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The occurrence and transmission of carbapenemase-producing-Enterobacterales (CPE) on a global scale has become a major issue. Clinical reports are rarely providing information on the genomic and plasmid features of carbapenem-resistant Serratia marcescens . Our objective was to investigate the resistance and transmission dynamics of two carbapenem-resistant S. marcescens that are resistant to carbapenem and have caused bacteremia in China. Blood specimens were taken from two individuals with bacteremia. Multiplex PCR was employed to identify genes that code for carbapenemase. Antimicrobial susceptibility tests and plasmid analysis were conducted on S. marcescens isolates SM768 and SM4145. The genome of SM768 and SM4145 were completely sequenced using NovaSeq 6000-PE150 and PacBio RS II platforms. Antimicrobial resistance genes (ARGs) were predicted using the ResFinder tool. S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and southern blotting were employed to analyze plasmids. Two S. marcescens that produced KPC-2 were identified from bloodstream infections. The antimicrobial susceptibility testing demonstrated that both of the isolates had a resistance to various antibiotics. The whole-genome sequence (WGS) and plasmid analysis revealed the presence of bla KPC-2 -bearing IncR plasmids and multiple plasmid-borne antimicrobial resistance genes in the isolates. Our comparative plasmid analysis suggested that the two IncR plasmids identified in this study could be derived from a common ancestor. Our findings revealed the emergence of bla KPC-2 -bearing IncR plasmid in China, which could be a hindrance to the transmission of KPC-2-producing S. marcescens in clinical settings., Competing Interests: The authors declare that the research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Jia, Huang, Zhang, Sheng, Chu, Xu and Xu.)

Drug-resistant bacterial infections have caused serious threats to human health and call for effective antibacterial agents that have low propensity to induce antimicrobial resistance. Host defense peptide-mimicking peptides are actively explored, among which poly-β-l-lysine displays potent antibacterial activity but high cytotoxicity due to the helical structure and strong membrane disruption effect. Here, we report an effective strategy to optimize antimicrobial peptides by switching membrane disrupting to membrane penetrating and intracellular targeting by breaking the helical structure using racemic residues. Introducing β-homo-glycine into poly-β-lysine effectively reduces the toxicity of resulting poly-β-peptides and affords the optimal poly-β-peptide, βLys 50 HG 50 , which shows potent antibacterial activity against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) and MRSA persister cells, excellent biosafety, no antimicrobial resistance, and strong therapeutic potential in both local and systemic MRSA infections. The optimal poly-β-peptide demonstrates strong therapeutic potential and implies the success of our approach as a generalizable strategy in designing promising antibacterial polypeptides.

Secondary metabolites profoundly affect microbial physiology, metabolism and stress responses. Increasing evidence suggests that these molecules can modulate microbial susceptibility to commonly used antibiotics; however, secondary metabolites are typically excluded from standard antimicrobial susceptibility assays. This may in part account for why infections by diverse opportunistic bacteria that produce secondary metabolites often exhibit discrepancies between clinical antimicrobial susceptibility testing results and clinical treatment outcomes. In this Review, we explore which types of secondary metabolite alter antimicrobial susceptibility, as well as how and why this phenomenon occurs. We discuss examples of molecules that opportunistic and enteric pathogens either generate themselves or are exposed to from their neighbours, and the nuanced impacts these molecules can have on tolerance and resistance to certain antibiotics., (© 2021. Springer Nature Limited.)

Gram-negative bacteria pose a serious public health concern due to resistance to many antibiotics, caused by the low permeability of their outer membrane (OM). Effective antibiotics use porins in the OM to reach the interior of the cell; thus, understanding permeation properties of OM porins is instrumental to rationally develop broad-spectrum antibiotics. A functionally important feature of OM porins is undergoing open-closed transitions that modulate their transport properties. To characterize the molecular basis of these transitions, we performed an extensive set of molecular dynamics (MD) simulations of Escherichia coli OM porin OmpF. Markov-state analysis revealed that large-scale motion of an internal loop, L3, underlies the transition between energetically stable open and closed states. The conformation of L3 is controlled by H bonds between highly conserved acidic residues on the loop and basic residues on the OmpF β -barrel. Mutation of key residues important for the loop's conformation shifts the equilibrium between open and closed states and regulates translocation of permeants (ions and antibiotics), as observed in the simulations and validated by our whole-cell accumulation assay. Notably, one mutant system G119D, which we find to favor the closed state, has been reported in clinically resistant bacterial strains. Overall, our accumulated ∼200 µs of simulation data (the wild type and mutants) along with experimental assays suggest the involvement of internal loop dynamics in permeability of OM porins and antibiotic resistance in Gram-negative bacteria., Competing Interests: The authors declare no competing interest.

Bacteria have membrane-spanning efflux pumps to secrete toxic compounds ranging from heavy metal ions to organic chemicals, including antibiotic drugs. The overall architecture of these efflux pumps is highly conserved: with an inner membrane energy-transducing subunit coupled via an adaptor protein to an outer membrane conduit subunit that enables toxic compounds to be expelled into the environment. Here, we map the distribution of efflux pumps across bacterial lineages to show these proteins are more widespread than previously recognised. Complex phylogenetics support the concept that gene cassettes encoding the subunits for these pumps are commonly acquired by horizontal gene transfer. Using TolC as a model protein, we demonstrate that assembly of conduit subunits into the outer membrane uses the chaperone TAM to physically organise the membrane-embedded staves of the conduit subunit of the efflux pump. The characteristics of this assembly pathway have impact for the acquisition of efflux pumps across bacterial species and for the development of new antimicrobial compounds that inhibit efflux pump function., Competing Interests: The authors have declared that no competing interests exist.

Objective: This study aimed to demonstrate the importance of active carbapenem-resistant Enterobacterales (CRE) surveillance and evaluate the prevalence of invasive infections, risk factors, and mortality risk in CRE-colonized patients., Methods: Retrospective cohort study analyzing 1,920 patients identified using an active CRE surveillance protocol, admitted to an adult intensive care unit in southeastern Brazil from January 2014 to December 2018., Results: There were 297 (15.47%) CRE colonized patients, with one colonized for every six control patients. CRE-colonized patients demonstrated an increased chance of infection (odds ratio [OR] 7.967, p < 0.001). Overall, 20.54% of the colonized patients presented invasive infection (81.96% due to Klebsiella pneumoniae). The colonization and infection ratio demonstrated the important role of the active CRE surveillance protocol. There were identified multiple risk factors for CRE colonization, including long-term mechanical ventilation (OR 1.624, p = 0.019) and previous exposure to aminopenicillins (OR 5.204, p < 0.001), carbapenems (OR 3.703, p = 0.017), cephalosporins (OR 12.036, p < 0.001), and fluoroquinolones (OR 5.238, p = 0.012). The mortality risk was significantly higher among colonized (OR 2.356, p < 0.001) and colonized-infected (OR 2.000, p = 0.009) patients and in those with Enterobacter cloacae colonization (OR 5.173, p < 0,001) and previous aminopenicillins exposure (OR 3.452, p = 0.007)., Conclusions: Early detection of CRE colonization through screening testing proved to be an important tool to control CRE spread. However, observation over the years has shown no effective control of colonization and infection. The prevalence rates of CRE colonization and colonization-infection were high, as were the mortality rates. In conclusion, an active CRE surveillance protocol is essential, but its impact depends on the effective implementation of preventive measures and feedback between team members., Competing Interests: The authors have declared that no competing interests exist.

