent hyperglycemia due to impaired insulin production or utilization, leading to severe health complications. Diabetic foot ulcers (DFUs) represent a major complication, often exacerbated by polymicrobial infections involving Staphylococcus aureus and Acinetobacter baumannii. These pathogens, notorious for their resistance to antibiotics, complicate treatment efforts, especially due to biofilm formation, which enhances bacterial survival and resistance. This study explores the synergistic effects of combining gentamicin, imipenem, and fucoidan, a sulfated polysaccharide with antimicrobial properties, against both planktonic and biofilm forms of S. aureus and A. baumannii., Methods: Isolates of S. aureus and A. baumannii were collected from DFUs and genetically confirmed. Methicillin resistance in S. aureus was identified through disk diffusion and PCR. Biofilm formation, including dual-species biofilms, was analyzed using the microtiter plate method. The antimicrobial efficacy of gentamicin, imipenem, and fucoidan was assessed by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC). Synergistic interactions were evaluated using the fractional inhibitory concentration index (FICi) and fractional bactericidal concentration index (FBCi). The expression of biofilm-associated genes (icaA in S. aureus and bap in A. baumannii) was analyzed, and the cytotoxicity of fucoidan was assessed., Results: The study revealed that 77.4% of S. aureus and all A. baumannii isolates showed multidrug resistance. Among 837 tested conditions for dual-species biofilm formation, 72 resulted in strong biofilm formation and 67 in moderate biofilm formation. The geometric mean MIC values for gentamicin were 12.2 µg/mL for S. aureus, 22.62 µg/mL for A. baumannii, and 5.87 µg/mL for their co-culture; for imipenem, they were 19.84, 9.18, and 3.70 µg/mL, respectively, and for fucoidan, 48.50, 31.20, and 19.65 µg/mL, respectively. The MBC values for gentamicin were 119.42, 128, and 11.75 µg/mL; for imipenem, they were 48.50, 14.92, and 8 µg/mL; and for fucoidan, they were 88.37, 62.62, and 42.48 µg/mL. The MBIC values were 55.71, 119.42, and 18.66 µg/mL for gentamicin; 68.59, 48.50, and 25.39 µg/mL for imipenem; and 153.89, 101.49, and 53.53 µg/mL for fucoidan. The MBEC values were 315.17, 362.03, and 59.25 µg/mL for gentamicin; 207.93, 157.58, and 74.65 µg/mL for imipenem; and 353.55, 189.46, and 99.19 µg/mL for fucoidan. When cultured in planktonic form, the geometric mean FICi and FBCi values indicated additive effects, while co-culture showed FICi values of ≤ 0.5, suggesting a synergistic interaction. Treatment with gentamicin and fucoidan led to significant downregulation of the icaA and bap genes in both single-species and dual-species biofilms of S. aureus and A. baumannii. The reductions in gene expression were more pronounced in dual-species biofilms compared to single-species biofilms. Additionally, treatment with imipenem and fucoidan also resulted in significant downregulation of these genes in both biofilm types. Cytotoxicity assessments indicated that higher concentrations of fucoidan were toxic, yet no harmful effects were noted at the optimal synergistic concentrations used with antibiotics., Conclusion: In our investigation, we found that combining gentamicin, imipenem, and fucoidan had a synergistic effect on dual-species biofilms of S. aureus and A. baumannii, suggesting potential benefits for treating such infections effectively. This underscores the importance of understanding microbial interactions, antibiotic susceptibility, and biofilm formation in DFUs., Competing Interests: Declarations Ethics approval and consent to participate The Ethics Review Board of the Hamadan University of Medical Sciences, Hamadan, Iran approved the present study (Ethical approval code: IR.UMSHA.REC.1401.809). Ethical Review Board approved informed consent taken from all the participants, and all experiments were performed in accordance with relevant guidelines and regulations. We reported our findings according to the STROBE guidelines. Consent for publication Not applicable. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Background: Acinetobacter baumannii (AB) is a notable cause of hospital-acquired infections, with carbapenem-resistant Acinetobacter baumannii (CRAB) classified as a high-priority critical pathogen. Bacteriophage therapy is emerging as a promising alternative to combat drug-resistant bacterial infections. In this study, a lytic phage, HZY2308, was isolated from hospital sewage, and the biological properties, biosafety and anti-biofilm properties of phage HZY2308 were characterized and identified. Moreover, the antibacterial effect of phage HZY2308 in combination with antibiotics was investigated, and the apparent characteristics of phage-resistant strain AB48-R were demonstrated, which provided data support for further studies to elucidate the mechanism of generating phage resistance., Methods: Phage HZY2308 was isolated by double agar plate method using clinical strain AB48 as the host bacterium. The morphology of phage HZY2308 was identified by transmission electron microscopy (TEM), and biological characteristics of phage HZY2308 were identified by host range, the efficiency of plating (EOP), sensitivity to temperature, pH, and chloroform, one-step growth curve, the optimal multiplicity of infection (MOI), and detection of endotoxin and cytotoxicity. Besides, the complete genome map of HZY2308 was constructed using CGview, and the phylogenetic tree of HZY2308 was constructed with MEGA. Additionally, the full genomic sequence of phage HZY2308 and the selected phage were compared using Easyfig. Checkerboard test of phage HZY2308 in combination with tigecycline (TGC) was performed to investigate their synergistic effect and bactericidal kinetics. The effect of HZY2308 on biofilm was investigated by semi-quantitative staining of biofilm with crystal violet, determination of bacterial activity in biofilm by 2,3-Bis (2-methoxy-4-nitro-5-sulfophenyl) -2 H-tetrazolium-5-carboxanilide (XTT) assay and observation of biofilm structure by fluorescence microscopy. Finally, Phage-resistant bacteria AB48-R were characterized by colony-forming capacity, morphology, growth curves, adsorption efficiency, and antibiotic susceptibility assays., Results: A lytic phage, HZY2308, was isolated from hospital sewage, which exhibited advantageous traits such as a brief incubation period, large burst size, and robust stability. Safety assessments conducted at both genetic and cellular levels also have yielded positive outcomes. Besides, phage HZY2308 effectively inhibited AB biofilm formation and disrupted established biofilm structures. Furthermore, a synergistic antibacterial effect was noted when phage HZY2308 was combined with tigecycline. Interestingly, the phage-resistant strain, AB48-R was screened through natural selection. Compared to the wild strain AB48, the adsorption efficiency of the phage to AB48-R diminished. However, AB48-R's sensitivity to antibiotics such as cefepime, gentamicin, amikacin, and tobramycin increased, indicating an evolutionary trade-off., Conclusions: Phage HZY2308 shows strong antimicrobial potential, especially in combination with tigecycline, and the phage-resistant strain exhibits increased antibiotic sensitivity., (© 2024. The Author(s).)

This study reports the activity of cefiderocol against Enterobacterales, Pseudomonas aeruginosa , and Acinetobacter spp. isolates collected from the United States and Europe, including Israel and Turkey, from 2020 to 2021. Among Enterobacterales, 2.8% were carbapenem nonsusceptible (CNSE); cefiderocol inhibited 96.6%/85.1% [Clinical Laboratory Standards Institute (CLSI)/European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints] of these isolates. Imipenem-relebactam, meropenem-vaborbactam, and ceftazidime-avibactam displayed susceptibilities lower than cefiderocol against CNSE isolates (67.4-84.6% susceptible, CLSI). Cefiderocol was the only agent active against CNSE isolates carrying metallo-β-lactamase (MBL) carbapenemase or multiple carbapenemase genes (84.6%-92.3% susceptible, CLSI). Approximately 18% of carbapenem-susceptible Escherichia coli , Klebsiella pneumoniae , and Proteus mirabilis carried extended-spectrum-β-lactamases and/or plasmid-borne AmpC-encoding genes; cefiderocol inhibited 99.8%-100.0% (CLSI) of these genotypic groups. Multi-drug resistance (MDR) phenotypes were observed in 16.9% and 52.5% of P. aeruginosa and A. baumannii-calcoaceticus isolates, respectively. Carbapenemase genes were rare (4.9%) among cephalosporin and/or carbapenem nonsusceptible P. aeruginosa , compared to 87.6% carriage in A. baumannii-calcoaceticus , respectively. Against the MDR and carbapenemase-carrying P. aeruginosa and A. baumannii-calcoaceticus subsets, cefiderocol was active against 98.6%/98.7% and 97.1%/97.4% (CLSI), respectively. Only 69 isolates (0.3%) across all species groups were identified as cefiderocol nonsusceptible per CLSI criteria (>4 mg/L). Cefiderocol was the most active agent in vitro against Enterobacterales, P. aeruginosa, and Acinetobacter spp., with uniform activity against all phenotypic- and genotypic-resistant subsets. Coupled with the low incidence of nonsusceptibility observed across species groups, these results demonstrate cefiderocol as an important option for treating infections caused by pathogens with diverse mechanisms of resistance in US and European hospitals.IMPORTANCEThe worldwide spread of multi-drug-resistant Pseudomonas aeruginosa and carbapenem-resistant Enterobacterales and Acinetobacter spp. poses a serious challenge in healthcare settings as infections caused by these organisms are commonly refractory to many frontline therapeutic agents. Multiple global health organizations highlighted these pathogens as critical priorities for new antibiotic development, thus necessitating continued surveillance of the activities of currently available antimicrobial agents and circulating mechanisms of resistance. To meet this need, this study phenotypically and genotypically characterized priority Gram-negative pathogens collected from patients in US and European hospitals to examine the activity of cefiderocol and other currently available treatment options, including carbapenems and β-lactam-β-lactamase inhibitor combinations. The results presented here provide a detailed perspective to healthcare practitioners of cefiderocol's broad applicability, manifested in high activity and low nonsusceptibility rates, across phenotypic and genotypic organism groups relative to other agents and further support its use against the most intransigent infections., Competing Interests: The authors declare a conflict of interest (see Acknowledgments).

