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Background and purpose: Acinetobacter species have emerged as major causes of nosocomial infections. Acinetobacter baumannii, the most common clinical subspecies, can cause a wide range of nosocomial infections, including pneumonia, bloodstream infections, and wound infections. These infections are often associated with high mortality rates due to the increasing prevalence of drug resistance among these bacteria. The production of β-lactamases is a significant mechanism of resistance to β-lactams. The transcription of these β-lactamase genes is enhanced by various insertion sequences (ISs) located nearby. The insertion sequences most commonly associated with carbapenem genes in multidrug-resistant Acinetobacter baumannii isolates are ISAba1, ISAba2, ISAba3, ISAba4, and IS18. This study aimed to evaluate the drug resistance patterns and molecular detection of ISAba1 and ISAba2 insertion sequences in A. baumannii isolates recovered from hospitalized patients in Sari teaching hospitals. Materials and methods: This study was conducted over six months, from March 2022 to August 2022, in Sari teaching hospitals. Ninety A. baumannii isolates were collected from various clinical specimens of hospitalized patients. To confirm the species of A. baumannii, various phenotypic tests such as TSI, oxidase, MR/VP, OF, urea, citrate, and SIM were employed. The antibiotic susceptibility pattern of the isolates was evaluated using the disk diffusion method according to the CLSI 2021 guidelines. The minimum inhibitory concentration (MIC) of colistin was determined using the micro broth method. To evaluate the presence of ISAba1 and ISAba2 genes, the Polymerase Chain Reaction (PCR) method was performed using specific primers. Data were analyzed using SPSS version 22 software. The chi-square test was used to determine significant differences, with a P-value less than or equal to 0.05 considered statistically significant. Results: The results of this study showed that A. baumannii isolates had a high level of resistance to several antibiotics, including ciprofloxacin, imipenem, doripenem, cefepime, ceftazidime, piperacillin/tazobactam, and piperacillin, with all isolates (100%) being resistant to these antibiotics. However, the highest susceptibility was observed for the antibiotic colistin (98.8%). Additionally, the frequencies of ISAba1 and ISAba2 genes among the isolates were 95.5% and 81.1%, respectively, indicating a high prevalence of these genetic elements among the study isolates. Conclusion: The results of this study indicate a high susceptibility of isolates to the antibiotic colistin, but due to the risk of resistance development and nephrotoxicity, it should be used with caution. The findings suggest that the presence of insertion elements such as ISAba1 and ISAba2 plays a significant role in increasing the expression of drug-resistance genes and their transfer in Acinetobacter baumannii. This can help explain the high prevalence of drug resistance in these bacteria and highlights the importance of detecting and controlling these factors to reduce nosocomial infections. Therefore, identifying and controlling these factors can be an effective step in improving prevention and treatment methods for infections caused by A. baumannii.

Abstract Background and objectives Of the genes conferring resistance to carbapenems in Acinetobacter baumannii, the bla OXA−23 gene is the most widely found across the world. The gene carrying bla OXA−23 transposons in A. baumannii isolates of global clones GC1 and GC2 is found worldwide. Here, we examined whether transposons play a role in the dissemination of the bla OXA−23 in globally distributed clones, GC1 and GC2 A. baumannii isolates from Iraq. Materials and methods The 119 non-repetitive A. baumannii isolates including 94 recovered from clinical specimens and 25 isolates from hospital environment between September 2021 and April 2022 from different medical centers located at various regions in Baghdad, Iraq. The global clones (GC) and the genes encoding carbapenem resistance, including bla OXA−23, bla OXA−24, and bla OXA−58 were identified using multiplex PCR assays. Antibiotic susceptibility testing was performed by the Kirby-Bauer disk diffusion susceptibility method. The transposons carrying bla OXA−23 were examined using PCR mapping. In cases when carbapenem susceptible A. baumannii isolates were found, they were subjected to E test, full length sequencing of bla OXA−Ab (bla OXA−51−like) and Institut Pasteur multi-locus sequence typing scheme. Results All but two isolates (92 clinical and 25 environmental) were identified carbapenem-resistant A. baumannii (CRAB). Of 117 CRAB isolates, 20 belong to GC1, 19 contained bla OXA−23; of them, 17 isolates harbored the bla OXA−23 located on Tn2006. Among the 46 CRAB belonging to GC2, 39 contained bla OXA−23; of them, 34 carried the bla OXA−23 located on Tn2006. The remaining GC1 and GC2 isolates, one GC1 as well as one GC2 isolate, were susceptible to imipenem, doripenem, and meropenem and considered carbapenem-susceptible A. baumannii (CSAB). Full-length sequencing of the bla OXA−Ab and MLST for the two CSAB isolates belonging to GC1 and GC2 confirmed that the GC1 isolate belongs to ST 623 and contained an allele that encodes an bla OXA−69 variant of the bla OXA−Ab while the GC2 belong to ST2 and carried an bla OXA−66 variant. Conclusion This study provides evidence for the dissemination of bla OXA−23 on the Tn2006 in CRAB isolates in Baghdad, Iraq. It appears that this transposon is widespread in GC1 and 2 isolates as in the other parts of the world. Interestingly, one GC1 and one GC2 isolate from Iraq were found to be susceptible to carbapenem while the isolates belonging to GC1 and GC2 have so far rarely been found to be susceptible to carbapenem globally.

Objective To investigate the effect of different antibacterial agents combined with tigecycline in patients with multidrug-resistant Acinetobacter baumannii (MDRAB)-related ventilator-associated pneumonia (VAP), and to provide options for better treatment of the disease in clinical practice. Methods A retrospective analysis was performed for the clinical data of the patients with MDRAB-related VAP who were admitted from January 2016 to August 2023 in Qingdao municipal Hospital, and according to the treatment regimen, they were divided into tigecycline group (group A) with 56 patients, cefoperazone-sulbactam combination therapy group (B group) with 42 patients, and carbapenem combination therapy group (group C) with 24 patients. The three groups were compared in terms of infection and related outcome measures. Results There were no significant diffe-rences in the type of pathogene infected and infection sites between the three groups (P>0.05). Groups B and C had a significantly higher bacterial clearance rate than group A (χ2=5.38,4.48,P0.05). Conclusion Tigecycline combined with cefoperazone-sulbactam or carbapenem achieves a higher bacterial clearance rate than tigecycline alone in MDRAB-related VAP, and combined medication is a relatively good treatment option.

Abstract 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.

Abstract 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.

Abstract Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major human pathogen and a research priority for developing new antimicrobial agents. CRAB is a causative agent of a variety of infections in different body sites. One of the manifestations is catheter-associated urinary tract infection, which exposes the bacteria to the host’s urine, creating a particular environment. Exposure of two CRAB clinical isolates, AB5075 and AMA40, to human urine (HU) resulted in the differential expression levels of 264 and 455 genes, respectively, of which 112 were common to both strains. Genes within this group play roles in metabolic pathways such as phenylacetic acid (PAA) catabolism, the Hut system, the tricarboxylic acid (TCA) cycle, and other processes like quorum sensing and biofilm formation. These results indicate that the presence of HU induces numerous adaptive changes in gene expression of the infecting bacteria. These changes presumably help bacteria establish and thrive in the hostile conditions in the urinary tract. These analyses advance our understanding of CRAB’s metabolic adaptations to human fluids, as well as expand knowledge on bacterial responses to distinct human fluids containing different concentrations of human serum albumin (HSA).

Abstract Acinetobacter baumannii (AB) has emerged as a major pathogen in vulnerable and severely ill patients. It remains unclear whether early mortality (EM) due to AB bacteremia is because of worse clinical characteristics of the infected patients or the virulence of the pathogen. In this study, we aimed to investigate the effect of AB virulence on EM due to bacteremia. This retrospective study included 138 patients with AB bacteremia (age: ≥ 18 years) who were admitted to a tertiary care teaching hospital in South Korea between 2015 and 2019. EM was defined as death occurring within 7 days of bacteremia onset. The AB clinical isolates obtained from the patients’ blood cultures were injected into 15 Galleria mellonella larvae each, which were incubated for 5 days. Clinical isolates were classified into high- and low-virulence groups based on the number of dead larvae. Patients’ clinical data were combined and subjected to multivariate Cox regression analyses to identify the risk factors for EM. In total, 48/138 (34.8%) patients died within 7 days of bacteremia onset. The Pitt bacteremia score was the only risk factor associated with EM. In conclusion, AB virulence had no independent effect on EM in patients with AB bacteremia.