Background: The objectives of this study were; (I) to determine the proportion of pathogens isolated from patients with infected chronic wounds in the surgical ward of MRRH that are resistant to the third-generation cephalosporins and (II) to determine the factors associated with resistance to third-generation cephalosporins in the surgical ward of MRRH., Method(s): This study was a descriptive analytical survey of bacterial isolates from infected chronic wounds among patients admitted in the surgical ward of MRRH, Uganda. Seventy five (75) study participants were recruited in the study using convenient sampling technique. Bacterial culture and identification was performed using standard microbiology laboratory procedures whereas broth microdilution method was used to establish the susceptibility of the identified pathogens. Data for objective one (1) was summarized as proportions while the categorized variables were analyzed using logistic regression to determine whether they were associated with the resistance patterns. The level of significance was preset at 5% and p-values less than 0.05 were considered statistically significant., Results: Generally, all isolates had complete susceptibility (100%) to Cefoperazone+Sulbactam 2g except 7.1% of proteus spp that were resistant. Of all the bacterial isolates studied, Staphylococcus aureus, Enterobacter agglomerans, providencia spp and pseudomonas earuginosa had complete resistance (100%) to Cefopodoxime 200mg while providencia spp and pseudomomas earuginosa had complete resistance (100%) to Cefixime 400mg and cefotaxime 1g. Finally, higher odds of bacterial resistance to more 2 brands of the third generation cephalosporins were observed among participants who had prior exposure to the third generation cephalosporins (OR, 2.22, 95% CI, 0.80-6.14), comorbidities (OR, 1.76, 95% CI, 0.62-4.96) and those who had more than two hospitalizations in a year (OR, 1.39, 95% CI 0.46-4.25). However, multivariate logistic regression was not performed since no factor was significantly associated with resistance to more than two brands of third generation cephalosporins (p >0.05)., Conclusion: This study found that cefixime and cefpodoixme had high rates of resistance and should not be used in routine management of infected chronic wounds. In addition, the factors investigated in this study were not significantly associated with bacterial resistance to more than two brands of third generation cephalosporins., Competing Interests: The authors have declared that no competing interests exist.

Since the discovery of the first MDM2 inhibitors, we have gained deeper insights into the cellular roles of MDM2 and p53. In this review, we focus on MDM2 inhibitors that bind to the p53-binding domain of MDM2 and aim to disrupt the binding of MDM2 to p53. We describe the basic mechanism of action of these MDM2 inhibitors, such as nutlin-3a, summarise the determinants of sensitivity to MDM2 inhibition from p53-dependent and p53-independent points of view and discuss the problems with innate and acquired resistance to MDM2 inhibition. Despite progress in MDM2 inhibitor design and ongoing clinical trials, their broad use in cancer treatment is not fulfilling expectations in heterogenous human cancers. We assess the MDM2 inhibitor types in clinical trials and provide an overview of possible sources of resistance to MDM2 inhibition, underlining the need for patient stratification based on these aspects to gain better clinical responses, including the use of combination therapies for personalised medicine., (© 2021. The Author(s).)

Improving prudent use of antibiotics is one way to limit the spread of antimicrobial resistance (AMR). The objective of this systematic review was to assess the effects of financial strategies targeting healthcare providers on the prudent use of antibiotics. A systematic review of the literature was conducted searching PubMed, Embase and Cochrane databases, and the grey literature. Search terms related to antibacterial agents, drug resistance, financial strategies, and healthcare providers and/or prescribers. Twenty-two articles were included in the review, reporting on capitation and salary reimbursement, cost containment interventions, pay-for-performance initiatives, penalties, and a one-off bonus payment. There was substantial variation in the reported outcomes describing prescribing behaviours, including proportion of patients prescribed antibiotics, antibiotic prescriptions per patient, and number of cases treated with recommended antibiotic therapy. All financial strategies were associated with improvements in the appropriate prescription of antibiotics in the short-term, although the magnitude of observed effects varied across financial strategies. Financial penalties were associated with the greatest decreases in inappropriate antibiotic prescriptions, followed by capitation models and pay-for-performance schemes that paid bonuses upon achievement of performance targets. However, the risk of bias across studies must be noted. Findings point to the viability of financial strategies to promote the prudent use of antibiotics. Measuring the downstream impact of prescriber behaviour changes is key to estimating the true value of such interventions to tackle AMR. Research efforts should continue to build the evidence on causal mechanisms driving provider prescribing patterns for antibiotics and the long-term impact on antibiotic prescriptions., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The emerging discipline of Quantitative Systems Pharmacology (QSP) enables the integration of quantitative experimental data describing the interactions between the various biological processes within the system using mathematical modeling to gain better insights into the factors that drive disease pathogenicity and influence antibiotic pharmacokinetics (PKs)/pharmacodynamics (PDs). Through our perspective we consider the evolution from PK/PD models to mechanism-based and systems-based models and then finally QSP. We further emphasize the need to invest in ambitious research that takes into consideration: (i) the antibiotic PK/PD activity, (ii) the time course of the host immune response to understand the progression of the infection, (iii) and a growing appreciation of the cellular and molecular networks using multi-omics analysis to understand the modulation of antimicrobial therapy at a true systems level., (© 2021 The Authors Clinical Pharmacology & Therapeutics © 2021 American Society for Clinical Pharmacology and Therapeutics.)

The post-antibiotic effect (PAE) of ceftazidime-avibactam in vivo was evaluated using models of thigh- and lung-infection with Pseudomonas aeruginosa in neutropenic mice. In thigh-infected mice, the PAE was negative (-2.18 to -0.11 h) for three of four strains: caused by a 'burst' of rapid bacterial growth after the drug concentrations had fallen below their pre-specified target values. With lung infection, PAE was positive, and longer for target drug concentrations in ELF (>2 h) than plasma (1.69-1.88 h). The time to the start of regrowth was quantified as a new parameter, PAE R , which was positive (0.35-1.00 h) in both thigh- and lung-infected mice. In the context that measurements of the PAE of β-lactam/β-lactamase inhibitor combinations in vivo have not previously been reported, it is noted that the negative values were consistent with previous measurements of the PAE of ceftazidime-avibactam in vitro and of ceftazidime alone in vivo .