Since March 2022, an increase was observed in multidrug-resistant microorganisms (MDRO), associated with the hospital transfer of Ukrainian patients. The goal was to collect phenotypic susceptibility data and assess clinical implications. Carbapenemase-producing Enterobacterales (CPE, n = 96), Pseudomonas aeruginosa (CPPA, n = 20), and carbapenem-resistant Acinetobacter baumannii-calcoaceticus (CRAB, n = 6) from Ukrainian patients were obtained from March to December 2022 from the Dutch MDRO surveillance. Antimicrobial susceptibility testing was performed using broth microdilution (BMD) when available, fosfomycin agar dilution, disk diffusion (DD) for cefiderocol, and diverse gradient strips. All isolates were sequenced with Illumina next-generation sequencing. For meropenem, aminoglycosides, ceftazidime-avibactam, ceftolozane-tazobactam, and imipenem-relebactam, susceptibility rates were low (0%-30%), due to the high number of bla NDM -positive isolates (79/122; 65%). For cefiderocol, results depended on reading with or without microcolonies, applying EUCAST or CLSI breakpoints, and whether DD or BMD was used; e.g., for Klebsiella pneumoniae , 30%-97% were susceptible. For colistin, 103/111 (93%) non-intrinsically resistant CPE/CPPA/CRAB isolates were susceptible. For most CPE, a low minimal inhibitory concentration (MIC) of <0.5 mg/L was measured for tigecycline and ceftazidime-avibactam-aztreonam. For CPPA, cefiderocol tested susceptible in 65%-100% of isolates. For CRAB, ampicillin-sulbactam MICs were ≥128 mg/L; for sulbactam-durlobactam, 1-2 mg/L. Admission in a Ukrainian hospital in the last year was a risk factor for MDRO, and majority were screening isolates (79%). There is extensive phenotypic resistance to last-resort antibiotics in MDRO from Ukrainian patients. Interpretation of cefiderocol susceptibility results depends on several variables. When treating patients recently admitted in Ukraine, suspected for Gram-negative bacterial infection, this should be taken into consideration., Importance: Since March 2022, multidrug-resistant microorganisms associated with Ukrainian patients have been detected in national surveillance systems of several European countries. We studied the phenotypic antimicrobial susceptibility to last-resort antibiotics of multidrug-resistant microorganisms from Ukrainian patients in the Netherlands and assessed clinical implications. Our research revealed that there was extensive phenotypic resistance to last-resort antibiotics. Healthcare professionals should be aware of multidrug-resistant microorganisms when treating patients recently admitted in Ukraine, suspected for Gram-negative bacterial infection., Competing Interests: The authors declare no conflict of interest.

This work examined the antibacterial and antibiofilm properties of alginate/collagen nanoparticles containing limonene. The multi-drug resistant (MDR) strains were screened, and the morphological features of the produced nanoparticles were determined utilizing SEM, DLS, and FTIR. Additionally, the encapsulation effectiveness, stability, and drug release were assessed. The levels of OmpA and Bap biofilm genes were assessed using qRT-PCR. At the same time, the antibacterial and cytotoxic activities of the nanoparticles were evaluated using well diffusion and MTT techniques, respectively. LAC nanoparticles measuring 300 ± 9.6 nm in size, 83.64 ± 0.19% encapsulation efficiency, and 60-day stability at 4 °C were synthesized. The biological investigation demonstrated that LAC nanoparticles had potent antibacterial capabilities. This was shown by their ability to significantly decrease the transcription of OmpA and Bap biofilm genes at a statistically significant level of p ≤ 0.05. The nanoparticles exhibited reduced antibiotic resistance compared to free limonene and alginate/collagen. Compared to limonene, LAC nanoparticles exhibited negligible cytotoxicity against HEK-293 at doses ranging from 1.56 to 100 µg/mL (p ≤ 0.01). The findings underscore the potential of LAC nanoparticles as a breakthrough in the fight against highly resistant pathogens. The potent antibacterial effects of LAC nanoparticles versus Acinetobacter baumannii (A. baumannii) MDR strains, considered highly resistant pathogens of significant concern, could inspire new strategies in antibacterial research., (© 2024. The Author(s).)

The frequent occurrence of Acinetobacter baumannii in hospital settings and the elevated rate of antimicrobial resistance in this pathogen represent a serious clinical and public health threat worldwide, and particularly in Lebanon where outbreak surveillance and control are still insufficient. Whole-genome sequencing (WGS) is a fast and reliable tool to study outbreaks at the molecular level and obtain actionable knowledge, leading to better control measures. A total of 59 A. baumannii isolates were collected from intensive care unit (ICU) patients (57 isolates) and from the hospital environment (2 isolates) between August 2022 and May 2023, antimicrobial susceptibility testing (AST) was performed and gDNA was subjected to WGS. Analysis was performed to reveal the sequence types (ST), the relatedness to strains that caused other outbreaks and the arsenal of resistance genes harboured by these bacteria. Of 59 isolates, 85% were categorised as extensively drug-resistant (XDR), 13.6% as multidrug-resistant (MDR) and 1.7% as pan-drug-resistant. All isolates belonged to international clone (IC)2, of which the majority were of ST2 (91.5%). The isolates clustered well with those of a previous outbreak in the same hospital. In addition, isolates from hospitals in Lebanon clustered well together and some clustered with those originating from other countries. The observed genetic relatedness between the current isolates and those from the previous outbreaks underscores the importance of strict surveillance to limit the threat of outbreaks. Moreover, the clustering of isolates from Lebanon with others from distant countries proves the necessity to further investigate the international spread of drug-resistant pathogens and the implementation of control strategies., Competing Interests: Declarations Funding: None. Competing Interests: None declared. Ethical Approval: Ethical approval was obtained from the Institutional Review Board (IRB) at AUB under the number BIO-2023-0185. Sequence Information: The WGS data of the isolates analysed in this work have been deposited in the National Center for Biotechnology Information (NCBCI) database under BioProject number PRJNA613441, with the following accession numbers: Biosamples SAMN38010223 to SAMN38010281., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Acinetobacter baumannii (A. baumannii) has become a significant nosocomial pathogen globally over the past decade due to the increasing prevalence of antibiotic-resistant isolates. The formation of the mucoid phenotype is a crucial adaptive defense response to external pressure, but the clinical, phenotypic and genotypic characteristics and their relationship with sequence types (ST) and K locus (KL) types remain unclear., Methods: In this study, we screened a total of 736 A. baumannii isolates, from which we identified and characterized 13 mucoid isolates. The study explored the clinical characteristics of patients with mucoid isolates, investigated the mucoid phenotype, performed capsule observation, quantified capsule production, and assessed antimicrobial susceptibility. Subsequently, whole-genome sequencing (WGS) was used to analyze the sequence types (ST), loci for capsular polysaccharide (KL), antibiotic resistance genes, virulence genes, and core-genome single-nucleotide polymorphisms (SNPs). Additionally, the virulence of all mucoid strains was evaluated through serum resistance assay, biofilm-forming assay, and Galleria mellonella survival assay., Results: All mucoid A. baumannii isolates were found to be encapsulated and extremely drug-resistant. Among patients infected with these isolates, 92.3 % had pulmonary infections, and the 30-day mortality rate was 61.5 %. The analysis revealed that not all strains are highly virulent. Whole-genome sequencing (WGS) identified the sequence types as ST136, ST208, ST381, ST195, and ST281, and the capsular types as KL77, KL7, KL33, KL2, and KL3. The ST208 and KL7 isolates exhibited higher virulence and greater biofilm formation, with KL7 isolates also showing higher capsule production. Despite these differences, no significant variations in virulence genes were observed among the mucoid isolates, except for biofilm-associated and quorum-sensing genes. The highly virulent ST208/KL7 strains (AB276, AB313, and AB552) lacked biofilm-associated genes (csuA/BABCDE), indicating these genes do not directly cause differences in biofilm formation., Conclusion: The mucoid A. baumannii isolates were extensively drug-resistant, and infections caused by these isolates could lead to higher mortality. However, not all strains had high virulence, with variations likely related to specific sequence types (ST) and K locus (KL) types., Competing Interests: Declaration of competing interest The authors report no conflicts of interest in this work., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Antibiotics have been a vital component in the fight against microbial diseases for over 75 years, saving countless lives. However, the global rise of multi-drug-resistance (MDR) bacterial infections is pushing us closer to a post-antibiotic era where common infections may once again become lethal. To combat MDR Acinetobacter baumannii, we investigated chiral phthalimides and used molecular docking to identify potential targets. Outer membrane protein A (OmpA) is crucial for A. baumannii resistant to antibiotics, making it a pathogen of great concern due to its high mortality rate and limited treatment options. In this study, we evaluated three distinct compounds against the OmpA protein: FIA (2-(1,3-dioxoindolin-2yl)-3-phenylpropanoic acid), FIC (2-(1,3-dioxoindolin-2yl)-4-(methylthio) butanoic acid), and FII (3-(1,3-dioxoindolin-2yl)-3-phenylpropanoic acid). Molecular docking results showed that these three compounds exhibited strong interactions with the OmpA protein. Molecular dynamics (MD) simulation analysis further confirmed the stability and binding efficacy of these compounds with OmpA. Their antimicrobial activities were assessed using the agar well diffusion method, revealing that FIA had an optimal zone of inhibition of 24 mm. Additionally, the minimum inhibitory concentrations (MIC) of these compounds were determined, demonstrating their bactericidal properties against A. baumannii, with MICs of 11 μg/μL for FIA, 46 μg/μL for FIC, and 375 μg/μL for FII. In vitro cytotoxicity data indicated that none of the three compounds were hemolytic when exposed to human red blood cells. This finding is particularly significant as it highlights the superior efficacy of FIA against A. baumannii compared to the other compounds. With thorough pharmacokinetic validations, these chiral phthalimides are promising alternative therapeutic options for treating infections caused by A. baumannii, offering new hope in the face of rising antibiotic resistance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