Summary: Background: The continuous emergence of multidrug-resistant (MDR) Acinetobacter baumannii (Ab) strains poses further challenges in its control and clinical management. It is necessary to decipher the mechanisms underlying the high mortality of Ab infections to explore unconventional strategies for controlling outbreaks of drug-resistant infections. Methods: The immune responses of Ab sepsis infection were investigated using flow cytometry, RNA-seq, qRT-PCR, and ELISA and scRNA-seq. The detailed pathways mediating Ab immune responses were also depicted and a specific therapy was developed based on the understanding of the mechanisms underlying Ab-induced cytokine storms. Findings: The results highlighted the critical role of alveolar and interstitial macrophages as targets of Ab during the infection process. These cells were found to undergo polarization towards the M1 phenotype, triggering a cytokine storm that eventually caused the death of the host. The polarization and excessive inflammatory response mediated by macrophages were mainly regulated by the TLR2/Myd88/NF-κB signaling pathway. Suppression of Ab-triggered inflammatory responses and M1 polarization by the drug naproxen (NPXS) was shown to confer full protection of mice from lethal infections. Interpretation: The findings in this work depict the major mechanisms underlying the high mortality rate of Ab infections and highlight the clinical potential application of anti-inflammatory drugs or immunosuppressants in reducing the mortality of such infections, including those caused by MDR strains. Funding: Funding sources are described in the acknowledgments section.

Identification of unique essential bacterial genes is important for not only the understanding of their cell biology but also the development of new antimicrobials. Here, we report a previously unrecognized core component of the Acinetobacter baumannii divisome. Our results reveal that the protein, termed Aeg1 interacts with multiple cell division proteins, including FtsN, which is required for components of the divisome to localize to the midcell. We demonstrate that the FtsAE202K and FtsBE65A mutants effectively bypassed the need of Aeg1 by A. baumannii, as did the activation variants FtsWM254I and FtsWS274G. Our results suggest that Aeg1 is a cell division protein that arrives at the division site to initiate cell division by recruiting FtsN, which activates FtsQLB and FtsA to induce the septal peptidoglycan synthase FtsWI. The discovery of the new essential cell division protein has provided a new target for the development of antibacterial agents.

Background: Rampant and irrational use of antibiotics led to antimicrobial resistance in intensive care units, directly influencing the clinical outcome. The prior introduction of antibiotics, especially broad-spectrum antibiotics, has been identified as a leading cause of hospital-acquired pneumonia. The present study aims to examine the existing scenario of antibiotic resistance due to multidrug-resistant organisms that are detected in mechanically ventilated patients. Methods: This cross-sectional study was conducted in the department of Microbiology of a tertiary care hospital in Central India. A total of 410 endotracheal secretions were collected. The endotracheal aspirate of adult patients admitted to the medicine intensive care unit and on mechanical ventilation was received at the microbiology laboratory for processing by standard bacteriological techniques. Drug susceptibility testing was done using the Kirby-Bauer disc diffusion method according to the indications mentioned in Clinical and Laboratory Standards Institute 2021. Results: Out of 410 collected endotracheal secretion samples, 332 (81 %) samples demonstrated bacterial growth. A total of 265 (80%) cases fulfilled the inclusion criteria. From 265 samples, 92 (34.7 %) patients were clinically and microbiologically confirmed as cases of ventilator-associated pneumonia. Over eighty percent of gram-negative bacilli were multidrug-resistant strains (Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa). Conclusion: Real understanding of multidrug-resistant pathogens, early isolation as well as avoiding long-term antibiotic intake can reduce mortality levels currently linked with late-onset ventilator-associated pneumonia.

Background:The antimicrobial resistance of Acinetobacter baumannii is of major concern. It is one of the commonly distributed nosocomial pathogens, and its strains are frequently reported to demonstrate resistance to the most routinely prescribed antibiotics in varying degrees.Objective:This study aimed to detect the inhibitory effect of chamomile extract against the efflux pump of A. baumannii.Materials and Methods:Clinical samples (125) were collected from different sites (urine, sputum, wound, and burn swabs), followed by A. baumannii isolation and identification, and detection of tetracycline susceptibility test by disk-diffusion. Later on bacterial efflux pump activity was detected by ethidium bromide cartwheel assay and water extract of chamomile was used as an inhibitor of efflux pump A. baumannii.Results:The percentage of A. baumannii isolation 23/125 (18.4%) that distributed as 25% isolates were obtained from sputum, 17.9% isolates from burns, whereas 16% and 12.5% isolates from urine and wounds respectively. It showed various resistances against different members of the three generations of tetracyclines, with the highest resistance against minocycline 47.8% followed by resistance to tetracycline and doxycycline as 43.5% and 39%, respectively. Efflux pump was detected in all cases, water extract of chamomile showed a significant inhibitory effect especially at 80 mg/mL concentration.Conclusion:Efflux pump is an important mechanism for tetracycline resistance among A. baumannii isolates, and the watery extract of chamomile can be considered a prompt inhibitor for this pump.

Abstract Colistin- and carbapenem-resistant Acinetobacter baumannii is a serious multidrug resistant (MDR) bacterium in clinical settings. Discovery of new antibacterial drugs against MDR is facing multiple challenges in drug development. Combination of known antibiotics with a robust adjuvant might be an alternative effective strategy for MDR treatment. In the study herein, we report an antibiotic adjuvant activity of a natural compound panduratin A from fingerroot (Boesenbergia rotunda) as a potent adjuvant to colistin. The present study investigated the antibiotic adjuvant effect of panduratin A against 10 colistin- and carbapenem-resistant A. baumannii. Antibacterial activities were tested by broth microdilution method. Biofilm assay was used to determine the efficacy of panduratin A in biofilm formation inhibition on two representative strains Aci46 and Aci44. Genomic and transcriptomic analyses of colistin- and carbapenem-resistant A. baumannii strains were used to identify potential resistance and tolerance mechanism in the bacteria. Panduratin A-colistin combination showed an increased effect on antibacterial in the A. baumannii. However, panduratin A did not improve the antibacterial activity of imipenem. In addition, panduratin A improves anti-biofilm activity of colistin against Aci44 and Aci46, the colistin- and carbapenem-resistant A. baumannii. Panduratin A markedly enhances bactericidal and anti-biofilm activity of colistin against colistin- resistant A. baumannii. Based on genome comparisons, single nucleotide polymorphism (SNP) patterns in six genes encoding biofilm and lipid A biosynthesis were shared in Aci44 and Aci46. In Aci44, we identified a partial sequence of pmrB encoding a polymyxin resistant component PmrB, whereas a full length of pmrB was observed in Aci46. RNA-seq analyses of Aci44 revealed that panduratin A-colistin combination induced expression of ribosomal proteins and oxidative stress response proteins, whereas iron transporter and MFS-type transporter systems were suppressed. Panduratin A-colistin combination could promote intracellular reactive oxygen species (ROS) accumulation could lead to the cidal effect on colistin-resistant A. baumannii. Combination of panduratin A and colistin showed a significant increase in colistin efficacy against colistin- resistant A. baumannii in comparison of colistin alone. Genomic comparison between Aci44 and Aci46 showed mutations and SNPs that might affect different phenotypes. Additionally, based on RNA-Seq, panduratin A-colistin combination could lead to ROS production and accumulation. These findings confirmed the potency of panduratin as colistin adjuvant against multidrug resistant A. baumannii.

Background and Aim: Multi-drug resistant (MDR) Acinetobacter baumannii is a prevalent hospital pathogen. Antimicrobial peptides (AMPs), such as Oncorhyncin II, have been proposed for treating MDR pathogens. This study aimed to assess the antibacterial activity of recombinant protein Oncorhyncin II against Acinetobacter baumannii (ATCC19606) under in vitro conditions. Methods: In this experimental study, the gene construct pET32a-oncorhyncin II was transferred to Escherichia coli BL21 (DE3) for expressing the recombinant Oncorhyncin II protein. Purification was optimized using nickel affinity chromatography (Ni-NTA), and the peptide's efficacy was evaluated by determining the minimum inhibitory concentration (MIC), bactericidal kinetics, and growth kinetics against Acinetobacter baumannii (ATCC19606). Results: The recombinant Oncorhyncin II protein was successfully expressed in E. coli BL21 (DE3) and purified with over 70% purity. The MIC assay confirmed effective antibacterial activity of Oncorhyncin II against Acinetobacter baumannii at a concentration of 95.87 μg/ml. At 2x MIC, Oncorhyncin II led to a rapid reduction in viable cell count and decreased turbidity of the bacterial inoculum in bactericidal and growth kinetics assessments. Conclusion: The produced recombinant Oncorhyncin II exhibited potent antibacterial activity against Acinetobacter baumannii. These findings can contribute to the development and production of novel antimicrobial drugs for treating infections caused by Acinetobacter baumannii.