Monensin is an ionophore for monovalent cations, which is frequently used to prevent ketosis and to enhance performance in dairy cows. Studies have shown the rumen bacteria Prevotella bryantii B 1 4 being less affected by monensin. The present study aimed to reveal more information about the respective molecular mechanisms in P. bryantii , as there is still a lack of knowledge about defense mechanisms against monensin. Cell growth experiments applying increasing concentrations of monensin and incubations up to 72 h were done. Harvested cells were used for label-free quantitative proteomics, enzyme activity measurements, quantification of intracellular sodium and extracellular glucose concentrations and fluorescence microscopy. Our findings confirmed an active cell growth and fermentation activity of P. bryantii B 1 4 despite monensin concentrations up to 60 µM. An elevated abundance and activity of the Na + -translocating NADH:quinone oxidoreductase counteracted sodium influx caused by monensin. Cell membranes and extracellular polysaccharides were highly influenced by monensin indicated by a reduced number of outer membrane proteins, an increased number of certain glucoside hydrolases and an elevated concentration of extracellular glucose. Thus, a reconstruction of extracellular polysaccharides in P. bryantii in response to monensin is proposed, which is expected to have a negative impact on the substrate binding capacities of this rumen bacterium.

Bacterial infections are predominantly treated with antibiotics, and resistance to antibiotics is becoming an increasing threat to our health. Pore-forming toxins (PFTs) are virulence factors secreted by many pathogenic bacterial strains, both in acute and chronic infections. They are special membrane-targeting proteins that exert toxic effects by forming pores in the cell membrane. Recent studies have elucidated the structure of PFTs and the detailed molecular mechanisms of their pathogenicity. Here, we discuss recent findings that highlight the regulatory mechanisms and important roles of two types of PFTs, α-PFTs and β-PFTs, in mediating the virulence of bacteria, and the therapeutic potential of targeting PFTs for antibacterial treatment. Therapeutic strategies based on PFTs are highly specific and may alleviate the issue of increasing resistance to antibiotics., 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., (© 2021 Hu et al.)

Intravenous cefiderocol (Fetroja ® ; Fetcroja ® ) is the first siderophore cephalosporin approved for the treatment of adults with serious Gram-negative bacterial infections. Cefiderocol is stable against all four Ambler classes of β-lactamases (including metallo-β-lactamases) and exhibits excellent in vitro activity against many clinically relevant Gram-negative pathogens, including multidrug resistant strains. In randomized, double-blind clinical trials, cefiderocol was noninferior to imipenem/cilastatin for the treatment of complicated urinary tract infections (cUTI) and to meropenem for nosocomial pneumonia. Furthermore, in a pathogen-focused clinical trial in patients with carbapenem-resistant (CR) infections, cefiderocol showed comparable efficacy to best available therapy (BAT), albeit all-cause mortality rate was higher in the cefiderocol arm, the cause of which has not been established. Cefiderocol had a good tolerability and safety profile in clinical trials. Thus cefiderocol is a novel, emerging, useful addition to the current treatment options for adults with susceptible Gram-negative bacterial infections (including cUTI and nosocomial pneumonia) for whom there are limited treatment options., (© 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The immune system is a dynamic network of cells and cytokines are the major mediators of immune responses which combat pathogens. Based on the cytokine production, effector T cells differentiate into subsets known as Th1, Th2, Th17, or Treg. This system serves as a barrier to intracellular pathogens, bacterial infections and stimulates the production of reactive oxygen species (ROS), reactive nitrogen intermediates, and nitric oxide, which diffuses across membranes and engulfs intracellular pathogens. Oxidative stress occurs when ROS, reactive nitrogen species (RNS) production, and antioxidant defences become imbalanced. Oxidative stress generated by infected cells produces a substantial amount of free radicals which enables the killing of intracellular pathogens. Intracellular pathogens are exposed to endogenous ROS as part of normal aerobic respiration, also exogenous ROS and RNS are generated by the host immune system in response to infection. Nanoparticles which are designed for drug delivery are capable of trapping the desired drug in the particles which protect the drug from enzymatic degradation in a biological system. The subcellular size of nanoparticles enables higher intracellular uptake of the drug which results in the reduction of the concentration of free drugs reducing their toxic effect. Research on the modulation of immune response and oxidative stress using nanoparticles used to encapsulate drugs has yet to be explored fully. In this review, we illustrate the immune activation and generation of oxidative stress properties which are mediated by nanoparticle encapsulated drug delivery systems which can make the therapy more effective in case of diseases caused by intracellular pathogens., (Copyright © 2021 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Antimicrobial resistance (AMR) developed by Salmonella within animals used for food products is a major global issue. Monitoring AMR in animals destined for slaughter is, therefore, critical. Abattoirs may serve as potential candidate checkpoints for monitoring resistance patterns on farms. A complicating factor, however, is the impact of lairage on Salmonella detected in pigs at slaughter. This study sought to compare AMR patterns in Salmonella spp. in swine collected upon arrival (fecal samples) at the abattoir with those at postslaughter (cecal samples) and evaluate the feasibility of using slaughterhouse samples for surveillance of prevailing AMR Salmonella on farms. Eighty-four Salmonella isolates were recovered from a large, midwestern U.S. abattoir between September and November 2013. Isolates were tested for phenotypic AMR to 12 antimicrobials using the broth microdilution assay. Whole-genome sequencing identified the AMR genes harbored by the strains. Significant differences were observed in the isolate phenotypes and genotypes; however, no significant difference was observed in genotypic resistance patterns. Hence, the AMR profiles of Salmonella spp. postslaughter cannot be predicted from preslaughter samples. Further research considering the genetic diversity of isolates and statistical power of the genotypic analysis is warranted to improve the performance of WGS-inferred antimicrobial susceptibility.

In this study, lead (Pb) biosorption studies in aqueous solution were performed with metal-resistant Bacillus strain MRS-2 (ATCC 55674) bacterium which was previously isolated from wastewater plant. It showed minimum inhibition concentration of 300 ppm Pb on the nutrient agar plates. Pb biosorption using MRS-2 bacteria was investigated under different parameters such as pH, temperature, biomass dosage, initial Pb concentration, contact time, and type of biomass by batch experiments. Pb concentration was analyzed through Inductively coupled plasma-optical emission spectrometry. The rate of biosorption (Q) and Pb biosorption capacity (q e ) were calculated for above mentioned parameters. It was observed that Pb precipitates by itself from the solution at pH 2 and 8 or above without bacteria and precipitation did not increase even in the presence of bacteria. The results showed that the highest biosorption rate and biosorption capacity (mg/g) were observed at pH 7, 25°C, 2-h contact time with live bacteria. The highest biosorption rate was observed at 1.5 g/L biomass dose and 5 ppm initial Pb concentration, whereas the highest Pb biosorption capacity was observed at 0.25 g/L biomass dose and 12.5 ppm initial Pb concentration. It was observed that Pb biosorption by live bacteria occurred through adsorption on cell surface. In this study, the biosorption isotherm analysis favored the Langmuir isotherm model indicating monolayer biosorption. This Bacillus strain showed higher Pb biosorption capacity than most of the previously reported Bacillus strains. In conclusion, this study indicates that the Bacillus MRS-2 strain can be used to remove Pb from industrial wastewaters in an ecofriendly approach., (© 2021 Wiley-VCH GmbH.)