We compared clinical outcomes of patients who received monotherapy and combination therapy for treatment of MDR A. baumannii VAP. 170 patients were included. Vasopressor use and mortality rate were higher for combination therapy (69.3% versus 28.6%, p=0.024; 67.5% versus 14.3%, p=0.007; respectively). Majority received polymyxin B-based combination therapy, with higher mortality than those without polymyxin B (80.2% versus 19.8%, p=0.043). After adjusting for vasopressor use, monotherapy, dual combination, and triple combination therapy were not associated with mortality (aHR 0.24, 95% CI 0.03 to 1.79, p=0.169; aHR 1.26, 95% CI 0.79 to 2.00, p=0.367; aHR 0.93, 95% CI 0.57 to 1.49, p=0.744; respectively). There was no difference in adverse effects and length of stay between the two groups. Mortality from MDR A. baumannii VAP was high and not associated with monotherapy or combination therapy after adjustment for vasopressor use. Antibiotic regimens other than those containing polymyxin are urgently needed for the treatment of these infections., Competing Interests: Declaration of competing interest None., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Microecological equilibrium is essential for human health. Previous research has demonstrated that Streptococcus strain A, the main bacterial group in the respiratory tract, can suppress harmful microbes and protect the body. In this study, Streptococcus strain D19 T was isolated from the oral and pharyngeal cavities of healthy children. Its antibacterial mechanism against Acinetobacter baumannii was examined, as well as its potential to prevent inflammatory damage to cells. We evaluated the effect of the fermentation conditions of D19 T on inhibition of Acinetobacter baumannii growth; Isolation and purification of antibacterial active components of strain D19 T and molecular mechanism of inhibition of Acinetobacter baumannii; Molecular mechanism of D19 T antibacterial protein reversing cellular inflammatory injury induced by Acinetobacter baumannii., Results: The supernatant of fermentation broth of Streptococcus D19 T was the active component against Acinetobacter baumannii, but the bacteria had no antibacterial activity. The supernatant of D19 T fermentation broth was precipitated by (NH 4 ) 2 SO 4 solution, and the protein was the active antibacterial component. After gel filtration chromatography and anion gel filtration chromatography, the molecular weight of antibacterial protein was 53kD. D19 T antibacterial protein can improve cell membrane permeability, limit extracellular soluble protein release, inhibit Acinetobacter baumannii biofilm formation, and prevent Acinetobacter baumannii adhesion. Acinetobacter baumannii induces inflammatory damage to respiratory cells via ferroptosis, and the D19 T antibacterial protein can counteract this damage, protecting the respiratory tract., Conclusion: Streptococcus strain D19 T , as a potential probiotic, inhibits the growth of Acinetobacter baumannii and the inflammatory damage of respiratory cells, playing a protective role in human respiratory health., (© 2024. The Author(s).)

Background: The extensively drug-resistant (XDR) strains of Acinetobacter baumannii have become a major cause of nosocomial infections, increasing morbidity and mortality worldwide. Many different treatments, including phage therapy, are attractive ways to overcome the challenges of antibiotic resistance., Methods: This study investigates the biofilm formation ability of 30 XDR A. baumannii isolates and the efficacy of a cocktail of four tempetate bacteriophages (SA1, Eve, Ftm, and Gln) and different antibiotics (ampicillin/sulbactam, meropenem, and colistin) in inhibiting and degrading the biofilms of these strains., Results: The majority (83.3%) of the strains exhibited strong biofilm formation. The bacteriophage cocktail showed varying degrees of effectiveness against A. baumannii biofilms, with higher concentrations generally leading to more significant inhibition and degradation rates. The antibiotics-bacteriophage cocktail combinations also enhanced the inhibition and degradation of biofilms., Conclusion: The findings suggested that the bacteriophage cocktail is an effective tool in combating A. baumannii biofilms, with its efficacy depending on the concentration. Combining antibiotics with the bacteriophage cocktail improved the inhibition and removal of biofilms, indicating a promising strategy for managing A. baumannii infections. These results contribute to our understanding of biofilm dynamics and the potential of bacteriophage cocktails as a novel therapeutic approach to combat antibiotic-resistant bacteria., (© 2024. The Author(s).)

Inosine 5'-monophosphate dehydrogenase (IMPDH), known as GuaB in bacteria, catalyzes the rate-limiting step in de novo guanine biosynthesis and is conserved from humans to bacteria. We developed a series of potent inhibitors that selectively target GuaB over its human homolog. Here, we show that these GuaB inhibitors are bactericidal, generate phenotypic signatures that are distinct from other antibiotics, and elicit different time-kill kinetics and regulatory responses in two important Gram-negative pathogens: Acinetobacter baumannii and Escherichia coli . Specifically, the GuaB inhibitor G6 rapidly kills A. baumannii but only kills E. coli after 24 h. After exposure to G6, the expression of genes involved in purine biosynthesis and stress responses change in opposite directions while siderophore biosynthesis is downregulated in both species. Our results suggest that different species respond to GuaB inhibition using distinct regulatory programs and possibly explain the different bactericidal kinetics upon GuaB inhibition. The comparison highlights opportunities for developing GuaB inhibitors as novel antibiotics.IMPORTANCE A. baumannii is a priority bacterial pathogen for which development of new antibiotics is urgently needed due to the emergence of multidrug resistance. We recently developed a series of specific inhibitors against GuaB, a bacterial inosine 5'-monophosphate dehydrogenase, and achieved sub-micromolar minimum inhibitory concentrations against A. baumannii . GuaB catalyzes the rate-limiting step of de novo guanine biosynthesis and is highly conserved across bacterial pathogens. This study shows that inhibition of GuaB induced a bacterial morphological profile distinct from that of other classes of antibiotics, highlighting a novel mechanism of action. Moreover, our transcriptomic analysis showed that regulation of de novo purine biosynthesis and stress responses of A. baumannii upon GuaB inhibition differed significantly from that of E. coli ., Competing Interests: The authors declare no conflict of interest.

Guanine nucleotides are required for growth and viability of cells due to their structural role in DNA and RNA, and their regulatory roles in translation, signal transduction, and cell division. The natural antibiotic mycophenolic acid (MPA) targets the rate-limiting step in de novo guanine nucleotide biosynthesis executed by inosine-5´-monophosphate dehydrogenase (IMPDH). MPA is used clinically as an immunosuppressant, but whether in vivo inhibition of bacterial IMPDH (GuaB) is a valid antibacterial strategy is controversial. Here, we describe the discovery of extremely potent small molecule GuaB inhibitors (GuaBi) specific to pathogenic bacteria with a low frequency of on-target spontaneous resistance and bactericidal efficacy in vivo against Acinetobacter baumannii mouse models of infection. The spectrum of GuaBi activity includes multidrug-resistant pathogens that are a critical priority of new antibiotic development. Co-crystal structures of A. baumannii, Staphylococcus aureus , and Escherichia coli GuaB proteins bound to inhibitors show comparable binding modes of GuaBi across species and identifies key binding site residues that are predictive of whole-cell activity across both Gram-positive and Gram-negative clades of Bacteria. The clear in vivo efficacy of these small molecule GuaB inhibitors in a model of A. baumannii infection validates GuaB as an essential antibiotic target., Importance: The emergence of multidrug-resistant bacteria worldwide has renewed interest in discovering antibiotics with novel mechanism of action. For the first time ever, we demonstrate that pharmacological inhibition of de novo guanine biosynthesis is bactericidal in a mouse model of Acinetobacter baumannii infection. Structural analyses of novel inhibitors explain differences in biochemical and whole-cell activity across bacterial clades and underscore why this discovery may have broad translational impact on treatment of the most recalcitrant bacterial infections., Competing Interests: All authors were employed by Genentech, Inc., a member of the Roche Group.

Background: The treatment of carbapenem-resistant Acinetobacter baumannii/calcoaceticus complex (CRAB) presents significant treatment challenges., Methods: We report the case of a 42-year-old woman with CRAB meningitis who experienced persistently positive cerebrospinal fluid (CSF) cultures for 13 days despite treatment with high-dose ampicillin-sulbactam and cefiderocol. On day 13, she was transitioned to sulbactam-durlobactam and meropenem; 4 subsequent CSF cultures remained negative. After 14 days of sulbactam-durlobactam, she was cured of infection. Whole genome sequencing investigations identified putative mechanisms that contributed to the reduced cefiderocol susceptibility observed during cefiderocol therapy. Blood and CSF samples were collected pre-dose and 3-hours post initiation of a sulbactam-durlobactam infusion., Results: The CRAB isolate belonged to sequence type 2. An acquired blaOXA-23 and an intrinsic blaOXA-51-like (ie, blaOXA-66) carbapenemase gene were identified. The paradoxical effect (ie, no growth at lower cefiderocol dilutions but growth at higher dilutions) was observed by broth microdilution after 8 days of cefiderocol exposure but not by disk diffusion. Potential markers of resistance to cefiderocol included mutations in the start codon of piuA and piuC iron transport genes and an A515V substitution in PBP3, the primary target of cefiderocol. Sulbactam and durlobactam were detected in CSF at both timepoints, indicating CSF penetration., Conclusions: This case describes successful treatment of refractory CRAB meningitis with the administration of sulbactam-durlobactam and meropenem and highlights the need to be cognizant of the paradoxical effect that can be observed with broth microdilution testing of CRAB isolates with cefiderocol., Competing Interests: Potential conflicts of interest . S. M. K. and P. J. S. served on an Advisory Board for Entasis/Innoviva Specialty Therapeutics. P. J. S. reports grants from T2 Diagnostics and Accelerate Diagnostics, grants and personal fees from bioMérieux, Inc., and Qiagen Sciences Inc.; and personal fees from BD Diagnostics, Shionogi, Inc., GeneCapture, Day Zero Diagnostics, Next Gen Diagnostics, outside the submitted work. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Acinetobacter baumannii ( A. baumannii ) challenges clinical infection treatment due to its resistance to various antibiotics. Multiple resistance genes in the core genome or mobile elements contribute to multidrug resistance in A. baumannii . Macrolide phosphotransferase gene mphE has been identified in A. baumannii , which is particularly relevant to macrolide antibiotics. Here, we determined the structure of MphE protein in three states: the apo state, the complex state with erythromycin and guanosine triphosphate (GTP), and the complex state with azithromycin and guanosine. Interestingly, GTP and two magnesium ions were observed in the erythromycin-bound MphE complex. This structure captured the active state of MphE, in which the magnesium ions stabilized the active site and assisted the transfer of phosphoryl groups. Based on these structures, we verified that the conserved residues Asp29, Asp194, His199, and Asp213 play an important role in the catalytic phosphorylation of MphE leading to drug resistance. Our work helps to understand the molecular basis of drug resistance and provides reference targets for optimizing macrolide antibiotics.