Background: The multidrug-resistant and carbapenem-resistant Acinetobacter baumannii strains are an increasing global concern. The primary cause of carbapenem resistance in A. baumannii is production of various beta-lactamases with versatile hydrolytic capacities. The present study investigates the prevalence of different carbapenemases among clinical isolates of carbapenem-resistant A. baumannii from a tertiary care teaching hospital in Kerala, India. Methods: Non-duplicate isolates from sputum, endotracheal aspirate, pus, urine, and blood samples were included in the study. Isolate identification and antibiotic susceptibility testing of the isolates were done using vitek 2 system. A conventional polymerase chain reaction was used to detect the carbapenemase-encoding genes in the isolates. Results: A total of the 126 isolates studied, among these 105 (83.3%) isolates were from intensive care unit patients and 21(16.6%) were from non-ICU inpatients. Most of the isolates were obtained from respiratory specimens-78(61.9%) followed by pus-33(26.2%), urine-12(9.5%) and blood- 3(2.4%). The prevalence of carbapenemase genes were as follows:blaOXA-51(n=126, 100%) blaOXA-23 (n=98, 77.7%), blaOXA-58 (n=7, 5.6%), blaNDM (n=66, 52.4%), blaIMP (n=26, 20.6%), and blaVIM (n=20, 15.9%). Among the total isolates 78 (61.9%) isolates harbored metallo-beta-lactamase genes, 47(37.3%) isolates harboured a single carbapenemase gene, while 69(54.8%) isolates harbored two or more genes. Conclusion: This study reveals a higher prevalence of metallo-beta lactamases and the co-occurrence of multiple carbapenemase genes in Carbapenem resistant A. baumannii isolates.

Introduction: , renowned for its exceptional multidrug resistance and its role as a prevalent nosocomial pathogen, poses a formidable challenge to conventional antibiotic therapies. The primary objective of this investigation was to evaluate the efficacy of Secapin, an antimicrobial peptide, against multidrug-resistant (MDR) . Furthermore, the mechanisms underlying Secapin’s antibacterial and antibiofilm activities were elucidated.Methods: The antimicrobial and antibiofilm effectiveness of Secapin against MDR was assessed through a series of experiments. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Secapin were determined using established protocols. Time-kill kinetic analysis was performed to assess the concentration-dependent bactericidal effect of Secapin. Additionally, the capacity of Secapin to impede biofilm formation and eradicate biofilms was investigated. Hemolytic potential was evaluated using human red blood cells, while mammalian cell viability was examined at varying Secapin concentrations.Results: Secapin exhibited robust bactericidal activity at minimal concentrations, with an MIC of 5 µg/mL and an MBC of 10 µg/mL against MDR . The time-kill kinetic analysis confirmed the concentration-dependent efficacy of Secapin in diminishing bacterial viability. Moreover, Secapin demonstrated the ability to prevent biofilm formation and eliminate established biofilms. Notably, Secapin exhibited no hemolytic activity and preserved mammalian cell viability up to a concentration of 100 µg/mL.Conclusion: These findings underscore the substantial potential of apin as a potent agent against multidrug-resistant , showcasing its efficacy in both antibacterial and antibiofilm capacities. The favorable attributes of Secapin, characterized by its minimal hemolytic effects and high mammalian cell viability, position it as a promising contender in the fight against antibiotic resistance.

Background/Aim: Treatment of infections caused by biofilm-producing multidrug-resistant (MDR) pathogens represents a huge global problem due to primary antimicrobial multi-resistance enhanced by reduced penetration of antibiotics in the biofilm-embedded bacteria. The aim of this study was to determine the capacity of biofilm production among MDR Acine-tobacter baumannii (A. baumannii) isolates obtained from different clinical specimens and to evaluate the inhibitory effect of selenium nanoparticles (SeNPs) coated with cationic polymer cetyltrimethylammonium bromide (CTAB) on the biofilm formation. Methods: Antimicrobial effect of antibiotics (meropenem, imipenem, gentamicin, amikacin, ciprofloxacin, levofloxacin and trimethoprim-sulfa-methoxazole) was determined by disk-diffusion assay, while sensitivity to colistin was determined with E test. All 60 isolates were tested on biofilm production in microtiter plates with crystal violet dye. Minimal biofilm inhib-itory concentration (MBIC) of SeNPs was tested in order to prevent biofilm formation in microtiter plates. Results: All tested clinical isolates were classified as MDR (n = 60) and extensively drug-resistant (XDR, n = 60). Out of the total 60 isolates, 55 isolates (92 %) showed the ability for biofilm formation, with the majority of them classified as strong (42 %) and moderate (42 %) biofilm producers. MBIC values of SeNPs for 55 biofilm-producing isolates ranged from 0.07 to 1.25 mg/mL. Strong biofilm producers had statistically higher MBIC (0.15 mg/mL) in correlation to other biofilm-producing isolates (0.07 mg/ mL). There was no correlation between invasiveness of isolates with biofilm production and MBIC values. Conclusion: Presented results are very promising and interesting especially in nanotechnology and medical fields, while SeNPs with the addition of cationic surfactant inhibit biofilm formation of MDR A. baumannii clinical isolates.

Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, dan Escherichia coli merupakan kelompok critical-priority bacteria yang telah mengalami multi drug resistant (MDR) dan sering ditemukan di Intensive Care Unit (ICU). Isolat bakteri-bakteri berjumlah lebih dari 75% mengalami MDR di ICU sebuah rumah sakit umum daerah di Bali, Indonesia. Penggunaan antibiotik yang tinggi berkaitan dengan tingkat resistensi bakteri terhadap antibiotik. Pola resistensi bakteri terhadap antibiotik dapat berbeda di setiap wilayah yang disebabkan oleh adanya perbedaan lingkungan dan perbedaan tingkat penggunaan antibiotik di wilayah tersebut. Penelitian ini bertujuan untuk mengetahui tren penggunaan antibiotik sistemik, pola resistensi dan hubungan antara tingkat penggunaan dengan persentase resistensi bakteri terhadap antibiotik pada kelompok critical-priority bacteria di ICU rumah sakit “X” provinsi Bali. Penelitian ini merupakan penelitian ekologikal yang menggunakan data sekunder selama tahun 2017-2019. Analisis tren penggunaan antibiotik dianalisis menggunakan time series analysis. Hubungan antara tingkat penggunaan antibiotik dan persentase resistensi bakteri prioritas kritis dianalisis dengan regresi linier. Hasil penelitian menunjukkan bahwa antibiotik gentamisin, amikasin, dan siprofloksasin mengalami peningkatan tren penggunaan sedangkan ampisilin, ampisilin-sulbaktam, seftazidim, dan meropenem mengalami penurunan tren penggunaan. Time series analysis menunjukkan penggunaan antibiotik yang fluktuatif. Selain itu, didapatkan bahwa A. baumannii masuk dalam dua kategori fenotipik CDC yaitu, carbNS_Acine dan MDR_Acine sedangkan K. pneumoniae masuk dalam kategori ESCklebsiella. Tingkat penggunaan antibiotik sistemik di ICU dengan persentase resistensi E. coli, K. pneumoniae, dan P. aeruginosa di ICU (p0,05).

Abstract Background and Objective The emergence and widespread dissemination of antibiotic resistance in A. baumannii, has become a globally challenge. The increasing hospital outbreaks by multi-drug resistant (MDR) A. baumannii strains, shows the necessity of continuous monitoring to find sources of resistant strains in hospitals. This study aimed to identify the presence of class 1 integrons and metallo-β-lactamase (MBL) related genes in A. baumannii isolates from hospital environment. Methods In order to identify A. baumannii isolates, a total of 297 environmental samples were collected from burn wards and intensive care units (ICUs) of two university hospitals. Resistance to common antibiotics was studied by disk diffusion method and microbroth dilution assay was used to determine the minimum inhibitory concentrations (MICs) of imipenem, colistin and tigecycline. The A. baumannii isolates were studied by polymerase chain reaction (PCR) for the presence of class 1 integrons (intI1, intl CS) and metallo-β-lactamases (MBLs) (bla IMP, bla VIM, bla NDM) genes. Results A. baumannii was identified in 68/297 (22.9%) of hospital environment. All A. baumannii strains were multidrug-resistant (MDR), but none of them were resistant to colistin, tigecycline and ampicillin-sulbactam. All (100%) and 38 (95.0%) of A. baumannii isolates from ICUs and burn wards were imipenem resistant respectively. Class 1 integrons was identified in 30/40 (75.0%) and 23/28 (82.1%) isolates from burn wards and ICUs respectively. Two different types of gene cassettes were identified, which included: arr-2, ereC, aadA1, cmlA5 and arr2, cmlA5. MBL genes including bla VIM and bla IMP were detected in 26/28 (92.8%), 27/28(96.4%) and 39/40 (97.5%) and 31/40 (77.5%) of the isolates from the ICUs and the burn wards respectively. None of the isolates contained the bla NDM−1 gene. Conclusion The findings of the present study showed that the isolation rate of MBL producing carbapenem-resistant A. baumannii (CRAB) was relatively high in the environmental surface of burn wards and ICUs, which can be considered as a potential source of outbreaks in hospitalized patients.