Pseudomonas aeruginosa is an opportunistic pathogen that uses malonate among its many carbon sources. We recently reported that, when grown in blood from trauma patients, P. aeruginosa expression of malonate utilization genes was upregulated. In this study, we explored the role of malonate utilization and its contribution to P. aeruginosa virulence. We grew P. aeruginosa strain PA14 in M9 minimal medium containing malonate (MM9) or glycerol (GM9) as a sole carbon source and assessed the effect of the growth on quorum sensing, virulence factors, and antibiotic resistance. Growth of PA14 in MM9, compared to GM9, reduced the production of elastases, rhamnolipids, and pyoverdine; enhanced the production of pyocyanin and catalase; and increased its sensitivity to norfloxacin. Growth in MM9 decreased extracellular levels of N-acylhomoserine lactone autoinducers, an effect likely associated with increased pH of the culture medium; but had little effect on extracellular levels of PQS. At 18 hr of growth in MM9, PA14 formed biofilm-like structures or aggregates that were associated with biomineralization, which was related to increased pH of the culture medium. These results suggest that malonate significantly impacts P. aeruginosa pathogenesis by influencing the quorum sensing systems, the production of virulence factors, biofilm formation, and antibiotic resistance., (© 2021 John Wiley & Sons Ltd.)

Salmonella enterica is a foodborne pathogen of global public health importance with developing countries mostly affected. Foodborne outbreaks are often attributed to pork consumption and Salmonella contamination of retail pork is directly linked to the Salmonella prevalence on farm. The widespread use of antimicrobials at different steps of swine production can favor resistant strains of Salmonella. The objectives of this study are to characterize the distribution, multilocus sequence typing (MLST), plasmid, virulence profiles and antimicrobial resistance of Salmonella serovars circulating in selected pig farms. Six hundred fecal samples were randomly collected from nine selected farms in Ilorin, Nigeria. Isolates were analyzed by cultural isolation using selective media, conventional biochemical characterization, serotyping, MLST and whole genome sequencing (WGS). Sixteen samples were positive for Salmonella sub-species, comprising of nine serovars. The antimicrobial susceptibility results revealed low-level resistance against 13 antimicrobial agents. Five strains exhibited resistance to nalidixic acid and intermediate resistance to ciprofloxacin with chromosomal (double) mutation at gyrA and parC while four strains possessed single mutation in parC. Salmonella Kentucky showed double mutation each at gyrA and parC. WGS analysis, revealed eight diverse sequence types (STs), the most common STs were ST-321 and ST-19 (n = 4) exhibited by S. Muenster and S. Typhimurium, respectively. Single Nucleotide Polymorphism (SNP)-based phylogeny analysis showed the 16 isolates to be highly related and fell into 8 existing clusters at NCBI Pathogen Detection. Curtailing the spread of resistant strains will require the establishment of continuous surveillance program at the state and national levels in Nigeria. This study provides useful information for further studies on antimicrobial resistance mechanisms in foodborne Salmonella species., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This study evaluates the electrical potential and chemical alterations in laboratory-induced colistin-resistant Klebsiella pneumoniae , as compared to the susceptible strain using spectroscopic analyses. The minimal inhibitory concentration (MIC) of colistin, ζ-potential and chemical composition analysis of K. pneumoniae strains are determined. The results obtained for the K. pneumoniae Col-R with induced high-level colistin resistance (MIC = 16.0 ± 0.0 mg/L) are compared with the K. pneumoniae Col-S strain susceptible to colistin (MIC = 0.25 ± 0.0 mg/L). Fourier transform infrared (FTIR) and Raman spectroscopic studies revealed differences in bacterial cell wall structures and lipopolysaccharide (LPS) of K. pneumoniae Col-R and K. pneumoniae Col-S strains. In the beginning, we assumed that the obtained results could relate to a negative charge of the bacterial surface and different electrostatic interactions with cationic antibiotic molecules, reducing the affinity of colistin and leading to its lower penetration into K. pneumoniae Col-R cell. However, no significant differences in the ζ-potential between the K. pneumoniae Col-R and K. pneumoniae Col-S strains are noticed. In conclusion, this mechanism is most probably associated with recognisable changes in the chemical composition of the K. pneumoniae Col-R cell wall (especially in LPS) when compared to the susceptible strain.

Lactic Acid Bacteria (LAB) regulate and maintain the stability of healthy microbial flora, inhibit the adhesion of pathogenic bacteria and promote the colonization of beneficial micro-organisms. The drug resistance and pathogenicity of Salmonella enteritis SE47 isolated from retail eggs were investigated. Meanwhile, Enterococcus faecalis L76 and Lactobacillus salivarius LAB35 were isolated from intestine of chicken. With SE47 as indicator bacteria, the diameters of L76 and LAB35 inhibition zones were 12 mm and 8·5 mm, respectively, by agar inhibition circle method, which indicated that both of them had inhibitory effect on Salmonella, and L76 had better antibacterial effect; two chicken-derived lactic acid bacteria isolates and Salmonella SE47 were incubated with Caco-2. The adhesion index of L76 was 17·5%, which was much higher than that of LAB35 (10·21%) and SE47 (4·89%), this experiment shows that the higher the bacteriostatic effect of potential probiotics, the stronger the adhesion ability; then Caco-2 cells were incubated with different bacteria, and the survival of Caco-2 cells was observed by flow cytometry. Compared with Salmonella SE47, the results showed that lactic acid bacteria isolates could effectively protect Caco-2 cells; finally, after different bacteria incubated Caco-2 cells, according to the cytokine detection kit, the RNA of Caco-2 cells was extracted and transcribed into cDNA, then detected by fluorescence quantitative PCR, the results showed that L76 could protect Caco-2 cells from the invasion of Salmonella SE47, with less cell membrane rupture and lower expression of MIF and TNF genes. Therefore, the lactic acid bacteria isolates can effectively inhibit the adhesion of Salmonella and protect the integrity of intestinal barrier., (© 2021 The Society for Applied Microbiology.)