In the current era of antibiotic resistance, researchers are exploring alternative ways to treat bacterial infections that are resistant to multiple drugs. Acinetobacter baumannii (A. baumannii) is a bacterium that is commonly encountered in clinical settings and is known to be resistant to several drugs. Due to the increase in drug-resistant infections caused by this bacteria, there is an urgent need to investigate alternative treatment options such as phage therapy and combination therapy. Despite the success of phages in some cases, there are some limitations in their clinical application that can be overcome by combining phages with other substrates such as nanoparticles to improve their function. The integration of nanotechnology with phage therapy against A. baumannii promises to overcome antibiotic resistance. By exploiting the targeted delivery and controlled release capabilities of nanoparticles, we can enhance the therapeutic potential of phages while minimizing their limitations. Continued research in this field will undoubtedly pave the way for more effective and precise treatments against A. baumannii infections and provide hope in the fight against antibiotic-resistant bacteria., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Antimicrobial resistance (AMR) in Acinetobacter baumannii is an unmet medical need. Multiple drug-resistant/extremely drug-resistant strains of A. baumannii do not display growth well in in vivo models, and consequently, their response to antibacterial therapy is inconsistent. We addressed this issue by engineering carbapenem resistance motifs into the highly virulent genetic background of A. baumannii AB5075. This strain has a chromosomally encoded oxa-23 that was deleted ( Δoxa-23 ), then plasmids expressing oxa-23 , oxa-24/40 , oxa-58 , imp-1 , vim-2 , and ndm-1 were introduced to create the mutant strains. Each transformant was used as a challenge strain in a neutropenic murine thigh infection model and assessed for the extent of growth and response to meropenem 200 mg/kg subcutaneously every 6 h (q6h). Pharmacodynamic analyses were performed by transforming drug exposure from dose (mg/kg) to the fraction of the dosing interval; free meropenem concentrations were >minimum inhibitory concentration (MIC) ( f T > MIC). AB5075 and the AB5075 Δoxa-23 mutant had a MICs of 32 and 4 mg/L, respectively. The transformants harboring oxacillinases oxa-24/40 and oxa-58 had an MIC of 64 mg/L. The metallo-β-lactamases imp-1 , vim-2 , and ndm-1 had MICs of 128, 64, and 64 mg/L, respectively. All vehicle-treated transformants displayed in vivo growth in the range of 0.75-1.4 log. The response to meropenem was consistent with the varying f T > MIC of the transformants and was readily described by an inhibitory sigmoid E max relationship. Stasis was achieved with a f T > MIC of 0.36. These A. baumannii transformants are invaluable new tools for the assessment of anti- Acinetobacter compounds and provide a new pathway for AMR preparedness., Competing Interests: W.H. holds or has recently held research grants with UKRI, EU (FP7, IMI-1, and IMI-2), Wellcome, F2G, Spero Therapeutics, Antabio, Pfizer, Allecra, Bugworks, Phico Therapeutics, BioVersys, and Global Antimicrobial Research and Development Partnership (GARDP). He is (or has recently been) a consultant for Appili Therapeutics, F2G, Spero Therapeutics, Pfizer, GSK, Phico Therapeutics, Pulmocide, and Mundipharma Research Ltd. He was a member of the Specialist Advisory Committee for GARDP (2020–2023), a member of the British Society for Antimicrobial Chemotherapy Breakpoint Committee (2020–2023), a member of Health Technology Appraisal Prioritisation Committee for hospital care, and the Specialty National Co-lead for Infection for the National Institute of Health Research (2020–2024).

Antimicrobial resistance (AMR) has led to a marked reduction in the effectiveness of many antibiotics, representing a substantial and escalating concern for global health. Particularly alarming is resistance in Gram-negative bacteria due to the scarcity of therapeutic options for treating infections caused by these pathogens. This challenge is further compounded by the rising incidence of resistance to colistin, an antibiotic traditionally considered a last resort for the treatment of multi-drug resistant (MDR) Gram-negative bacterial infections. In this study, we demonstrate that adjuvants restore colistin sensitivity in vivo . We previously reported that the salicylanilide kinase inhibitor IMD-0354, which was originally developed to inhibit the human kinase IKKβ in the NFκB pathway, is a potent colistin adjuvant. Subsequent analog synthesis using an amide isostere approach led to the creation of a series of novel benzimidazole compounds with enhanced colistin adjuvant activity. Herein, we demonstrate that both IMD-0354 and a lead benzimidazole effectively restore colistin susceptibility in mouse models of highly colistin-resistant Klebsiella pneumoniae and Acinetobacter baumannii -induced peritonitis. These novel adjuvants show low toxicity in vivo , significantly reduce bacterial load, and prevent dissemination that could otherwise result in systemic infection., Competing Interests: The authors declare no conflict of interest.

Introduction. Acinetobacter baumannii is a common cause of multidrug-resistant (MDR) nosocomial infections worldwide, including Vietnam. Hypothesis. Analysis of crucial genetic factors may link to epidemiological characteristics and antibiotic resistance of A. baumannii clinical strains in Vietnamese hospitals. Methodology. Fifty-one A . baumannii clinical strains from six different tertiary hospitals in Vietnam were analysed using whole genome sequencing (WGS), between 2017 and 2019. Results. Eleven sequence types (STs) were identified, including four STs reported for the first time in Vietnam based on the PubMLST database and three new STs not previously documented. ST1336, ST1260 and ST575 were found exclusively in Vietnam. These STs were widely distributed in all hospitals in Vietnam, with ST2 and ST571 being the most dominant. Resistant rates to eight antibiotics, belonging to four antibiotic groups, were very high (72.5-94.1 %) with high MIC values, while resistance to colistin was 29.4%. Fifty-one isolates were identified as MDR, with 100% (51/51) isolates carrying antimicrobial-resistant (AMR) genes, and 52 antibiotic-resistant genes were detected among these strains, including β-lactam (22 genes), chloramphenicol (5 genes), lincosamide (2 genes), aminoglycoside (11 genes), rifampicin (1 gene), quinolone (2 genes), sulfonamide and trimethoprim (4 genes) and tetracycline (5 genes) resistance. The most commonly found mobile structures carried partial or complete transposons: ISaba24/ISEc29/ISEc35 contains a series of antibiotic-resistant genes. Conclusion. The WGS results of the 51 strains of A. baumannii provided important information regarding the distribution of STs and associated antibiotic-resistant genes among A. baumannii strains.

Acinetobacter baumannii is a globally distributed opportunistic pathogen in human health settings, including in intensive care units (ICUs). We investigated the contamination of a French small animal ICU with A. baumannii . We discovered repeated animal contamination by A. baumannii , and phylogenetic analysis traced contamination back to a potential foreign animal origin. Genomic analysis combined with antibiotic susceptibility testing revealed heteroresistance to penicillin and aminoglycoside mediated by insertion sequence dynamics and also suggest a potential cross-resistance to human-restricted piperacillin-tazobactam combination. The A. baumannii isolates of the animal ICU belong to the International Clone 2 commonly found in human health settings. Our results suggest a high adaptation of this lineage to healthcare settings and provide questions on the requirements for genetic determinants enabling adaptation to host and abiotic conditions.

In this work, the antibiotic resistance, biofilm formation capability, and clonal relatedness of 50 A. baumannii isolates collected from three hospitals in Ardabil city, Iran, were evaluated. Antibiotic sensitivity and biofilm formation of isolates were determined by disk diffusion and microtiter-plate methods, respectively. Molecular typing of isolates was also performed using repetitive sequence-based PCR (REP-PCR). The majority of isolates were resistant to cephems, aminoglycosides, and carbapenems, with 80 % classified as multi-drug resistant (MDR). While, only isolates collected from blood and tracheal were resistant to colistin. Additionally, 42 isolates (84 %) had biofilm formation capability. According to rep-PCR results, 34 isolates showed similar banding patterns, while 16 isolates had unique banding patterns. Finally, based on the molecular analysis, there was a direct relationship between biofilm formation and the antibiotic resistance of isolates. In other words, MDR isolates had a higher ability to form biofilm., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objectives: Carbapenem-resistant A. baumannii is a common cause of nosocomial meningitis, and it presents a challenge in terms of treatment because of limited therapeutic options. Intravenous tigecycline has been considered a potential salvage therapy against multi-drug-resistant Acinetobacter baumannii . However, its effectiveness is limited by its poor ability to cross the blood-brain barrier. As an alternative treatment option, intrathecal tigecycline has shown promise with its minimal side effects and high concentration in cerebrospinal fluid. Methods: In this report, we present a series of four cases infected with multi-drug-resistant A. baumannii following neurosurgery and treated with intrathecal tigecycline, including antimicrobial therapy. Results: The rate of successful microbiological response was 2 out of 3 cases (66%) in whom microbiological response could be tested anytime during the intrathecal therapy, whereas the 30-day survival rate after treatment completion was ¼ (25%). Conclusion: Although intrathecal tigecycline treatment has shown relative efficacy in achieving microbiological response, its impact on overall survival is still uncertain. Further studies involving larger groups of patients are necessary to evaluate the outcomes of intrathecal tigecycline therapy.