The continued rise in antimicrobial resistance poses a serious threat to public health worldwide. The use of phages that can have bactericidal activity without disrupting the normal flora represents a promising alternative treatment method. This practice has been successfully applied for decades, mainly in Eastern Europe, and has recently been used as an emergency therapy for compassionate care in the United States. Here, we provide a comprehensive review of the pre-clinical and clinical applications of phage therapy concerning three major Gram-negative pathogens: Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The advantages and the challenges of expanding the usage of phages as an alternative or adjunctive treatment for antimicrobial-resistant bacterial infections are discussed. We emphasize the virologic complexities of using the highly adaptable phage populations as molecular tools, along with antibiotic chemical compounds, to effectively combat rapidly coevolving pathogenic bacteria in the host microenvironment. Pre-clinical studies, isolated clinical reports and a few randomized clinical trials have shown that bacteriophages can be effective in treating multidrug-resistant bacterial infections. The ability of some phages to revert the resistance against antibiotics, and possibly also against the human complement and other phages, appears to be a great advantage of phage therapy despite the inevitable emergence of phage-resistant strains. Bacteriophages (or specific phage-derived products) can enhance antimicrobial efficacy by reducing bacterial virulence via the alteration of basic bacterial structures, primarily of the cellular wall and membrane. Although several issues remain open regarding their effective clinical application, it appears that phage-based therapeutics in combination with antibiotics can provide an effective solution to the spread of antimicrobial resistance.

Objectives: The aim of this study was to prepare monoclonal antibodies (mAbs) that broadly target Acinetobacter baumannii and protect against infection by multi-drug-resistant (MDR) A. baumannii from different sources. Methods: mAb 8E6 and mAb 1B5 were prepared by sequentially immunizing mice with a sublethal inoculation of three heterogeneous serotypes of pan-drug-resistant (PDR) A. baumannii, ST-208, ST-195, and ST-229. Results: The cross-recognition of heterogeneous bacteria (n = 13) by two mAbs and potential targets was verified, and the in vitro antibacterial efficacy of mAbs was assessed. The median killing rate of mAb 8E6 against A. baumannii in the presence of complement and dHL-60 cells was found to be 61.51%, while that of mAb 1B5 was 41.96%. When only dHL-60 cells were present, the killing rate of mAb 8E6 was 65.73%, while that of mAb 1B5 was 69.93%. We found that mAb 8E6 and mAb 1B5 broadly targeted MDR A. baumannii on the ATP synthase complex and were equipped with an antibacterial killing ability by enhancing the innate immune bacteriolytic effect of ST-208 and ST-195 strains. Both monoclonal antibodies were validated to protect against respiratory infection at 4 and 24 h via enhancing the release of innate immune substances and inflammatory cytokines, effectively shortening the disease period in mice. Conclusions: mAb 8E6 and mAb 1B5 significantly enhanced the opsonization process of phagocytosis against A. baumannii strains prevalent in southern China by targeting ATP synthase antigens thereof, resulting in protective effects in mice.

Abstract Background and Aims Emergence of multidrug resistance in non‐fermenting Gram‐negative bacilli is a threat to public health. Combination therapy is a strategy for the treatment of antibiotic‐resistant infections. Methods In this cross‐sectional study, a total of 63 nonduplicate clinical isolates of Acinetobacter baumannii and Pseudomonas aeruginosa were collected from various specimens. Identification of bacterial isolates was performed by phenotypic and molecular tests. Antibiotic susceptibility patterns and detection of β‐lactamase genes were determined using the broth microdilution and polymerase chain reaction (PCR) techniques, respectively. Then, the combined effects analysis was determined by the checkerboard method. Based on the status of resistance to carbapenems (imipenem and meropenem), 25 isolates of each genus were selected for further investigation. Results For A. baumannii, blaOXA‐23, blaOXA‐58, and blaOXA‐48 genes were positive in 21 (84%), 17 (68%), and 11 (44%) of isolates, respectively. In P. aeruginosa isolates, blaVIM was the most common gene (44%) and other genes including blaIMP, blaNDM, and blaOXA‐23 were found in nine (36%), six (24%), and three (12%) isolates, respectively. Meropenem (MER)‐tigecycline (TIG) had a significant synergistic effect against 20 (80%) A. baumannii (p value

Summary: Background: The current pipeline for new antibiotics fails to fully address the significant threat posed by drug-resistant Gram-negative bacteria that have been identified by the World Health Organization (WHO) as a global health priority. New antibacterials acting through novel mechanisms of action are urgently needed. We aimed to identify new chemical entities (NCEs) with activity against Klebsiella pneumoniae and Acinetobacter baumannii that could be developed into a new treatment for drug-resistant infections. Methods: We developed a high-throughput phenotypic screen and selection cascade for generation of hit compounds active against multidrug-resistant (MDR) strains of K. pneumoniae and A. baumannii. We screened compound libraries selected from the proprietary collections of three pharmaceutical companies that had exited antibacterial drug discovery but continued to accumulate new compounds to their collection. Compounds from two out of three libraries were selected using “eNTRy rules” criteria associated with increased likelihood of intracellular accumulation in Escherichia coli. Findings: We identified 72 compounds with confirmed activity against K. pneumoniae and/or drug-resistant A. baumannii. Two new chemical series with activity against XDR A. baumannii were identified meeting our criteria of potency (EC50 ≤50 μM) and absence of cytotoxicity (HepG2 CC50 ≥100 μM and red blood cell lysis HC50 ≥100 μM). The activity of close analogues of the two chemical series was also determined against A. baumannii clinical isolates. Interpretation: This work provides proof of principle for the screening strategy developed to identify NCEs with antibacterial activity against multidrug-resistant critical priority pathogens such as K. pneumoniae and A. baumannii. The screening and hit selection cascade established here provide an excellent foundation for further screening of new compound libraries to identify high quality starting points for new antibacterial lead generation projects. Funding: BMBF and GARDP.

Objective·To explore the mechanism of changes in resistance to meropenem (MEM), a carbapenem drug, in Acinetobacter baumannii (A. baumannii) cultured in different antibiotic concentrations.Methods·Through changing the MEM concentration and other culture conditions of the standard sensitive strain of A. baumannii ATCC19606 and the clinical drug-resistant strain AB.2014, the derived strains with different levels of MEM-resistance were induced. The growth curves of all the stains were detected. DNA and RNA of them were extracted. PCR was used to analyze the expression of carbapenemase genes, including IMI, KPC, GES-1, IMP, VIM, NDM-1, OXA23, OXA24, OXA51, and OXA58. Real-time fluorescent quantitative PCR (RT-qPCR) was used to analyze the expression levels of the carbapenemase gene (OXA51), efflux pump genes (adeB, adeG, and adeJ), pore protein genes (carO, omp33-36, and oprC) and the penicillin-binding protein gene (ponA) in the A. baumannii strains with different resistance to MEM, of which the differential gene enrichment was also detected by whole genome sequencing and bioinformatics tools.Results·The 11 derived strains of ATCC19606 and AB.2014 with different levels of resistance to MEM were obtained, of which the minimum inhibitory concentrations (MIC) were 1‒128 μg/mL. The growth rates and peak values of ATCC19606 and its derivatives decreased with the increase of drug resistance, but AB.2014 and its derivatives did not show this trend. ATCC19606 and its derived strains expressed 3 carbapenemase genes, i.e., OXA51, VIM and IMP, while AB.2014 and most of its derived strains expressed 4 carbapenemase genes, i.e., OXA23, OXA51, VIM and IMP, with only one sensitized derivative of AB.2014 losing OXA23 gene. RT-qPCR results showed that only in ATCC19606 and its drug-resistant derivatives, the expression level of oprC gene decreased with the increase of drug resistance, and the expression levels of most drug-resistant genes were consistent with the changes of drug resistance levels of the strains. Bioinformatics analysis indicated that the differential genes among different ATCC19606 strains were mainly enriched in the siderophore uptake transmembrane transporter activity, cell outer membrane, bacterial secretion system and quorum sensing, while those among AB.2014 strains were mainly enriched in cell outer membrane, cellular response to chemical stimulus, atrazine degradation and RNA polymerase.Conclusion·The environmental pressure from carbapenems will cause the change of drug resistance of A. baumannii with the involvement of the genes of carbapenemases, efflux pumps, pore proteins and penicillin-binding proteins. The loss of carbapenemase gene OXA23 may lead to the desensitization of drug-resistant A. baumannii strains to carbapenems.

Background: The emergence of coronavirus disease in 2019 (COVID-19) appears to be having an impact on antibiotic resistance patterns. Specific circumstances during the COVID-19 era may have played a role in the spread of antimicrobial resistance (AMR). This study aimed to look at the changes in AMR patterns of Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii at Al-Zahra Hospital. Materials and Methods: From March 2021 to January 2023, 3651 clinical samples were collected from patients hospitalized at Isfahan’s Al-Zahra Hospital. The Clinical and Laboratory Standards Institute recommended procedures for detecting gram-negative bacteria and assessing antibiotic susceptibility were used. We divided the information into three years. Results: Highest resistance rates were seen in A. baumannii to Ciprofloxacin (98.0%) and Ampicillin-Sulbactam (97.0%). For P. aeruginosa the resistance rate for Ceftazidime (36.1), Levofloxacin (37.8), and Meropenem (47.1) dropped seriously in 2022. Conclusion: During the second year of the pandemic in central Iran, all three species studied showed rising rates of AMR. This can be attributable to two peaks within Iran on May 6, 2021 and August 27, 2021. The results of this study show that P. aeruginosa, K. pneumoniae, and A. baumannii bacteria in central Iran have a higher level of antibiotic resistance than previously studied strains before the pandemic.