Bacterial antibiotic persistence occurs when bacteria are treated with an antibiotic and the majority of the population rapidly dies off, but a small subpopulation enters into a dormant, persistent state and evades death. Diverse pathways leading to nucleoside triphosphate (NTP) depletion and restricted translation have been implicated in persistence, suggesting alternative redundant routes may exist to initiate persister formation. To investigate the molecular mechanism of one such pathway, functional variants of an essential component of translation (phenylalanyl-tRNA synthetase [PheRS]) were used to study the effects of quality control on antibiotic persistence. Upon amino acid limitation, elevated PheRS quality control led to significant decreases in aminoacylated tRNA Phe accumulation and increased antibiotic persistence. This increase in antibiotic persistence was most pronounced (65-fold higher) when the relA- encoded tRNA-dependent stringent response was inactivated. The increase in persistence with elevated quality control correlated with ∼2-fold increases in the levels of the RNase MazF and the NTPase MazG and a 3-fold reduction in cellular NTP pools. These data reveal a mechanism for persister formation independent of the stringent response where reduced translation capacity, as indicated by reduced levels of aminoacylated tRNA, is accompanied by active reduction of cellular NTP pools which in turn triggers antibiotic persistence. IMPORTANCE Bacterial antibiotic persistence is a transient physiological state wherein cells become dormant and thereby evade being killed by antibiotics. Once the antibiotic is removed, bacterial persisters are able to resuscitate and repopulate. It is thought that antibiotic bacterial persisters may cause reoccurring infections in the clinical setting. The molecular triggers and pathways that cause bacteria to enter into the persister state are not fully understood. Our results suggest that accumulation of deacylated tRNA is a trigger for antibiotic persistence independent of the RelA-dependent stringent response, a pathway thought to be required for persistence in many organisms. Overall, this provides a mechanism where changes in translation quality control in response to physiological cues can directly modulate bacterial persistence.

Colistin resistance is complex and multifactorial. DbcA is an inner membrane protein belonging to the DedA superfamily required for maintaining extreme colistin resistance of Burkholderia thailandensis. The molecular mechanisms behind this remain unclear. Here, we report that ∆dbcA displays alkaline pH/bicarbonate sensitivity and propose a role of DbcA in extreme colistin resistance of B. thailandensis by maintaining cytoplasmic pH homeostasis. We found that alkaline pH or presence of sodium bicarbonate displays a synergistic effect with colistin against not only extremely colistin resistant species like B. thailandensis and Serratia marcescens, but also a majority of Gram-negative and Gram-positive bacteria tested, suggesting a link between cytoplasmic pH homeostasis and colistin resistance across species. We found that lowering the level of oxygen in the growth media or supplementation of fermentable sugars such as glucose not only alleviated alkaline pH stress, but also increased colistin resistance in most bacteria tested, likely by avoiding cytoplasmic alkalinization. Our observations suggest a previously unreported link between pH, oxygen, and colistin resistance. We propose that maintaining optimal cytoplasmic pH is required for colistin resistance in a majority of bacterial species, consistent with the emerging link between cytoplasmic pH homeostasis and antibiotic resistance.

The rise of antimicrobial resistance to antibiotics (AMR) as a healthcare crisis has led to a tremendous social and economic impact, whose damage poses a significant threat to future generations. Current treatments either are less effective or result in further acquired resistance. At the same time, several new antimicrobial discovery approaches are expensive, slow, and relatively poorly equipped for translation into the clinical world. Therefore, the use of nanomaterials is presented as a suitable solution. In particular, this review discusses selenium nanoparticles (SeNPs) as one of the most promising therapeutic agents based in the nanoscale to treat infections effectively. This work summarizes the latest advances in the synthesis of SeNPs and their progress as antimicrobial agents using traditional and biogenic approaches. While physiochemical methods produce consistent nanostructures, along with shortened processing procedures and potential for functionalization of designs, green or biogenic synthesis represents a quick, inexpensive, efficient, and eco-friendly approach with more promise for tunability and versatility. In the end, the clinical translation of SeNPs faces various obstacles, including uncertain in vivo safety profiles and mechanisms of action and unclear regulatory frameworks. Nonetheless, the promise possessed by these metalloid nanostructures, along with other nanoparticles in treating bacterial infections and slowing down the AMR crisis, are worth exploring.

The aim of this study was to determine the chemical profile of the essential oils (EOs) of three Moroccan lavender species (Lavandula pedunculata, LP; Lavandula angustifolia, LA; and Lavandula maroccana, LM) and to investigate, for the first time, the synergistic effect of the optimal mixture of the EOs with conventional antibiotic ciprofloxacin against three pathogenic foodborne bacteria. Gas chromatography/mass spectrometry analysis showed that eucalyptol (39·05%), camphor (24·21%) and borneol (8·29%) were the dominant compounds of LA-EO. LP-EO was characterized by the abundance of camphor (74·51%) and fenchone (27·06%), whereas carvacrol (42·08%), camphor (17·95%) and fenchone (12·05%) were the main constituents of LM-EO. EOs alone or combined showed a remarkable antimicrobial activity against the tested bacteria with minimum inhibitory concentrations (MICs) ranging from 3·53 to 15·96 mg ml -1 . The optimal mixture, calculated using a mixture design, corresponded to 19% LA, 38% LP and 43% LM. All combination of the EOs and the best EO mixture with ciprofloxacin exhibited a total synergism with fractional inhibitory concentration index values ranging from 0·27 to 0·37. The best EO mixture showed the highest gain of 128-fold, especially against Salmonella spp., more than that found testing the EOs separately. These findings should be taken into consideration for a possible application in the pharmaceutical and food industries., (© 2021 The Society for Applied Microbiology.)

Biofilm formation is a central feature to guarantee staphylococcal persistence in hosts and is associated with several diseases that are difficult to treat. In this research paper, biofilm formation and antimicrobial susceptibility were investigated in staphylococcal strains belonging to several species. These strains were isolated from the milk of cows with subclinical mastitis and most of them were coagulase-negative, with the prevalence of Staphylococcus chromogenes. High genetic diversity was observed among the strains by pulsed field gel electrophoresis. Antimicrobial resistance was assessed by disk diffusion and more than 50% of the strains were resistant to ampicillin and penicillin G, with multi-resistance profiles (13.6%) also being observed. Most strains (65.9%) formed biofilms when cultivated in BHI supplemented with 1% glucose. Most strains (72.7%) carried the intercellular adhesion gene (icaA), while less than half (36.3%) carried the biofilm-associated protein gene (bap). Concentrations of up to 10xMIC of erythromycin and tetracycline were not sufficient to suppress cell viability in preformed biofilms. Our results revealed that a genetically diverse group of biofilm-forming Staphylococcus species can be involved in subclinical mastitis. Since high antimicrobial concentrations cannot eradicate biofilm cells in vitro, their use in dairy animals may be ineffective in controlling infections, while supporting selection of resistant microorganisms. These data reinforce the need for alternative therapies aiming at disrupting biofilms for effective disease control.