Persister cells constitute a bacterial subpopulation able to survive to high concentrations of antibiotics. This phenotype is temporary and reversible, and thus could be involved in the recurrence of infections and emergence of antibiotic resistance. To better understand how persister cells survive to such high antibiotic concentration, we examined changes in their lipid composition. We thus compared the lipidome of Acinetobacter baumannii ATCC 19606 T persister cells formed under ciprofloxacin treatment with the lipidome of control cells grown without antibiotic. Using matrix assisted laser desorption ionisation-Fourier transform ion cyclotron resonance mass spectrometry, we observed a higher abundance of short chains and secondary chains without hydroxylation for lipid A in persister cells. Using liquid chromatography-tandem mass spectrometry, we found that persister cells produced particular phosphatidylglycerols, as LPAGPE and PAGPE, but also lipids with particular acyl chains containing additional hydroxyl group or uncommon di-unsaturation on C18 and C16 acyl chains. In order to determine the impact of these multiple lipidome modifications on membrane fluidity, fluorescence anisotropy assays were performed. They showed an increase of rigidity for the membrane of persister cells, inducing likely a decrease membrane permeability to protect cells during dormancy. Finally, we highlighted that A. baumannii persister cells also produced particular wax esters, composed of two fatty acids and a fatty diol. These uncommon storage lipids are key metabolites allowing a rapid bacterial regrow when antibiotic pressure disappears. These overall changes in persister lipidome may constitute new therapeutic targets to combat these particular dormant cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: This study continues surveillance of antimicrobial resistance associated with combat injuries in Ukraine., Aim: To compare species composition, antibiotic resistance profiles, and emergence of new resistance genes between 2014-2020 and 2022-2023., Methods: This was a retrospective multi-centre microbiological survey in Ukrainian hospitals. Antibiotic susceptibility, whole-genome sequencing and multi-locus sequence typing were conducted on 154 organisms obtained from 125 casualties between 2022 and 2023., Findings: The data revealed a predominance of Gram-negative bacteria, particularly Acinetobacter baumannii (35.7%), Pseudomonas aeruginosa (14.9%) and Klebsiella pneumoniae (20.7%). High levels of carbapenem resistance were observed among A. baumannii {meropenem 72.2% [39/54, 95% confidence interval (CI) 58.4-83.5]; imipenem 66.7% (36/54, 95% CI 52.5-78.9)}, K. pneumoniae [meropenem 90.6% (29/32, 95% CI 75.0-98.0); imipenem 81.2% (26/32, 95% CI 63.6-92.8)] and P. aeruginosa [meropenem 47.8% (11/23, 95% CI 26.8-69.4); imipenem 60.8% (14/23, 95% CI 38.5-80.3)] strains. A. baumannii sequence type (ST)-78 and ST-400 were prevalent from 2014 to 2020, while five strains of ST-1077 were newly identified in 2022-2023. P. aeruginosa strains showed diversity across 16 STs, with ST-773 increasing in frequency and new STs emerging, but lacking carbapenemase genes. K. pneumoniae exhibited increased genetic diversity over time, with three STs from 2014 to 2020 and six new STs, including bla NDM-1 , bla OXA-48 and bla KPC2 carriers, in 2022-2023., Conclusion: The prevalence of multi-drug-resistant isolates with STs associated with a high risk of global dissemination is increasing., (Copyright © 2024 The Healthcare Infection Society. All rights reserved.)

To assess the antibacterial effectiveness of Lippia macrophylla essential oil (LMEO) against multidrug-resistant Acinetobacter baumannii isolates, both as a standalone treatment and in combination with conventional antibiotics. LMEO demonstrated a significant inhibitory effect on the growth of A. baumannii, with a minimum inhibitory concentration (MIC) below 500 μg/mL. Notably, LMEO was capable of reversing the antibiotic resistance of clinical isolates or reducing their MIC values when used in combination with antibiotics, showing synergistic (FICI≤0.5) or additive effects. The combination of LMEO and imipenem was particularly effective, displaying synergistic interactions for most isolates. Ultrastructural analyses supported these findings, revealing that the combination of LMEO+ceftazidime compromised the membrane integrity of the Acb35 isolate, leading to cytoplasmic leakage and increased formation of Outer Membrane Vesicles (OMVs). Taken together our results point for the use of LMEO alone or in combination as an antibacterial agent against A. baumannii. These findings offer promising avenues for utilizing LMEO as a novel antibacterial strategy against drug-resistant infections in healthcare settings, underscoring the potential of essential oils in enhancing antibiotic efficacy., (© 2024 Wiley-VHCA AG, Zurich, Switzerland.)

Emerging antimicrobial resistance has highlighted the need to design more effective antibiotics to treat deadly bacterial infections. Acinetobacter baumannii' s outer membrane protein A (OmpA) is a critical virulence component involved in biofilm formation, immunomodulation, and antibiotic resistance, which characterizes it as a potential therapeutic target. The present study aimed to screen the natural product database (>1,00,000) to identify the potential inhibitor against OmpA. Molecular docking studies revealed that 10 compounds had good docking scores (≤ -7 kcal/mol) compared to the reported inhibitor epiestriol (-3.079). Further, these 10 compounds were subjected to ADME analysis and MMGBSA analysis. Based on MMGBSA results, we selected 5 compounds [NP-1 (MolPort-039-337-117), NP-5(MolPort-019-932-973), NP-6 (MolPort-005-948-336), NP-8(MolPort-042-673-978) and NP-9(MolPort-042-673-766)] with high binding affinity. Molecular dynamics simulation found that NP-5, NP-8, and NP-9 were stable after analysing their RMSD, RMSF, the radius of gyration, and hydrogen interactions of complexes. Our study revealed that NP-5, NP-8, and NP-9 bind perfectly with OmpA and can act as its potential inhibitors. The results of this study imply that the identified inhibitors have the potential for further investigation.Communicated by Ramaswamy H. Sarma.

We evaluated the efficacy of the adoptive transfer of memory B, CD4+, and CD8+ T lymphocytes compared with sulbactam and tigecycline in an experimental murine pneumonia model by two multidrug-resistant Acinetobacter baumannii strains, colistin-susceptible AbCS01 and colistin-resistant AbCR17. Pharmacodynamically optimized antimicrobial dosages were administered for 72 h, and intravenous administration of 2 × 10 6 of each of the memory cells in a single dose 30 min post-infection. Bacterial lung and blood counts and mortality rates were analyzed. Results showed that a single dose of memory B or CD4+ T cells was as effective as sulbactam in terms of bacterial clearance from the lungs and blood compared with the untreated mice or the tigecycline-treated mice inoculated with the AbCS01 strain. In the pneumonia model by AbCR17, a single dose of memory B or CD4+ T cells also reduced the bacterial load in the lungs compared with both antibiotic groups and was more efficacious than tigecycline in terms of blood clearance. Regarding survival, the adoptive transfer of memory B or CD4+ T cells was as effective as three days of sulbactam treatment for both strains. These data suggest that adoptive memory cell transfer could be a new effective treatment of multidrug-resistant A. baumannii infections.

This study addresses the distribution and antimicrobial resistance of Acinetobacter baumannii (A. baumannii) in a medical facility in Haikou City, aiming to provide essential insights for enhancing in-hospital treatment and prevention strategies. We conducted a retrospective analysis of 513 A. baumannii isolates collected from a tertiary care hospital in Haikou between January 2018 and December 2020, focusing on their antimicrobial resistance patterns. Random Amplified Polymorphic DNA (RAPD) analysis was performed on 48 randomly selected A. baumannii strains. Using Gel-pro4.0 and NTSYSspc2.10 software, we constructed dendrograms to assess the genetic diversity of these strains. Our results indicate that males between 60 and 70 years old are particularly vulnerable to A. baumannii infections, which are most frequently detected in sputum samples, with a detection rate exceeding 70%. Alarmingly, over 50% of the isolates were identified as multi-drug resistant. The RAPD-PCR fingerprinting cluster analysis demonstrated substantial genetic diversity among the strains. Using primer OPA-02 at a 45% similarity coefficient, the strains were categorized into four groups (A-D), with group A being predominant (39 strains). high-prevalence areas like the Neurosurgery and Intensive Care Medicine Wards require enhanced surveillance and targeted interventions to manage Group C infections effectively. Additionally, the varied presence of other groups necessitates customized strategies to address the specific risks in each ward. Similarly, primer 270 at a 52% similarity coefficient classified the strains into five groups (E-I), with group E being most common (36 strains). The study highlights a concerning prevalence of antimicrobial resistance, particularly multi-drug resistance, among A. baumannii strains in the Haikou hospital. The significant genetic diversity, especially within groups A and E, underscores the need for tailored hospital treatment protocols and prevention measures. These findings contribute to the growing body of research on antimicrobial resistance, emphasizing the urgent need for effective management strategies in healthcare settings., (© 2024. The Author(s).)

Introduction: There are multiple ongoing outbreaks of carbapenem resistant Acinetobacter baumannii (CR Ab ) infection in Fiji's hospitals. CR Ab is able to colonize and persist on various hospital surfaces for extended periods. We conducted a study to understand the extent of hospital environmental contamination and phylogenetic links with clinical isolates., Methods: Swabs were collected from high-touch surfaces at Colonial War Memorial Hospital (CWMH) September 2021 and December 2022; Lautoka Hospital (LTKH) August 2022; and Labasa Hospital (LBSH) November 2022. All bacterial isolates were identified, and antimicrobial susceptibility testing (AST) performed; isolates resistant to carbapenems and producing a carbapenemase underwent whole genome sequencing. Comparison was made to clinical isolates obtained from CWMH in 2016-2017 and 2019-2021 and from LTKH and LBSH from 2020-2021., Results: From the 180 environmental samples collected, ten (5.6%) CR Ab were isolated; no other carbapenem-resistant gram-negative organisms were isolated. Seven (70%) of the CR Ab were isolated from CWMH and three (30%) from LTKH; no CR Ab were isolated from LBSH. Of the seven CWMH CR Ab , two were sequence type 2 (ST2), three ST25, and two ST499. All LTKH isolates were ST499. The two environmental CR Ab ST2 isolates were closely genetically linked to isolates obtained from patients in CWMH, LTKH, and LBSH 2020-2021. Similarly, the three environmental CR Ab ST25 isolates were closely genetically linked to isolates obtained from patients admitted to CWMH in 2019-2021 and LBSH in 2020. The environmental CR Ab ST499 isolates represented two distinct clones, with clone 1 comprising two genetically identical isolates from CWMH and clone 2 the three isolates from LTKH. Although no genetic linkages were observed when comparing environmental ST499 isolates to those from CWMH patients in 2020-2021, both clone 1 isolates were genetically identical to an isolate obtained from a patient admitted during the sampling period., Conclusion: Our study highlights the contamination of high-touch surfaces within Fiji hospitals with CR Ab , suggesting that these may serve as important sources for CR Ab . Phylogenetic linkages to CR Ab isolated from patients since 2019 underscores the persistence of this resistant pathogen in hospital settings and the ongoing risk for hospital-acquired infections., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Baleivanualala, Matanitobua, Samisoni, Soqo, Smita, Mailulu, Nabose, Lata, Shayam, Sharma, Wilson, Crump and Ussher.)