Blood and surveillance cultures from an injured service member from Ukraine grew Acinetobacter baumannii, Klebsiella pneumoniae, Enterococcus faecium, and 3 distinct Pseudomonas aeruginosa strains. Isolates were nonsusceptible to most antibiotics and carried an array of antibiotic resistant genes, including carbapenemases (blaIMP-1, blaNDM-1, blaOXA-23, blaOXA-48, blaOXA-72) and 16S methyltransferases (armA and rmtB4).

Introduction: Acinetobacter baumannii (A. baumannii) is a non-fermentative gram-negative coccobacillus that shows high resistance to antimicrobial compounds. Biofilm formation is one of the essential features of many Acinetobacter species that leads to high antibiotic resistance. This study aimed to evaluate the ability of biofilm formation and determine the antibiofilm activity of chitosan nanoparticles in clinical isolates of A. baumannii. Material & Methods: This descriptive cross-sectional study was conducted in 2021 and investigated 100 isolates collected from different hospitals. Microscopic, biochemical, and molecular tests were performed to identify the bacteria. The antibiotic resistance pattern of the isolates was evaluated by the disk diffusion method against 10 antibiotics, and the ability to produce biofilm was evaluated by microtiter plate method. Subsequently, 16SrRNA and CsuA genes were identified by multiplex-PCR molecular methods. After the preparation of chitosan nanoparticles and determination of MIC concentration, antibiofilm activity was measured by plate microtiter, and Real-Time PCR was used to examine the expression of the CsuA gene involved in biofilm. Findings: In this study, out of 100 isolates examined, 29 isolates were confirmed as A. baumannii. Among 29 isolates, ceftazidime had the highest drug resistance (75.86%). The CsuA gene was detected in 51.72% of the isolates. Moreover, using a microtiter plate and Real-Time PCR, the level of antibiotic activity of chitosan nanoparticles was determined at a significant level of P

Abstract Background The lack of appropriate vaccines is an obstacle to the effective management of A. baumannii infections. Peptide vaccines offer an attractive and promising preventive strategy against A. baumannii. Objective In this study, we identified specific T cell epitopes of A. baumannii outer membrane protein K (OMPK) using comprehensive bioinformatics and detailed molecular docking analysis. Methods Both class-I and class-II T cell epitopes of A. baumannii OMPK were predicted by three tools namely IEDB, SYFPEITHI, and ProPred. The predicted epitopes were shortlisted based on several analyses including prediction scoring, clustering, exclusion of human similarity, considering immunogenicity and cytokine production, and removal of toxic and/or allergen epitopes. The epitopic peptides with high prediction scores and appropriate properties containing both class-I and class-II T cell epitopes were selected. Two of these class I/II epitopic peptides were chosen for molecular docking studies and assessing their physicochemical properties as vaccine candidates. Results The results showed many T-cell epitopes of OMPK that could be evaluated for possible immunogenicity. Two of these epitopes (containing both class-I and II epitopes) had high prediction scores, were predicted by several tools, attached to several HLAs, and had the best docking score. They had different physicochemical properties and were conserved among Acinetobacter species. Discussion We identified the A. baumannii OMPK high immunogenic class-I and class-II T cell epitopes and introduced two promising high immunogenic peptides as vaccine candidates. It is recommended to perform in vitro/in vivo investigation of these peptides to determine their true efficacy and efficiency.

Abstract Background We investigated the presence of heteroresistance against both tigecycline and colistin in Acinetobacter baumannii and then evaluated the effectiveness of combined antibiotic treatment given the existence of discrete tigecycline- and colistin-resistant subpopulations. Methods We performed population analysis profiling (PAP) to evaluate the degree of composite heteroresistance in A. baumannii isolates, with the extent of this resistance quantified using subsequent antibiotic susceptibility testing. We then evaluated the amino acid sequence of PmrBAC and the relative mRNA expression levels of pmrB. Finally, we investigated the combined antibiotic efficacy of tigecycline and colistin in multiple-heteroresistant isolates using dual PAP and in vitro time-killing assays. Results All tigecycline-heteroresistant A. baumannii isolates, with the exception of one colistin-resistant isolate, were also heteroresistant to colistin. Evaluations of the colistin-resistant subpopulations revealed amino acid alterations in PmrA and PmrB and increased expression of pmrB. All tigecycline-resistant subpopulations were susceptible to colistin, and all colistin-resistant subpopulations were susceptible to tigecycline. Dual PAP analysis using tigecycline and colistin showed no heteroresistance, and in vitro time-killing assays revealed that a combination of these two antibiotics effectively eliminated the bacterial cells. Conclusion Our results suggest that multiple heteroresistance to tigecycline and colistin is highly prevalent among A. baumannii clinical isolates and that these resistant subpopulations exist independently in single multiple heteroresistant isolates. Therefore, our findings may explain the success of combined antibiotic therapies in these infections.

Background: A. baumannii is a gram-negative pathogen that has become one of the most important challenges in the world due to its high antibiotic resistance, and today many efforts are being made to treat infections caused by it. In recent years, there have been many concerns about increasing resistance to the beta-lactam antibiotic, carbapenem. Because resistance to these antibiotics greatly narrows the treatment options for the infections. The main source of carbapenem resistance in A. baumannii is the production of class D carbapenemase enzymes. Methods: In this study, 27 plant ligands that have been shown to have antibacterial effects against A. baumannii and other resistant bacteria were selected. The chemical structure of the ligands and the three-dimensional structure of carbapenemase OXA-58 were extracted. The requirements of oral consumption of ligands were examined and ligand and OXA-58 docking were performed. 9 ligands including baicalein, berberine, curcumin, ellagic acid, epicatechin, honokiol, magnolol, norwogonin, and thymol, which met the requirements of Rule 5 and had better binding affinity than 6-alpha- hydroxymethyl penicillanate were selected. Redocking with a focus on the active position was performed by AutoDock software. Results: The amino acids involved in the hydrogen bonding of an antibiotic-representative ligand to the receptor were identified. Ligands that bind to at least one of these amino acids at the binding site by hydrogen bond were selected. Pharmacological and toxicity studies were performed and finally, the epicatechin ligand was introduced as the best ligand. Conclusion: Plant ligands can be further investigated as promising antibiotic adjuvants and used in the future.

Background. The coronavirus disease 2019 (COVID-19) pandemic placed an unprecedented strain on intensive care units (ICUs) in South Africa. Infection prevention and control (IPC) strategies were highlighted to minimise the risk to healthcare workers and for the protection of patients from contracting hospital-acquired infections (HAIs). During the third wave, our institution adopted a shift system to address severe burnout among ICU personnel. We noted an upstroke in the occurrence of HAIs, specifically carbapenem-resistant Enterobacterales (CRE) and multidrug-resistant (MDR) Acinetobacter baumannii. Objectives. To report these outbreaks, compare the rate of CRE and A. baumannii infections with the first COVID-19 wave and to analyse its impact on patient outcomes. Method. We retrospectively analysed data from a prospectively collected registry involving all adult patients with severe COVID-19 admitted to the dedicated COVID-19 ICU from May 2021 to September 2021. Information from the admission database, including the patients’ demographics, comorbidities, laboratory results and length of ICU stay were extracted. Results. Ninety patients were admitted with severe COVID-19 during the third wave. There was an outbreak of both CRE (the majority Klebsiella pneumoniae) and A. baumannii. Furthermore, 18 patients cultured the same CRE organism, and 25 patients cultured the environmental organism A. baumannii. The HAI rate was significantly higher compared with the first wave published data: 59/90 (65.6%) v. 73/363 (20.1%, p

Background and objective: Acinetobacter baumannii is a significant pathogenic bacterium in the health system. The ability to resist antimicrobial drugs and biofilm formation gives the considerable capacity to A. baumannii for existing in a harsh environment, enabling this bacterium to cause hospital-acquired infection. Carbapenem is an important treatment option for severe nosocomial infection and patients infected by multidrug-resistant organisms. The main aim of this study is to detect carbapenemase in isolates, and its association with biofilm formation as well as antibiotic resistance. Methods: Sixty A. baumannii isolates were obtained from several hospital districts in Erbil city. Identification and antimicrobial susceptibility test (AST) of isolates were performed by VITEKII compact system. Phenotypic identification of carbapenem by sCIM also biofilm-forming was detected by 96 well method. Additionally, three antimicrobial agents were used if they were successful in eliminating biofilm formation. . Results: The majority of the isolates were from sputum, accounting 75% and antibiotic susceptibility showed that the isolates are resistant to the most available antibiotics, and significant of the isolates formed strong biofilm. The sensitivity of meropenem, ceftazidime, and ciprofloxacin were employed for ten isolates of A. baumannii after biofilm formation it was found that biofilm cells need more concentration of antibiotic than planktonic cells then phenotypic detection of carbapenem showed that the overall positive values were 30 (50.0%) for sCIM. Conclusion: We revealed that most resistant isolates have a greater capacity for biofilm development than sensitivite isolates. Biofilm-producing strains of A. baumannii cannot be killed with the relatively similar concentration of antimicrobial drugs that are needed to kill planktonic cells.