Background: P. aeruginosa is the primary source of hospital-acquired infections. Unfortunately, antibiotic resistance is growing to precariously high levels, making the infections by this pathogen life-threatening and hard to cure. One possible alternative to antibiotics is to use phages. However, the isolation of phages suitable for phage therapy- be lytic, be efficient, and have a broad host range -against some target bacteria has proven difficult. To identify the best places to look for these phages against P. aeruginosa we screened hospital sewages, soils, and rivers in two cities., Results: We isolated eighteen different phages, determined their host range, infection property, and plaque morphology. We found that the sewage and sewage-contaminated environments are the most reliable sources for the isolation of Pseudomonas phages. In addition, phages isolated from hospital sewage showed the highest efficiency in lysing the bacteria used for host range determination. In contrast, phages from the river had larger plaque size and lysed bacteria with higher levels of antibiotic resistance., Conclusions: Our findings provided additional support for the importance of sewage as the source of phage isolation.

The emergence and reemergence of multidrug-resistant (MDR) bacteria and mycobacteria in community and hospital periphery have directly enhanced the hospitalization costs, morbidity and mortality, globally. The appearance of MDR pathogens, the currently used antibiotics, remains insufficient, and the development of potent antibacterial(s) is merely slow. Thus, the development of active antibacterials is the call of the day. The sulfonamides class of antibacterials was the most successful synthesized drug in the 19th century. Mechanically, sulfonamides were targeting bacterial folic acid biosynthesis and today, those are obsolete or clinically inactive. Nevertheless, the magic sulfonamide pharmacophore has been used continuously in several mainstream antibacterial, antidiabetic, antiviral drugs. Concomitantly, thousands of phytochemicals with antimicrobial potencies have been recorded and were commanded as alternate antibacterials toward control of MDR pathogens. However, none/very few isolated phytochemicals have gone up to the pure-drug stage due to the lack of the desired drug-likeness values and the required pharmacokinetic properties. Thus, chemical modification of parent drug remains as the versatile approach in antibacterial drug development. Improvement of clinically inactive sulfa drugs with suitable phytochemicals to develop active, low-toxic drug molecules followed by medicinal chemistry could be prudent. This review highlights such "sulfonamide-phytochemical" hybrid drug development research works for utilizing inactive sulfonamides and phytochemicals; the ingenious cost-effective and resource-saving hybrid drug concept could be a new trend in current antibacterial drug discovery to reactive the obsolete antibacterials., (© 2020 Wiley Periodicals LLC.)

From July 2017 to Jan 2019, a total of 572 retail fresh vegetables were collected to clarify the contamination of Salmonella in the Mekong Delta, Vietnam. Salmonella was isolated from 74 (12.9%) of 572 samples. The isolation rate of Salmonella from retail fresh vegetables in the rainy season (15.3%) was significantly higher than that in the dry season (7.6%) (P < 0.05). Of 74 Salmonella isolates, Salmonella Weltevreden was the most predominant serovar (35.1%) identified from retail fresh vegetables in all of the wet markets. All S. Weltevreden isolates (100%) were susceptible to nine antibiotics examined. Thus, retail fresh vegetables were considered as an important potential vehicle of Salmonella transmission to humans in the Mekong Delta. These results provide important data for preventing and controlling human salmonellosis in this area., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The outer membrane (OM) of Gram-negative bacteria provides an efficient barrier against external noxious compounds such as antimicrobial agents. Associated with drug target modification, it contributes to the overall failure of chemotherapy. In the complex OM architecture, Lipid A plays an essential role by anchoring the lipopolysaccharide in the membrane and ensuring the spatial organization between lipids, proteins, and sugars. Currently, the targets of almost all antibiotics are intracellularly located and require translocation across membranes. We report herein an integrated view of Lipid A synthesis, membrane assembly, a structure comparison at the molecular structure level of numerous Gram-negative bacterial species, as well as its recent use as a target for original antibacterial molecules. This review paves the way for a new vision of a key membrane component that acts during bacterial adaptation to environmental stresses and for the development of new weapons against microbial resistance to usual antibiotics.

Before the coronavirus 2019 (COVID-19) pandemic began, antimicrobial resistance (AMR) was among the top priorities for global public health. Already a complex challenge, AMR now needs to be addressed in a changing healthcare landscape. Here, we analyse how changes due to COVID-19 in terms of antimicrobial usage, infection prevention, and health systems affect the emergence, transmission, and burden of AMR. Increased hand hygiene, decreased international travel, and decreased elective hospital procedures may reduce AMR pathogen selection and spread in the short term. However, the opposite effects may be seen if antibiotics are more widely used as standard healthcare pathways break down. Over 6 months into the COVID-19 pandemic, the dynamics of AMR remain uncertain. We call for the AMR community to keep a global perspective while designing finely tuned surveillance and research to continue to improve our preparedness and response to these intersecting public health challenges., Competing Interests: GK, RG, CM, IO, KG, QL, NF, SW, RH, Ev, CC No competing interests declared, (© 2021, Knight et al.)

Phenomenological relations such as Ohm's or Fourier's law have a venerable history in physics but are still scarce in biology. This situation restrains predictive theory. Here, we build on bacterial "growth laws," which capture physiological feedback between translation and cell growth, to construct a minimal biophysical model for the combined action of ribosome-targeting antibiotics. Our model predicts drug interactions like antagonism or synergy solely from responses to individual drugs. We provide analytical results for limiting cases, which agree well with numerical results. We systematically refine the model by including direct physical interactions of different antibiotics on the ribosome. In a limiting case, our model provides a mechanistic underpinning for recent predictions of higher-order interactions that were derived using entropy maximization. We further refine the model to include the effects of antibiotics that mimic starvation and the presence of resistance genes. We describe the impact of a starvation-mimicking antibiotic on drug interactions analytically and verify it experimentally. Our extended model suggests a change in the type of drug interaction that depends on the strength of resistance, which challenges established rescaling paradigms. We experimentally show that the presence of unregulated resistance genes can lead to altered drug interaction, which agrees with the prediction of the model. While minimal, the model is readily adaptable and opens the door to predicting interactions of second and higher-order in a broad range of biological systems., Competing Interests: The authors have declared that no competing interests exist.