The quorum sensing (QS) system mediated by the abaI gene in Acinetobacter baumannii is crucial for various physiological and pathogenic processes. In this study, we constructed a stable markerless abaI knockout mutant (ΔabaI) strain using a pEXKm5-based allele replacement method to investigate the impact of abaI on A. baumannii. Proteomic analysis revealed significant alterations in protein expression between the wild type (WT) and ΔabaI mutant strains, particularly in proteins associated with membrane structure, antibiotic resistance, and virulence. Notably, the downregulation of key outer membrane proteins such as SurA, OmpA, OmpW, and BamA suggests potential vulnerabilities in outer membrane integrity, which correlate with structural abnormalities in the ΔabaI mutant strain, including irregular cell shapes and compromised membrane integrity, observed by scanning and transmission electron microscopy. Furthermore, diminished expression of regulatory proteins such as OmpR and GacA-GacS highlights the broader regulatory networks affected by abaI deletion. Functional assays revealed impaired biofilm formation and surface-associated motility in the mutant strain, indicative of altered colonization capabilities. Interestingly, the mutant showed a complex antibiotic susceptibility profile. While it demonstrated increased susceptibility to membrane-targeting antibiotics, its response to beta-lactams was more nuanced. Despite increased expression of metallo-beta-lactamase (MBL) superfamily proteins and DcaP-like protein, the mutant unexpectedly showed lower MICs for carbapenems (imipenem and meropenem) compared to the wild-type strain. This suggests that abaI deletion affects antibiotic susceptibility through multiple, potentially competing mechanisms. Further investigation is needed to fully elucidate the interplay between quorum sensing, antibiotic resistance genes, and overall antibiotic susceptibility in A. baumannii. Our findings underscore the multifaceted role of the abaI gene in modulating various cellular processes and highlight its significance in A. baumannii physiology, pathogenesis, and antibiotic resistance. Targeting the abaI QS system may offer novel therapeutic strategies for this clinically significant pathogen., (© 2024. The Author(s).)

Background: The continuous emergence and spread of polymyxin-resistant Acinetobacter baumannii pose a significant global health challenge, necessitating the development of novel therapeutic strategies. Aloe, with its long-standing history of medicinal use, has recently been the subject of substantial research for its efficacy against pathogenic infections., Methods: This study investigates the potential application of anthraquinone components in aloe against polymyxin-resistant A. baumannii by liquid chromatography-mass spectrometry, in vitro activity assessment, and construction of animal infection models., Results: The findings demonstrate that aloe emodin, emodin, rhein, and their mixtures in equal mass ratios (EAR) exhibit strain-specific antibacterial activities against polymyxin-resistant A. baumannii . Co-administration of EAR with EDTA synergistically and universally enhanced the antibacterial activity and bactericidal efficacy of polymyxins against polymyxin-resistant A. baumannii , while also reducing the frequency of polymyxin-resistant mutations in polymyxinssensitive A. baumannii . Following toxicity assessment on human hepatic and renal cell lines, the combination therapy was applied to skin wounds in mice infected with polymyxin-resistant A. baumannii . Compared to monotherapy, the combination therapy significantly accelerated wound healing and reduced bacterial burden., Conclusions: The combination of EAR and EDTA with polymyxins offers a novel therapeutic approach for managing skin infections caused by polymyxinresistant A. baumannii ., Competing Interests: Authors MC and SW were employed by the company Shandong Aobo Biotechnology Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhao, Zhang, Liang, Xie, Pan, Cao, Wang, Wu, Wang, Wang and Hu.)

Purpose: Acinetobacter baumannii is emerging as a pathogen that is a focus of global concern due to the frequent occurrence of the strains those are extensively resistant to antibiotics. This study was aimed to analyze the clinical and microbiological characteristics of a cohort of patients with A. baumannii bloodstream infections (BSIs) in western China., Methods: A retrospective study of the patients at West China Hospital of Sichuan University with A. baumannii BSIs between Jan, 2018 and May, 2023 was conducted. Antimicrobial susceptibility of A. baumannii isolates was tested by microdilution broth method. Whole-genome sequencing and genetic analysis were also performed for these isolates., Results: Among the 117 patients included, longer intensive care unit stay, higher mortality, and more frequent invasive procedures and use of more than 3 classes of antibiotics were observed among the carbapenem-resistant A. baumannii (CRAB)-infected group (n = 76), compared to the carbapenem-susceptible A. baumannii (CSAB)-infected group (n = 41, all P ≤ 0.001). Twenty-four sequence types (STs) were determined for the 117 isolates, and 98.7% (75/76) of CRAB were identified as ST2. Compared to non-ST2 isolates, ST2 isolates exhibited higher antibiotic resistance, and carried more resistance and virulence genes (P < 0.05). In addition, 80 (68.4%) isolates were CRISPR-positive, showed higher antibiotic susceptibility, and harbored less resistance and virulence genes, in comparison to CRISPR-negative ones (P < 0.05). Phylogenetic clustering based on coregenome SNPs indicated a sporadic occurrence of clonal transmission., Conclusion: Our findings demonstrate a high frequency of ST2 among A. baumannii causing BSIs, and high antibiotic susceptibility of non-ST2 and CRISPR-positive isolates. It is necessary to strengthen the surveillance of this pathogen., (© 2024. The Author(s).)

Objectives: Acinetobacter baumannii is classified by the centre for Disease Control and Prevention (CDC) as an "urgent threat" due to its ability to acquire and develop resistance to multiple classes of antibiotics. As a result, it is one of the most concerning pathogens in healthcare settings, with increasing incidence of infections due to carbapenem-resistant Acinetobacter baumannii (CRAB) associated with high morbidity and mortality rates. Therefore, there are ongoing efforts to find novel treatment options, one of which is cefiderocol. We aim to review available evidence on cefiderocol use for severe nosocomial pneumonia due to carbapenem-resistant Acinetobacter baumannii., Methods: A comprehensive review was conducted from 2017 to 2023, covering articles from databases such as Pubmed, Scopus, and Embase, along with conference proceedings from ECCMID 2023. The primary focus was on severe nosocomial pneumonia due A. baumannii and cefiderocol., Discussion: Cefiderocol, targeting periplasmic space Penicillin-Binding Proteins (PBPs) via siderophore transport pathways, exhibits promise against multi-drug resistant Gram-negative bacilli. Its effectiveness in treating CRAB pneumonia remains debated. The CREDIBLE trial reported higher mortality with cefiderocol compared to the best available treatment, while other cohort studies showed contrasting outcomes. Patient variations and pharmacokinetic factors may underlie these discrepancies. The recommended cefiderocol dosage regimen may fall short of desired pharmacokinetic targets, especially in critically ill patients and lung infections. Pulmonary factors hindering cefiderocol's entry into bacteria through iron transporters are overlooked in clinical breakpoints. Optimized dosing or combination regimens may enhance infection site exposure and outcomes., Conclusions: Further research is needed to determine the optimal cefiderocol dosage and administration (mono vs. dual therapy, continuous vs. intermittent infusion), in severe Acinetobacter baumannii nosocomial pneumonia., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

To evaluate the in vitro activity of ampicillin-sulbactam and cefoperazone-sulbactam against A. baumannii using the broth disk elution testing, a total of 150 A. baumannii isolates were collected from across China between January 2019 and January 2021, including 51 carbapenem-susceptible and 99 carbapenem-resistant isolates. Broth disk elution (BDE) and the broth microdilution (BMD) method were performed for all strains. The concentration range of the BDE was 10/10 µg/mL, 20/20 µg/mL, and 30/30 µg/mL for ampicillin-sulbactam, and 37.5/15 µg/mL, 75/30 µg/mL, 112.5/45 µg/mL, and 150/60 µg/mL for cefoperazone-sulbactam, respectively. Compared with BMD, the BDE results of ampicillin-sulbactam and cefoperazone-sulbactam showed a categorical agreement of 83.3% (125/150) and 95.3% (143/150), with minor errors of 16.7% (25/150) and 4.7% (7/150), respectively. No major error or very major errors were detected. The sensitivity differences by BDE of carbapenem-resistant A. baumannii (CRAb) to different concentrations of ampicillin-sulbactam showed statistically significant (p < 0.017), while those to cefoperazone-sulbactam at 37.5/15 µg/mL, 75/30 µg/mL, and 112.5/45 µg/mL were significant (p < 0.008). However, no significant difference in sensitivity was observed between 112.5/45 µg/mL and 150/60 µg/mL (p > 0.008). In conclusion, the BDE is a reliable and convenient method to detect the in vitro activity of cefoperazone-sulbactam against A. baumannii, and the results could serve as a clinical reference value when deciding whether or not to use high-dose sulbactam for the treatment of A. baumannii infections., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