Multidrug-resistant (MDR) bacteria of the utmost importance are extended-spectrum β-lactamase (ESBL) and carbapenemase-producing Enterobacterales (CRE), carbapenem-resistant Acinetobacter baumannii (CRAB), carbapenem-resistant Pseudomonas aeruginosa (CRPA), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus spp. (VRE). In this study, an evaluation of MDR bacteria in surgical intensive care units in a tertiary referral hospital was conducted. The study aimed to characterize β-lactamases and other resistance traits of Gram-negative bacteria isolated in surgical intensive care units (ICUs). Disk diffusion and the broth dilution method were used for antibiotic susceptibility testing, whereas ESBL screening was performed through a double disk synergy test and an inhibitor-based test with clavulanic acid. A total of 119 MDR bacterial isolates were analysed. ESBL production was observed in half of the Proteus mirabilis, 90% of the Klebsiella pneumoniae and all of the Enterobacter cloacae and Escherichia coli isolates. OXA-48 carbapenemase, carried by the L plasmid, was detected in 34 K. pneumoniae and one E. coli and Enterobacter cloacae complex isolates, whereas NDM occurred sporadically and was identified in three K. pneumoniae isolates. OXA-48 positive isolates coharboured ESBLs belonging to the CTX-M family in all but one isolate. OXA-23 carbapenemase was confirmed in all A. baumannii isolates. The findings of this study provide valuable insight of resistance determinants of Enterobacterales and A. baumannii which will enhance surveillance and intervention strategies that are necessary to curb the ever-growing carbapenem resistance rates.

Bacteria of the genus Acinetobacter, especially Acinetobacter baumannii (Ab), have emerged as pathogens of companion animals during the last two decades and are commonly associated with hospitalization and multidrug resistance. A critical factor for the distribution of relevant strains in healthcare facilities, including veterinary facilities, is their adherence to both biotic and abiotic surfaces and the production of biofilms. A group of 41 A. baumannii isolates obtained from canine and feline clinical samples in Greece was subjected to phenotypic investigation of their ability to produce biofilms using the tissue culture plate (TCP) method. All of them (100%) produced biofilms, while 23 isolates (56.1%) were classified as strong producers, 11 (26.8%) as moderate producers, and 7 (17.1%) as weak producers. A correlation between the MDR and XDR phenotypes and weak or moderate biofilm production was identified. Moreover, the presence of four biofilm-associated genes bap, blaPER, ompA, and csuE was examined by PCR, and they were detected in 100%, 65.9%, 97.6%, and 95.1% of the strains respectively. All isolates carried at least two of the investigated genes, whereas most of the strong biofilm producers carried all four genes. In conclusion, the spread and persistence of biofilm-producing Ab strains in veterinary facilities is a matter of concern, since they are regularly obtained from infected animals, indicating their potential as challenging pathogens for veterinarians due to multidrug resistance and tolerance in conventional eradication measures. Furthermore, considering that companion animals can act as reservoirs of relevant strains, public health concerns emerge.

Multi-drug-resistant (MDR) Acinetobacter baumannii is an opportunistic pathogen associated with hospital-acquired infections. Due to its environmental persistence, virulence, and limited treatment options, this organism causes both increased patient mortality and incurred healthcare costs. Thus, prophylactic vaccination could be ideal for intervention against MDR Acinetobacter infection in susceptible populations. In this study, we employed immunoinformatics to identify peptides containing both putative B- and T-cell epitopes from proteins associated with A. baumannii pathogenesis. A novel Acinetobacter Multi-Epitope Vaccine (AMEV2) was constructed using an A. baumannii thioredoxin A (TrxA) leading protein sequence followed by five identified peptide antigens. Antisera from A. baumannii infected mice demonstrated reactivity to rAMEV2, and subcutaneous immunization of mice with rAMEV2 produced high antibody titer against the construct as well as peptide components. Immunization results in increased frequency of IL-4-secreting splenocytes indicative of a Th2 response. AMEV2-immunized mice were protected against intranasal challenge with a hypervirulent strain of A. baumannii and demonstrated reduced bacterial burden at 48 h. In contrast, all mock vaccinated mice succumbed to infection within 3 days. Results presented here provide insight into the effectiveness of immunoinformatic-based vaccine design and its potential as an effective strategy to combat the rise of MDR pathogens.

Objective To establish an ultra-filtration centrifugation method to purify the outer membrane vesicles (OMVs) of Acinetobacter baumannii(A.baumannii), and to investigate the ability of OMVs to induce inflamma-tion in human monocyte-derired macrophages THP-1. Methods A.baumannii was cultured, and the OMVs were purified from the supernatant of culture medium by ultra-filtration centrifuge,the morphology was observed by transmission electron microscopy. THP-1 cells were incubated with OMVs at the concentration of 5 and 50 μg/mL respectively. The expression of NOD-like receptor protein 3(NLRP3) and caspase-1 were determined by RT-qPCR. The concentration of IL-1β in culture medium supernatant was measured by ELISA. The expression of LC-3Ⅱ and Beclin-1 was examined by Western blot. The activity of caspase-3 was determined by enzyme dynamics assay. The expression of reactive oxygen species (ROS) was determined by flow cytometry. Results A.baumannii OMVs was purified successfully. The OMVs could activate NLRP3 inflammasome, increase the expression of LC-3Ⅱ and Beclin-1 and up-regulate the activity of caspase-3 (PPConclusions OMVs of A.baumannii can significantly activate macrophages NLRP3 inflammasome and induce cell autophagy and apoptosis.

Background: Acinetobacter, measured as an opportunistic pathogen has lately occurred as a vital nosocomial pathogen in the world, frequently relating patients with reduced host defenses. Patients in dangerous cases obtain infections while they are staying in care wards, so the incidence of these infections varies significantly in different individuals and clinical settings. Objectives: This work aims to examine the prevalence of carbapenem-resistance genes among isolates of Acinetobacter baumannii gathered from three hospitals in Iraq. Materials and Methods: A total of 30 isolates of A. baumannii were gathered from different clinical samples from February to July 2022. DNA of all specimens was extracted. Gradient polymerase chain reaction was applied to discover the genes of bla-OXA carbapenemases. Results: The results exhibited a variation of carbapenemase genes in all isolates that had been examined. Although all isolates had at least three genes of carbapenemase that have been tested, the most commonly identified genes in class D β-lactamases were bla OXA-51 and bla OXA-23 which was established in all isolates of A. baumannii 30 (100%) tested. It was also found that nine (30%) of tested isolates had borne the gene of bla OXA-58. No isolate exhibited amplification for the gene of bla OXA-40. Conclusion: The maximum occurrence and prevalence of the genes of OXA β-lactamase in A. baumannii bacteria in Iraqi hospitals were bla OXA-23 and bla OXA-51.

Background: Acinetobacter baumannii can reside in humans without causing infection or symptoms but can opportunistically cause community and nosocomial infections. Few studies from Taiwan have used national-level data to investigate antibiotic resistance rates of A. baumannii infections in the intensive care units (ICUs) of medical centers. Aim: This study determined the number of infection sites of A. baumannii and the resistance rates of carbapenem-resistant A. baumannii (CRAB) infections in ICUs in Taiwan, and identified trends over time, variations of infection site, and factors associated with resistance. Methods: This study used the database provided by Taiwan's Centers for Disease Control. Yearly, Taiwan Nosocomial Infections Surveillance System Surveys from 2008 to 2019 were analyzed, including data on the site of infection and resistance rates of A. baumannii and patient and hospital characteristics. Results: On average, 21 hospitals as medical center/year participated in the survey, and 6803 A. baumannii isolates were identified. All isolates were health care-related infections. The most frequent sites of infection were the urinary tract (50.6%), respiratory tract (19.6%), bloodstream (18.2%), surgical wounds (4.3%), and others (7.4%). Infection rates were the highest in the urinary tract in 2019 (63.6%; P < 0.001). On average, the rate of carbapenem resistance was 66.6% (95% confidence interval: 63.1–70.1) among ICU patients at medical centers. Considerable regional differences were observed, with the highest rates of resistance in the central regions. Higher resistance rates were observed between 2019 and 2020 COVID-19 pandemic (74.2%). Conclusion: This is the first report on the prevalence of health care-related A. baumannii infection in Taiwan in 2008–2019. Several invasive diseases, such as urinary tract infections, are associated with higher rates of carbapenem resistance. The resistance rate of CRAB in Taiwan is exceptionally high. The current big-data-derived findings may inform future surveillance and research efforts in Taiwan.