Background: The treatment of infection caused by pathogenic bacteria becomes one of the serious concerns globally. The failure in the treatment was found due to the exhibition of multiple resistance mechanisms against the antimicrobial agents. The emergence of resistant bacterial species has also been observed due to prolong treatment using conventional antibiotics. To combat these problems, several alternative strategies have been employed using biological and chemically synthesized compounds as antibacterial agents. Marine organisms are considered as one of the potential sources for the isolation of bioactive compounds due to the easily available, cost-effective, and eco-friendly., Methods: The online search methodology was adapted for the collection of information related to the antimicrobial properties of marine-derived compounds. These compound has been isolated and purified by different purification techniques, and their structure also characterized. Furthermore, the antibacterial activities have been reported by using broth microdilution as well as disc diffusion assays., Results: The present review paper describes the antimicrobial effect of diverse secondary metabolites which are isolated and purified from the different marine organisms. The structural elucidation of each secondary metabolite has also been done in the present paper, which will help for the in silico designing of the novel and potent antimicrobial compounds., Conclusion: A thorough literature search has been made and summarizes the list of antimicrobial compounds that are isolated from both prokaryotic and eukaryotic marine organisms. The information obtained from the present paper will be helpful for the application of marine compounds as antimicrobial agents against different antibiotic-resistant human pathogenic bacteria., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Objective: To investigate the pathogens' distribution and antimicrobial resistance in the bile of acute biliary tract infection patients. Methods: The data of bile bacterial culture and drug sensitivity test of 223 acute biliary tract infection patients who underwent gallbladder puncture or endoscopic retrograde cholangiopancreatography drainage from July 2009 to July 2019 were analyzed retrospectively at Department of General Surgery,Xinhua Hospital,Affiliated to Shanghai Jiao Tong University School of Medicine.There were 141 males and 82 females with age of 67.3 years(range:28 to 93 years).Three to five milliliter of bile was extracted from each patient and sent to the laboratory for bacterial culture,identification and drug sensitivity test.The patients were divided into two groups according to the visiting time: the former group ( n =124) was admitted from July 2009 to July 2014,and the latter group( n =99) was admitted from August 2014 to July 2019.The distribution of pathogenic bacteria and the changing trend of drug resistance rate of common bacteria in the two groups were compared.The results of drug sensitivity test were analyzed by WHONET software provided by WHO bacterial surveillance network.The drug resistance rates in different time periods were compared by χ 2 test. Results: In this study,there were 147 cases of acute cholangitis and 76 cases of acute cholecystitis.A total of 376 strains of pathogenic bacteria were cultured.Among them,98 strains(26.1%) were gram-positive bacteria,269 strains(71.5%) were gram-negative bacteria and 9 strains(2.4%) were fungi.The top three gram-positive bacteria were Enterococcus faecium (49.0%,48/98), Enterococcus faecalis (20.4%,20/98),and Enterococcus luteus (7.1%,7/98).The top 5 gram-negative bacteria were Escherichia coli (33.5%,90/269), Klebsiella pneumoniae (13.8%,37/269), Pseudomonas aeruginosa (13.0%,35/269), Acinetobacter baumannii (12.6%,34/269),and Enterobacter cloacae (4.8%,13/269).From 2009 to 2019,there was no significant change in the proportion of gram-positive bacteria (former group vs. latter group: 25.3% vs. 28.2%) and gram-negative bacteria(former group vs. latter group: 74.7% vs. 71.8%) in the bile of patients with acute biliary tract infection.Gram-positive bacteria were mainly Enterococci (85.7%,84/98) and gram-negative bacteria were Escherichia coli (33.5%,90/269). Acinetobacter baumannii accounted for 7.8%(11/142) of gram-negative bacteria in the former group and 18.1%(23/127) in the latter group,an increase of 10.3% over previous five years. Pseudomonas aeruginosa had a downward trend,16.9% in the former group(24/142) and 8.7% in the latter group (11/127),the proportion decreased by 8.2%,and the other changes were not significant.The drug resistance rates of common gram-positive bacteria were relatively stable,and the drug resistance rates of Enterococcus faecium to many antibiotics were higher than those of Enterococcus faecalis .The resistance rates of gram-negative bacteria to most antibiotics showed an upward trend,among which Klebsiella pneumoniae showed an upward trend to most of antibiotics(former group: 0/15－4/13, latter group: 55.0%－70.0%; χ 2 =3.996－16.942, P =0.000－0.046).The drug resistance rates of Acinetobacter baumannii was generally higher,but there were no significant changes in the drug resistance rates of Acinetobacter baumannii between the two groups.The drug resistance rates of Pseudomonas aeruginosa to most antibiotics increased,and the overall drug resistance rates of Escherichia coli were stable and showed a slight upward trend. Conclusions: The main pathogens in bile of patients with acute biliary tract infection are gram-negative bacteria.The constituent ratio of various gram-negative bacteria had no significant change from 2009 to 2019,but the drug resistance rates shows an upward trend.Among the gram-negative bacteria, Escherichia coli is the most important pathogen,and the proportion has no significant change.The proportion of Acinetobacter baumannii in the former group was significantly higher than that in the former group.And the proportion of Pseudomonas aeruginosa has a decreased trend.

This study was conducted to reveal the genotyping, antimicrobial susceptibility, and biofilm formation of Bacillus cereus isolated from powdered food products in China. Five hundred powdered food samples were collected from five provinces in China: 100 samples each of powdered infant formula (PIF), soy milk powder (SMP), lotus root powder (LRP), walnut powder (WP), and rice flour (RF). The genotyping of isolates was analyzed using multilocus sequence typing; meanwhile, antimicrobial susceptibility, and ability of biofilms formation on stainless steel tube of isolates were evaluated. Forty-two B. cereus strains were detected with an overall contamination rate of 8.4%, as well as, the highest B. cereus contamination rate was found in SMP (10%), followed by LRP (9%), WP (9%), RF (8%), and PIF (6%). These isolates were divided into 22 sequence types (STs); among them, ST32 (4/42, 9.5%) was the predominant ST. Phylogenetic relationships showed that the 42 strains of B. cereus were divided into three groups (group I, group II, and group III). Antimicrobial susceptibility testing indicated that all isolates were susceptible to tetracycline, gentamicin, erythromycin, and chloramphenicol, while resistant to ampicillin, cefepime, oxacillin, and rifampin. The analysis of ability of biofilm formation on stainless steel tube showed optical density (OD) 595 value of 66.7% of B. cereus isolates was greater than 1. The OD 595 level of isolates belonging to group III was higher compared with the other two groups, and OD 595 values of B. cereus HB1 and HN5 were greater than 2. These findings improved the understanding of the characteristics of B. cereus isolated from powdered food products in China, and provided a theoretical basis for the prevention and control of B. cereus in food industry.

Introduction: Infectious diseases have been responsible for an increasing number of deaths worldwide. Staphylococcus aureus has been recognized as one of the most notable causative agents of severe infections, while efflux pump (EP) expression is one of the main mechanisms associated with S. aureus resistance to antibiotics., Objective: This study aimed to investigate the potential of &#945;-pinene as an efflux pump inhibitor in species of S. aureus carrying the TetK and MrsA proteins., Methods: The minimum inhibitory concentrations (MIC) of &#945;-pinene and other efflux pump inhibitors were assessed using serial dilutions of each compound at an initial concentration above 1024 μg/mL. Solutions containing culture medium and bacterial inoculums were prepared in test tubes and subsequently transferred to 96-well microdilution plates. The modulation of ethidium bromide (EtBr) and antibiotics (tetracycline and erythromycin) was investigated through analysis of the modification in their MICs in the presence of a subinhibitory concentration of &#945;-pinene (MIC/8). Wells containing only culture medium and bacterial inoculums were used as negative control. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) was used as a positive control., Results: The MIC of ethidium bromide against S. aureus strains RN-4220 and IS-58 was reduced by association with α-pinene. This monoterpene potentiated the effect of tetracycline against the IS-58 strain but failed in modulating the antibacterial effect of erythromycin against RN-4220, suggesting a selective inhibitory effect on the TetK EP by &#945;- pinene., Conclusion: In conclusion, α-pinene has promising effects against S.aureus strains, which should be useful in the combat of antibacterial resistance associated with EP expression. Nevertheless, further research is required to fully characterize its molecular mechanism of action as an EP inhibitor., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