One of the significant issues in treating bacterial infections is the increasing prevalence of extensively drug-resistant (XDR) strains of Acinetobacter baumannii. In the face of limited or no viable treatment options for extensively drug-resistant (XDR) bacteria, there is a renewed interest in utilizing bacteriophages as a treatment option. Three Acinetobacter phages (vB&#95;AbaS&#95;Ftm, vB&#95;AbaS&#95;Eva, and vB&#95;AbaS&#95;Gln) were identified from hospital sewage and analyzed for their morphology, host ranges, and their genome sequences were determined and annotated. These phages and vB&#95;AbaS&#95;SA1 were combined to form a phage cocktail. The antibacterial effects of this cocktail and its combinations with selected antimicrobial agents were evaluated against the XDR A. baumannii strains. The phages exhibited siphovirus morphology. Out of a total of 30 XDR A. baumannii isolates, 33% were sensitive to vB&#95;AbaS&#95;Ftm, 30% to vB&#95;AbaS&#95;Gln, and 16.66% to vB&#95;AbaS&#95;Eva. When these phages were combined with antibiotics, they demonstrated a synergistic effect. The genome sizes of vB&#95;AbaS&#95;Ftm, vB&#95;AbaS&#95;Eva, and vB&#95;AbaS&#95;Gln were 48487, 50174, and 50043 base pairs (bp), respectively, and showed high similarity. Phage cocktail, when combined with antibiotics, showed synergistic effects on extensively drug-resistant (XDR) strains of A. baumannii. However, the need for further study to fully understand the mechanisms of action and potential limitations of using these phages is highlighted., Competing Interests: Declarations Conflict of interests The authors declare no competing interests. Ethics approval The present study was approved by the Ethics Committee of Kerman University of Medical Sciences (Ethics code: IR.KMU.REC.1400.526.)., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

This study refers to the intricate world of Acinetobacter baumannii , a resilient pathogenic bacterium notorious for its propensity at antibiotic resistance in nosocomial infections. Expanding upon previous findings that emphasised the bifunctional enzyme PaaY, revealing unexpected γ-carbonic anhydrase (CA) activity, our research focuses on a different class of CA identified within the A. baumannii genome, the β-CA, designated as 𝛽-AbauCA (also indicated as CanB), which plays a crucial role in the resistance mechanism mediated by AmpC beta-lactamase. Here, we cloned, expressed, and purified the recombinant 𝛽-AbauCA, unveiling its distinctive kinetic properties and inhibition profile with inorganic anions (classical CA inhibitors). The exploration of 𝛽-AbauCA not only enhances our understanding of the CA repertoire of A. baumannii but also establishes a foundation for targeted therapeutic interventions against this resilient pathogen, promising advancements in combating its adaptability and antibiotic resistance.

Objectives: To summarize the clinical characteristics, outcomes and identify risk factors of Acinetobacter baumannii (AB) meningitis in children., Methods: This was a single-center, retrospective study. Children hospitalized between January 2016 and December 2021 who were diagnosed with AB meningitis were included. The clinical characteristics and outcomes were reviewed. Risk factors were determined using univariate analyses (chi-square and Mann-Whitney U tests)., Results: Seventeen patients were included; 15 cases were secondary to neurosurgery, and two were neonates with primary bacterial meningitis. Common symptoms included fever, convulsions and nervous system abnormalities. Cerebrospinal fluid (CSF) tests typically showed increased white blood cell counts dominated by neutrophils, reduced glucose levels and elevated protein levels. Ten patients were successfully treated (successful treatment [ST] group); seven had failed treatment (failed treatment [FT] group). Univariate analyses revealed that mechanical ventilation, routine white cell counts in the peripheral blood, procalcitonin, protein in the CSF, septic shock and carbapenem-resistant AB (CRAB) differed significantly between the groups., Conclusion: AB meningitis in children has a high mortality rate. FT was associated with mechanical ventilation, septic shock, CRAB, lower peripheral leukocyte counts, higher protein levels in the CSF and procalcitonin. Larger studies are needed to identify independent risk factors for adverse outcomes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wang, Ye, Fu, Wu, Xu, Ye, Han, Wang and Yu.)

Development of novel antibacterial agents is imperative due to the increasing threat of antibiotic-resistant pathogens. This study aimed to develop the enhanced antibacterial activity and in-vivo efficacy of a novel truncated endolysin, CHAP SAP26 -161, derived from the endolysin LysSAP26, against multidrug-resistant bacteria. CHAP SAP26 -161 exhibited higher protein purification efficiency in E. coli and antibacterial activity than LysSAP26. Moreover, CHAP SAP26 -161 showed the higher lytic activity against A. baumannii with minimal bactericidal concentrations (MBCs) of 5-10 μg/ml, followed by Staphylococcus aureus with MBCs of 10-25 μg/ml. Interestingly, CHAP SAP26 -161 could lyse anaerobic bacteria, such as Clostridioides difficile , with MBCs of 25-50 μg/ml. At pH 4-8 and temperatures of 4°C-45°C, CHAP SAP26 -161 maintained antibacterial activity without remarkable difference. The lytic activity of CHAP SAP26 -161 was increased with Zn 2+ . In vivo tests demonstrated the therapeutic effects of CHAP SAP26 -161 in murine systemic A. baumannii infection model. In conclusion, CHAP SAP26 -161, a truncated endolysin that retains only the CHAP domain from LysSAP26, demonstrated enhanced protein purification efficiency and antibacterial activity compared to LysSAP26. It further displayed broad-spectrum antibacterial effects against S. aureus , A. baumannii , and C. difficile . Our in vitro and in-vivo results of CHAP SAP26 -161 highlights its promise as an innovative therapeutic option against those bacteria with multiple antibiotic resistance.

The potential antimicrobial activity and low propensity to induce the development of bacterial resistance have rendered antimicrobial peptides (AMPs) as novel and ideal candidate therapeutic agents for the treatment of infections caused by drug-resistant pathogenic bacteria. The targeting of bacterial membranes by AMPs has been typically considered their sole mode of action; however, increasing evidence supports the existence of multiple and complementary functions of AMPs that result in bacterial death. An in-depth characterization of their mechanism of action could facilitate further research and development of AMPs with higher potency. The current study employs biophysics and proteomics approaches to unveil the mechanisms underlying the antibacterial activity of A11, a potential candidate AMP, against Acinetobacter baumannii , a leading cause of hospital-acquired infections (HAIs) and consequently, a serious global threat. A11 peptide was found to induce membrane depolarization to a high extent, as revealed by flow cytometry and electron microscopy analyses. The prompt intracellular penetration of A11 peptide, observed using confocal microscopy, was found to occur concomitantly with a very low degree of membrane lysis, suggesting that its mode of action predominantly involves a nonlytic killing mechanism. Quantitative proteomics analysis employed for obtaining insights into the mechanisms underlying the antimicrobial activity of A11 peptide revealed that it disrupted energy metabolism, interfered with protein homeostasis, and inhibited fatty acid synthesis that is essential for cell membrane integrity; all these impacted the cellular functions of A. baumannii . A11 treatment also impacted signal transduction associated with the regulation of biofilm formation, hindered the stress response, and influenced DNA repair processes; these are all crucial survival mechanisms of A. baumannii . Additionally, robust antibacterial activity was exhibited by A11 peptide against multidrug-resistant (MDR) and extensively drug-resistant (XDR) clinical isolates of A. baumannii ; moreover, A11 peptide exhibited synergy with levofloxacin and minocycline as well as low propensity for inducing resistance. Taken together, the findings emphasize the therapeutic potential of A11 peptide as an antibacterial agent against drug-resistant A. baumannii and underscore the need for further investigation.

Acinetobacter baumannii is one of the most important pathogens worldwide. The intrinsic and acquired resistance of A. baumannii , coupled with the slow pace of novel antimicrobial drug development, poses an unprecedented and enormous challenge to clinical anti-infective therapy of A. baumannii . Recent studies in the field of pathogenicity, antibiotic resistance, and biofilms of A. baumannii have focused on the model strains, including ATCC 17978, ATCC 19606, and AB5075. However, these model strains represent only a limited portion of the heterogeneity in A. baumannii . Furthermore, variants of these model strains have emerged that show significant diversity not only at the genotypic level but also reflected in differences at the phenotypic levels of capsule, virulence, pathogenicity, and antibiotic resistance. Research on A. baumannii , a key pathogen, would benefit from a standardized approach, which characterizes heterogeneous strains in order to facilitate rapid diagnosis, discovery of new therapeutic targets, and efficacy assessment. Our study provides and describes a standardized, genomically and phenotypically heterogeneous panel of 45 different A. baumannii strains for the research community. In addition, we performed comparative analyses of several phenotypes of this panel. We found that the sequence type 2 (ST2) group showed significantly higher rates of resistance, lower fitness cost for adaptation, and yet less biofilm formation. The Macrocolony type E (MTE, flat center and wavy edge phenotype reported in the literature) group showed a less clear correlation of resistance rates and growth rate, but was observed to produce more biofilms. Our study sheds light on the complex interplay of resistance fitness and biofilm formation within distinct strains, offering insights crucial for combating A. baumannii infection., Importance: Acinetobacter baumannii is globally notorious, and in an effort to combat the spread of such pathogens, several emerging candidate therapies have already surfaced. However, the strains used to test these therapies vary across studies (the sources and numbers of test strains are varied and often very large, with little heterogeneity). The variation complicates the studies. Furthermore, the limited standardized resources of A. baumannii strains have greatly restricted the research on the physiology, pathogenicity, and antibiotic resistance. Therefore, it is crucial for the research community to acquire a standardized and heterogeneous panel of A. baumannii . Our study meticulously selected 45 diverse A. baumannii strains from a total of 2,197 clinical isolates collected from 64 different hospitals across 27 provinces in China, providing a scientific reference for the research community. This assistance will significantly facilitate scientific exchange in academic research., Competing Interests: The authors declare no conflict of interest.