Introduction: In this study, the antimicrobial activity of biologically synthesized zinc (Zn) and copper (Cu) nanoparticles was investigated on gram-positive and gram-negative bacteria, pathogens, and resistant and common nosocomial infections. Material & Methods: Intially, zinc oxide and copper nanoparticles were synthesized using Xanthomonas campestris and Pseudomonas stutzeri bacteria, respectively. To investigate the effect of different concentrations of nanoparticles on bacteria using the macrodilution method, concentrations of 0.01, 0.1, 0.5, 1, and 1.5% of Zn and Cu nanoparticles (culture medium + nanoparticles) were prepared and were added to the respective bacteria at a concentration of 105 cell/ml. Containers containing treated media (bacteria + nanoparticles) and control media were placed in a shaker incubator. Afterward, the optical density (OD) of treatment and positive control and negative control media were determined. (Ethic code: IR.ILAM.REC.1401.008) Findings: The results of statistical analysis showed that Zn and Cu nanoparticles, at a concentration of 0.5%, were able to remove almost all (100%) Klebsiella pneumoniae, Acinetobacter baumannii, Staphylococcus aureus bacteria and were bacteriostatic at the concentration of 0.1%. Discussion & Conclusion: The results obtained from the determination of antibacterial properties of nanoparticles showed a direct relationship between the concentration of nanoparticles and the percentage of bacterial removal.

ObjectiveThis study aimed to investigate the risk factors affecting the positive detection of Acinetobacter baumannii on the hands in medical staff of hospitals in Shanghai， and provide epidemiological evidence for the prevention and control of nosocomial infections.MethodsThe hands of doctors， nurses and care workers in key departments were sampled every quarter from 2018 to 2020 according to GB 15982‒2012 "Hospital Disinfection and Hygiene Standards". Separation and identification of A. baumannii were followed with sampling shortly. Information about the working years of sampling subjects， the hand sanitizers of which sampling subjects had used and the ingredients and actual using time of the hand sanitizers was collected while sampling. Finally， 709 samples were selected for this research after excluding the unqualified samples.ResultsThe positive detection of the hand samples was 7.05%. The logistic regression model suggested that the department， the time of using hand sanitizer， the hospital grade and occupational category were determinants of A. baumannii positive detection on hands in medical staff. The risk of A. baumannii positive detection in internal medicine department was 2.846 （95%CI：1.402‒5.776） times higher than that in intensive care unit while it was 3.357 （95%CI：1.349‒8.353） times higher in surgery department than that in intensive care unit. Regarding the use of hand sanitizer， the risk of A. baumannii positive detection was 3.076 （95%CI：1.534‒6.168） times higher in the staff used the hand sanitizer over 14 days than in the medical staff used the sanitizer within 14 days. The risk of A. baumannii positive detection in medical worker in secondary hospitals was 2.235（95%CI：1.088‒4.588）times than in tertiary hospitals. The risk of A. baumannii positive detection of care workers was 3.634 （95%CI：1.764‒7.484） times higher than nurses.ConclusionThe positive detection of hand samples was 7.05%. Department， the time of using hand sanitizer， the hospital grade and occupational category were determinants of A. baumannii positive detection on hands in medical staff. It was necessary to improve hand hygiene for medical staff， especially for care worker. Cleaning and disinfection need to be strengthened in internal department and surgery department.

INTRODUCTION: It was aimed to determine the presence of metallo-beta-lactamases (MBL) and oxacillinases (OXA) enzymes in Acinetobacter baumannii complex (ABC) isolates, which show decreased sensitivity to carbapenems isolated from blood cultures and to investigate the relationships of isolates among each other and with European clones (EU) I, II, III. METHODS: The study included ABC isolate which has reduced sensitivity to at least one of either imipenem or meropenem which was isolated from blood samples obtained from 74 patients who were admitted to the hospital between 2008 and 2009. Identification of isolates and their antimicrobial susceptibilities were performed using BD Phoenix Automated System (Becton-Dickinson, USA). OXA and MBL genes were investigated by polymerase chain reaction (PCR). The clonal relationship of the isolates was determined by pulsed-field gel electrophoresis (PFGE) method. RESULTS: MBL genes and blaOXA-24-like gene were not determined in any of the isolates. blaOXA-51-like was detected in all isolates, blaOXA-58-like gene in 32 isolates and blaOXA-23-like gene in 26 isolates. Using PFGE method, it was detected that fifty-five blood isolates carrying the blaOXA23-like and/or blaOXA-58-like gene were clustered under six clusters. The similarity of EU clones with clinical ABC isolates in the clusters was found to be over 90%. DISCUSSION AND CONCLUSION: ABC isolates producing oxacillinase in our hospital; The presence of association with EU clone III, which is reported very rarely in our country, and the detection of possible related isolates with EU clones I and II show the potential for the spread of these clones in our hospital and in our country.

Introduction: In the last 40 years, Acinetobacter baumannii has been among the bacteria known to acquire multiple mechanisms of antibiotic resistance and, as a result, it is now one of the pathogens involved in healthcare-associated infections with multidrug resistant strains. Our study aimed to assess the production of carbapenemases in carbapenem-resistant A. baumannii by means of phenotypic methods and polymerase chain reaction technique (PCR), as well as to appraise the performances of carbapenemase detection by phenotypic tests compared to the PCR approach.

Objective(s): The high resistance rate of Acinetobacter baumannii and the limited number of available antibiotics have prompted a worldwide effort to develop effective antimicrobial agents. Accordingly, identifying single-chain variable fragment antibodies (scFvs), capable of exerting direct antibacterial activity in an immune system-independent manner, may be making immunocompromised patients more susceptible to A. baumannii infections.Materials and Methods: To isolate bactericidal scFvs targeting A. baumannii, we panned a large human scFv phage display library against whole-cell extensively drug-resistant (XDR) A. baumannii strains grown as biofilm or cultured with human blood or human peripheral blood mononuclear cells plus plasma. The binding of scFv-phages to A. baumannii was assessed by the dot-blot assay. Soluble scFvs, derived from the selected phages, were assessed based on their ability to bind and inhibit the growth of A. baumannii. Results: Five phage clones showed the highest reactivity toward A. baumannii. Among five soluble scFvs, derived from positive phage clones, two scFvs, EB211 and EB279, had high expression yields and displayed strong binding to A. baumannii compared with the controls. Moreover, XDR A. baumannii strains treated with positively-charged scFvs, including EB211, EB279, or a cocktail of EB211 and EB279 (200 µg/ml), displayed lower viability (approximately 50%, 78%, and 40% viability, respectively) compared with PBS-treated bacteria.Conclusion: These results suggest that combining last-resort antibiotics with bactericidal scFvs could provide promising outcomes in immunocompromised individuals with A. baumannii infections.

Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) is a serious global health challenge. It is increasingly associated with nosocomial infections and outbreaks in healthcare facilities. This study was conducted in a tertiary care teaching hospital in Jaipur to quantitate the burden of CRAB in our setup, examine the clinico-epidemiological profile of patients infected with this bug, and determine their antibiotic susceptibility pattern. Methods: Clinical specimens collected from patients admitted in various wards and ICUs were processed. Bacterial identification and susceptibility testing were done using standard laboratory techniques and VITEK 2 automated system. Only one isolate per patient was included for study purposes. The data on the sociodemographic and epidemiological profile was collected and analyzed statistically. Results: A total of 4897 clinical samples were received in the department of microbiology during the study period, out of which 1517 exhibited significant growth, sample positivity rate being 31%. Acinetobacter baumannii was the third most common gram-negative isolate (228/1067; 21.3%). Out of the total 228 A. baumannii isolates, 221 (97%) were carbapenem resistant. The maximum number of CRAB isolates were obtained from endotracheal secretions (103), followed by blood (59). All patients were critically ill and needed intensive care. The antibiotic susceptibility testing of these clinical isolates revealed a high level of resistance (99%) against ceftazidime, meropenem, and imipenem with the least resistance against colistin (2%) and tigecycline (9%). Conclusions: CRAB is an important global pathogen contributing to increased morbidity and mortality in hospitalized patients. Viable treatment options that may be used with success against bugs include minocycline, tigecycline, and polymyxins.