Acinetobacter baumannii is an ESKAPE pathogen and threatens human health by generating infections with high fatality rates. A. baumannii leads to a spectrum of infections such as skin and wound infections, endocarditis, meningitis pneumonia, septicaemia and urinary tract infections. Recently, strains of A. baumannii have emerged as multidrug-resistant (MDR), meaning they are resistant to at least three different classes of antibiotics. MDR development is primarily intensified by widespread antibiotic misuse and inadequate stewardship. The World Health Organization (WHO) declared A. baumannii a precarious MDR species. A. baumannii maintains the MDR phenotype via a diverse array of antimicrobial metabolite-hydrolysing enzymes, efflux of antibiotics, impermeability and antibiotic target modification, thereby complicating treatment. Hence, a deeper understanding of the resistance mechanisms employed by MDR A. baumannii can give possible approaches to treat antimicrobial resistance. Resistance-nodulation-cell division (RND) efflux pumps have been identified as the key contributors to MDR determinants, owing to their capacity to force a broad spectrum of chemical substances out of the bacterial cell. Though synthetic inhibitors have been reported previously, their efficacy and safety are of debate. As resistance-modifying agents, phytochemicals are ideal choices. These natural compounds could eliminate the bacteria or interact with pathogenicity events and reduce the bacteria's ability to evolve resistance. This review aims to highlight the mechanism behind the multidrug resistance in A. baumannii and elucidate the utility of natural compounds as efflux pump inhibitors to deal with the infections caused by A. baumannii .

Antibiotic resistance has become a global threat as it is continuously growing due to the evolution of β-lactamases diminishing the activity of classic β-lactam (BL) antibiotics. Recent antibiotic discovery and development efforts have led to the availability of β-lactamase inhibitors (BLIs) with activity against extended-spectrum β-lactamases as well as Klebsiella pneumoniae carbapenemase (KPC)-producing carbapenem-resistant organisms (CRO). Nevertheless, there is still a lack of drugs that target metallo-β-lactamases (MBL), which hydrolyze carbapenems efficiently, and oxacillinases (OXA) often present in carbapenem-resistant Acinetobacter baumannii. This review aims to provide a snapshot of microbiology, pharmacology, and clinical data for currently available BL/BLI treatment options as well as agents in late stage development for CRO harboring various β-lactamases including MBL and OXA-enzymes., (© 2024 Pharmacotherapy Publications, Inc.)

Phage therapy offers a promising approach to combat the growing threat of antimicrobial resistance. Yet, key questions remain regarding dosage, administration routes, combination therapy, and the causes of therapeutic failure. In this study, we focused on a novel lytic phage, ФAb4B, which specifically targeted the Acinetobacter baumannii strains with KL160 capsular polysaccharide, including the pan-drug resistant A. baumannii YQ4. ФAb4B exhibited the ability to effectively inhibit biofilm formation and eradicate mature biofilms independently of dosage. Additionally, it demonstrated a wide spectrum of antibiotic-phage synergy and did not show any cytotoxic or haemolytic effects. Continuous phage injections, both intraperitoneally and intravenously over 7 d, showed no acute toxicity in vivo. Importantly, phage therapy significantly improved neutrophil counts, outperforming ciprofloxacin. However, excessive phage injections suppressed neutrophil levels. The combinatorial treatment of phage-ciprofloxacin rescued 91% of the mice, a superior outcome compared to phage alone (67%). The efficacy of the combinatorial treatment was independent of phage dosage. Notably, prophylactic administration of the combinatorial regimen provided no protection, but even when combined with a delayed therapeutic regimen, it saved all the mice. Bacterial resistance to the phage was not a contributing factor to treatment failure. Our preclinical study systematically describes the lytic phage's effectiveness in both in vitro and in vivo settings, filling in crucial details about phage treatment against bacteriemia caused by A. baumannii, which will provide a robust foundation for the future of phage therapy., (Copyright © 2024 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.)

Acinetobacter baumannii, which is predominantly responsible for hospital-acquired infections, presents a tremendous clinical challenge due to its increasing antibiotic resistance to colistin (COL), a last-line antibiotic. As a result, the combination of antimicrobial and non-antimicrobial agents is emerging as a more popular treatment approach against infections caused by COL-resistant A. baumannii. This study administered COL and verapamil (VER), that is an antihypertensive and antiarrhythmic agent. We found that the susceptibility of A. baumannii to COL was restored both in vitro and in vivo. Scanning electron microscope and Crystal violet staining showed inhibition of the VER/COL combination on bacterial biofilm formation. Cytotoxicity assay and haemolysis test were used to confirm in vitro safety evaluation. Further experiments using propidium iodide staining revealed that the VER/COL combination improved the therapeutic efficacy of COL by modifying the permeability of bacterial membranes. As demonstrated by reactive oxygen species experiments, the drug combination caused the accumulation of bacterial reactive oxygen species and their eventual death. Additionally, VER/COL treatment significantly reduced the efflux of Rhodamine 123 (Rh123). For the first time, this study identifies the anti-hypertensive drug VER as a COL potentiator against A. baumannii, providing a potential treatment approach against A. baumannii infections and improving patient outcomes., (Copyright © 2024 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.)

Rhamnolipids, a major category of glycolipid biosurfactant, have recently gained enormous attention in medical field because of their relevance as effective antibacterial agents against a wide variety of pathogenic bacteria. Our previous studies have shown that rhamnolipids from an environmental isolate of Pseudomonas aeruginosa UKMP14T possess antibacterial, anti-adhesive and anti-biofilm activity against multidrug-resistant ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter sp.) pathogens. However, the mechanism of their antibacterial action remains unclear. Thus, this study aimed to elucidate the mechanism of the antibacterial action of P. aeruginosa UKMP14T rhamnolipids by studying the changes in cells of one of the ESKAPE pathogens, Acinetobacter baumannii, which is the most difficult strain to kill. Results revealed that rhamnolipid treatment rendered A. baumannii cells more hydrophobic as evaluated through contact angle measurements. It also induced the release of cellular proteins measuring 510 μg/mL at a rhamnolipid concentration of 1000 μg/mL. In addition, rhamnolipids were found to be bactericidal in their action as they could permeate the inner membranes, leading to a leak-out of nucleotides. More than 50 % of the cells were found to be killed upon 1000 μg/mL rhamnolipid treatment as observed through fluorescence microscopy. Other cellular changes such as irregular shape and size, membrane perturbations, clumping, shrinkage and physical damage were clearly visible in SEM, FESEM and laser micrographs. Furthermore, rhamnolipid treatment inhibited the levels of acyl-homoserine lactones (AHLs) in A. baumannii, which are vital for their biofilm formation and virulence. The obtained results indicate that P. aeruginosa UKMP14T rhamnolipids target outer and inner bacterial membranes through permeation, including physical damage to the cells, leading to cell leakage. Furthermore, AHL inhibition appears to be the mechanism behind their anti-biofilm action. All these observations can be correlated to rhamnolipids' antibacterial effect against A. baumannii., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

This case series describes the clinical course of 10 patients who received eravacycline antimicrobial therapy for a variety of different Acinetobacter baumannii infection types at a community care hospital., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Introduction: Acinetobacter baumannii (AB) is rising as a human pathogen of critical priority worldwide as it is the leading cause of opportunistic infections in healthcare settings and carbapenem-resistant AB is listed as a "super bacterium" or "priority pathogen for drug resistance" by the World Health Organization., Methods: Clinical isolates of A. baumannii were collected and tested for antimicrobial susceptibility. Among them, carbapenem-resistant and carbapenem-sensitive A. baumannii were subjected to prokaryotic transcriptome sequencing. The change of sRNA and mRNA expression was analyzed by bioinformatics and validated by quantitative reverse transcription-PCR., Results: A total of 687 clinical isolates were collected, of which 336 strains of A. baumannii were resistant to carbapenem. Five hundred and six differentially expressed genes and nineteen differentially expressed sRNA candidates were discovered through transcriptomic profile analysis between carbapenem-resistant isolates and carbapenem-sensitive isolates. Possible binding sites were predicted through software for sRNA21 and adeK , sRNA27 and pgaC , sRNA29 and adeB , sRNA36 and katG , indicating a possible targeting relationship. A negative correlation was shown between sRNA21 and adeK (r = -0.581, P = 0.007), sRNA27 and pgaC (r = -0.612, P = 0.004), sRNA29 and adeB (r = -0.516, P = 0.020)., Discussion: This study preliminarily screened differentially expressed mRNA and sRNA in carbapenem-resistant A. baumannii , and explored possible targeting relationships, which will help further reveal the resistance mechanism and provide a theoretical basis for the development of drugs targeting sRNA for the prevention and treatment of carbapenem-resistant A. baumannii infection., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wei, Xin, Zhang, Liao, Rong, Zhong, Zhao, Ma and He.)

Introduction: Mediastinitis remains one of the most serious complications of cardiac surgery. The reported incidence is 1-4%, while the related mortality varies from 10-47%., Case Presentation: A patient with triple vessel disease (TVD) was hospitalized at our clinic for coronary artery bypass graft (CABG) surgery. The preoperative examination results were normal. We performed standard CABG under extracorporeal circulation. The patient had a favorable postoperative course. On the fifth postoperative day, the wound showed seropurulent drainage. The treatment of the patient's wound continued with open dressing, negative wound pressure device, debridement, minimal muscle plasticity, and total bilateral muscle pectoral flap plasticity. The infecting microorganism was identified as multidrug-resistant Acinetobacter baumani, and systemic antibiotic therapy was initiated. The patient had "per secundum closure" of the wound after all these efforts. The wound healed completely 2 months after discharge, and the patient was in good health., Conclusions: Mediastinitis is associated with high mortality and high financial and human costs. The occurrence of this high-risk complication can be prevented through constant vigilance at every step from admission to discharge., Competing Interests: No Conflict of Interest is declared, (Copyright (c) 2024 Selman Dumani, Edmond Puca, Ermal Likaj, Stavri Llazo, Edlira Rruci, Vera Beca, Ali Refatllari, Arben Baboci.)

We report the emergence of cefiderocol resistance in a bla OXA-72 carbapenem-resistant Acinetobacter baumannii isolate from a sacral decubitus ulcer. Cefiderocol was initially used; however, a newly approved sulbactam-durlobactam therapy with source control and flap coverage was successful in treating the infection. Laboratory investigation revealed cefiderocol resistance mediated by IS Aba36 insertion into the siderophore receptor pirA ., Competing Interests: The authors declare no conflict of interest.