Bacteria express a plethora of efflux pumps that can transport structurally varied molecules, including antimicrobial agents and antibiotics, out of cells. Thus, efflux pump systems participate in lowering intracellular concentrations of antibiotics, which allows phenotypic multidrug-resistant (MDR) bacteria to survive effectively amid higher concentrations of antibiotics. Acinetobacter baumannii is one of the classic examples of pathogens that can carry multiple efflux pump systems, which allows these bacteria to be MDR-to-pan-drug resistant and is now considered a public health threat. Therefore, efflux pumps in A. baumannii have gained major attention worldwide, and there has been increased interest in studying their mechanism of action, substrates, and potential efflux pump inhibitors (EPIs). Efflux pump inhibitors are molecules that can inhibit efflux pumps, rendering pathogens susceptible to antimicrobial agents, and are thus considered potential therapeutic agents for use in conjunction with antibiotics. This review focuses on the types of various efflux pumps detected in A. baumannii, their molecular mechanisms of action, the substrates they transport, and the challenges in developing EPIs that can be clinically useful in reference to A. baumannii.

Nosocomial infections represent one of the biggest health problems nowadays. Acinetobacter baumannii is known as an opportunistic pathogen in humans, affecting people with compromised immune systems, and is becoming increasingly important as a hospital-derived infection. It is known that in recent years, more and more bacteria have become multidrug-resistant (MDR) and, for this reason, the development of new drugs is a priority. However, these products must not affect the human body, and therefore, cytotoxicity studies are mandatory. In this context, antimicrobial peptides with potential antibacterial proprieties could be an alternative. In this research, we describe the synthesis and the bioactivity of dermaseptins and their derivatives against Acinetobacter baumannii. The cytotoxicity of these compounds was investigated on the HEp-2 cell line by MTT cell viability assay. Thereafter, we studied the morphological alterations caused by the action of one of the active peptides on the bacterial membrane using atomic force microscopy (AFM). The cytotoxicity of dermaseptins was concentration-dependent at microgram concentrations. It was observed that all tested analogs exhibited antibacterial activity with Minimum Inhibitory Concentrations (MICs) ranging from 3.125 to 12.5 μg/mL and Minimum Bactericidal Concentrations (MBCs) ranging from 6.25 to 25 μg/mL. Microscopic images obtained by AFM revealed morphological changes on the surface of the treated bacteria caused by K4S4(1-16), as well as significant surface alterations. Overall, these findings demonstrate that dermaseptins might constitute new lead structures for the development of potent antibacterial agents against Acinetobacter baumannii infections.

The interruption of bacteriological surveillance due to the COVID-19 pandemic brought serious consequences, such as the collapse of health systems and the possible increase in antimicrobial resistance. Therefore, it is necessary to know the rate of resistance and its associated mechanisms in bacteria causing hospital infections during the pandemic. The aim of this work was to show the phenotypic and molecular characteristics of antimicrobial resistance in ESKAPE bacteria in a Mexican tertiary care hospital in the second and third years of the pandemic. For this purpose, during 2021 and 2022, two hundred unduplicated strains of the ESKAPE group (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii) were collected from various clinical sources and categorized by resistance according to the CLSI. An analysis of variance (ANOVA) complemented by the Tukey test was performed to search for changes in antimicrobial susceptibility profiles during the study period. Finally, the mechanisms of resistance involved in carbapenem resistance were analyzed, and the search for efflux pumps and high-risk sequence types in A. baumannii was performed by multilocus analysis (MLST). The results showed no changes in K. pneumoniae resistance during the period analyzed. Decreases in quinolone resistance were identified in E. coli (p = 0.039) and P. aeruginosa (p = 0.03). Interestingly, A. baumannii showed increases in resistance to penicillins (p = 0.004), aminoglycosides (p < 0.001, p = 0.027), carbapenems (p = 0.027), and folate inhibitors (p = 0.001). Several genes involved in carbapenem resistance were identified (blaNDM, blaVIM, blaOXA, blaKPC, blaOXA-40, and blaOXA-48) with a predominance of blaOXA-40 and the adeABCRS efflux pump in A. baumannii. Finally, MLST analysis revealed the presence of globally distributed sequence types (ST369 and ST758) related to hospital outbreaks in other parts of the world. The results presented demonstrate that the ESKAPE group has played an important role during the COVID-19 pandemic as nosocomial antibiotic-resistant pathogens and in particular A. baumannii MDR as a potential reservoir of resistance genes. The implications of the increases in antimicrobial resistance in pathogens of the ESKAPE group and mainly in A. baumannii during the COVID-19 pandemic are analyzed and discussed.

This review focuses on Acinetobacter baumannii, a Gram-negative bacterium that causes various infections and whose multidrug resistance has become a significant challenge in clinical practices. There are multiple bacterial mechanisms in A. baumannii that participate in bacterial colonization and immune responses. It is believed that outer membrane vesicles (OMVs) budding from the bacteria play a significant role in mediating bacterial survival and the subsequent attack against the host. Most OMVs originate from the bacterial membranes and molecules are enveloped in them. Elements similar to the pathogen endow OMVs with robust virulence, which provides a new direction for exploring the pathogenicity of A. baumannii and its therapeutic pathways. Although extensive research has been carried out on the feasibility of OMV-based vaccines against pathogens, no study has yet summarized the bioactive elements, biological activity, and vaccine applicability of A. baumannii OMVs. This review summarizes the components, biogenesis, and function of OMVs that contribute to their potential as vaccine candidates and the preparation methods and future directions for their development.

Background The burden of hospital-acquired infections (HAIs) is all assumption based, and the true burden remains unknown in most countries, particularly in the developing countries where healthcare facilities are suboptimal and knowledge is limited. Methodology This cross-sectional study was conducted at the trauma center of a tertiary care institute from August to September 2019, to assess the burden of HAI and antibiotic resistance pattern of HAI. The total sample size in our study was 105. Our objective was to estimate the point prevalence of HAI and study the associated factors in a tertiary care hospital. Result In this study, the point prevalence of HAI was five to six times higher when compared with that of developed countries. Gram-negative organisms were the predominant bacteria; with Acinetobacter baumannii the most common among them. Conclusion Point-prevalence survey is an important objective of the antimicrobial stewardship program; it will be helpful in controlling antimicrobial resistance and this tool plays a significant role in hospital settings. Our study is quite pertinent to assess the point prevalence of HAI. It will help in knowing the current prevalence and pattern of the HAI. Therefore, as healthcare administrators, we can further decrease the HAI for better patient outcomes in the future.

Extensively drug-resistant Acinetobacter baumannii is considered one of the most dangerous threats to global health, requiring novel therapeutic interventions. The outer membrane protein A (OmpA) is an immunogenic agent that triggers immune responses. The current study evaluated serum antibody levels against previously determined immunogenic OmpA peptides from A baumannii in ICU staff. Serum samples were collected from 62 ICU staff members (representing the exposed group), healthy controls (representing the nonexposed group), and patients with systemic lupus erythematosus (SLE) (as controls for nonspecific antibody reactions). After excluding the cross-reactive antibodies via Escherichia coli lysate pretreatment, all the samples were assessed in the vicinity of A baumannii lysate by enzyme-linked immunosorbent assay (ELISA). All the positive samples were assessed for interaction with previously designed and selected peptides using ELISA. The protective potential of positive serum antibodies was surveyed in vitro using an opsonophagocytic study. The most antibody positive samples against one of the dominant peptides were determined in the ICU personnel (75%). SLE serum samples did not react with candidate peptides. The strongest positive reaction was observed in serum treatment with one of the OmpA peptides (No. 5) with significant differences compared to other designed peptides. Our findings showed that ICU samples have substantially higher antibody levels than the nonexposed group; Positive samples show strong results in the opsonophagocytosiis assay. This study demonstrates A baumannii colonization at human mucosal surfaces, especially in exposed healthy workers. Novel OmpA-derived peptides could be used to identify immunogenic vaccine candidates. Therefore, more studies are needed before this peptide and antibody levels are used in diagnosis, prevention, or treatment.

Acinetobacter baumannii is an opportunistic pathogen that has recently emerged as a global threat associated with high morbidity, mortality, and antibiotic resistance. We determined the role of type I interferon (IFN) signaling in A. baumannii infection. We report that A. baumannii can induce a type I IFN response that is dependent upon TLR4-TRIF-IRF3 and phagocytosis of the bacterium. Phase variants of A. baumannii that have a reduced capsule, lead to enhanced TLR4-dependent type I IFN induction. This was also observed in a capsule-deficient strain. However, we did not observe a role for this pathway in vivo. The enhanced signaling could be accounted for by increased phagocytosis in capsule-deficient strains that also lead to enhanced host cell-mediated killing. The increased cytokine response in the absence of the capsule was not exclusive to type I IFN signaling. Several cytokines, including the proinflammatory IL-6, were increased in cells stimulated with the capsule-deficient strain, also observed in vivo. After 4 h in our acute pneumonia model, the burden of a capsule-null strain was significantly reduced, yet we observed increases in innate immune cells and inflammatory markers compared to wild-type A. baumannii. This study underscores the role of phase variation in the modulation of host immune responses and indicates that the capsule of A. baumannii plays an important role in protection against host cell killing and evasion from activation of the innate immune response.