The objective of this study was to evaluate the clinical outcomes and safety of clindamycin combination antibiotherapy for the treatment of erythromycin-resistant, lincosamide-susceptible bone and joint infections caused by Staphylococcus spp. Between January 2010 and September 2018, 46 patients with Staphylococcus spp. erythromycin-resistant, lincosamide-susceptible bone and joint infections were treated with clindamycin combination antibiotherapy for 6 to 12 weeks. The type of infection was prosthetic in 20 cases (43.5%), osteosynthetic device in 15 cases (32.6%), chronic osteomyelitis in 7 cases (15.2%), and arthritis in 4 cases (8.7%). The cure rate was 67.4% by intention to treat and 84.6% per protocol, with a median follow-up of 398 days (range 86-843). Only 2 relapses (5.1%) were observed in patients with chronic osteomyelitis; an acquired resistance to lincosamides developed in 1 case. Clindamycin combination therapy appears to be effective for the treatment of bone and joint infection caused by erythromycin-resistant, lincosamide-susceptible Staphylococcus spp., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: The proportion of infections among young children that are antimicrobial-resistant is increasing across the globe. Newborns may be colonized with enteric antimicrobial-resistant pathogens early in life, which is a risk factor for infection-related morbidity and mortality. Breastfeeding is actively promoted worldwide for its beneficial impacts on newborn health and gut health. However, the role of breastfeeding and human milk components in mitigating young children's carriage of antimicrobial-resistant pathogens and antibiotic resistance genes has not been comprehensively explored., Main Body: Here, we review how the act of breastfeeding, early breastfeeding, and/or human milk components, such as the milk microbiota, secretory IgA, human milk oligosaccharides, antimicrobial peptides, and microRNA -bearing extracellular vesicles, could play a role in preventing the establishment of antimicrobial-resistant pathogens in young children's developing gut microbiomes. We describe findings from recent human studies that support this concept., Conclusion: Given the projected rise in global morbidity and mortality that will stem from antimicrobial-resistant infections, identifying behavioral or nutritional interventions that could decrease children's susceptibility to colonization with antimicrobial-resistant pathogens may be one strategy for protecting their health. We suggest that breastfeeding and human milk supplements deserve greater attention as potential preventive measures in the global effort to combat antimicrobial resistance, particularly in low- and middle-income settings.

Methicillin-resistant Staphylococcus spp. (MRS) have been identified in several foods, including dairy products. Studies are needed about their occurrence and genetic diversity in the dairy production chain in order to gain a better understanding of their epidemiology and control. This study therefore focuses on isolating and characterizing MRS strains detected in milk used in the production of Brazilian artisanal unpasteurized cheeses. To this end, samples were collected from bovine feces, the hands of milkmen, milking buckets, sieves, unpasteurized milk, whey, water, artisanal unpasteurized cheeses, cheese processing surfaces, cheese handlers, cheese trays, cheese molds, and skimmers at five dairy farms located in the state of São Paulo, Brazil. Colonies suggestive of Staphylococcus spp. were subjected to multiplex PCR to confirm the presence of Staphylococcus aureus and to detect the mecA gene. Sixteen isolates containing mecA gene were detected in samples from unpasteurized cheese and from cheese handlers. None of these isolates were positive to enterotoxin genes. These 16 isolates were subjected to antimicrobial susceptibility tests, which revealed they were resistant to oxacillin, penicillin, and cefepime. Using gene sequencing, the MRS isolates were identified as S. haemolyticus, S. hominis , and S. epidermidis . Furthermore, isolates from cheese handlers' hands and artisanal unpasteurized cheese presented high genetic similarity by random amplified polymorphic DNA (RAPD-PCR) analysis, which indicates cross contamination during cheese production. Thus, we found that people directly involved in milking and cheese processing activities at small dairy farms are a potential source of contamination of MRS strains in unpasteurized milk and cheese, representing a risk to public health.

Bacteria respond to changes in environmental conditions through adaptation to external cues. Frequently, bacteria employ nucleotide signaling molecules to mediate a specific, rapid response. Cyclic di-AMP (c-di-AMP) was recently discovered to be a bacterial second messenger that is essential for viability in many species. In this review, we highlight recent work that has described the roles of c-di-AMP in bacterial responses to various stress conditions. These studies show that depending on the lifestyle and environmental niche of the bacterial species, the c-di-AMP signaling network results in diverse outcomes, such as regulating osmolyte transport, controlling plant attachment, or providing a checkpoint for spore formation. c-di-AMP achieves this signaling specificity through expression of different classes of synthesis and catabolic enzymes as well as receptor proteins and RNAs, which will be summarized., (Copyright © 2020 American Society for Microbiology.)

Introduction: Actively dispersed Pseudomonas aeruginosa biofilm cells differ from planktonic cells, as they have a lower intracellular cyclic di-guanosine monophosphate (c-di-GMP) concentration and show increased virulence. In addition, the nature of the dispersion trigger has been shown to influence the antibiotic susceptibility of dispersed cells. However, properties of passively-dispersed cells, in which the dispersion trigger directly releases cells from the biofilm, have not been described. The present study determined c-di-GMP concentration, virulence in Galleria mellonella and antibiotic susceptibility of P. aeruginosa cells dispersed from biofilm using various triggers., Materials and Methods: P. aeruginosa biofilms grown in flow-cells were dispersed actively [exposure to the nitric oxide (NO)-donor sodium nitroprusside (SNP) or to glutamate] or passively [by stopping and restarting the flow or exposure to laser-induced vapor nanobubbles (VNB)], and properties of these dispersed cells were compared to those of spontaneously-dispersed cells., Results: The passively dispersed P. aeruginosa biofilm cells had significantly lower intracellular c-di-GMP levels than actively-dispersed cells. However, this did not result in differences in virulence in Galleria mellonella, nor in tobramycin and ciprofloxacin susceptibility. Passively-dispersed cells were more susceptible to colistin than actively- and spontaneously-dispersed cells. In cells dispersed by interrupting the flow, increased susceptibility to colistin was immediate, whereas this was delayed for VNB-dispersed cells., Conclusion: Passively-dispersed P. aeruginosa biofilm cells have a decreased intracellular c-di-GMP concentration and an increased colistin susceptibility compared to actively-dispersed cells. No differences in virulence or susceptibility to tobramycin or colistin were observed., (Copyright © 2020. Published by Elsevier Ltd.)

Rifampicin is a broad-spectrum antibiotic that binds to the bacterial RNA polymerase (RNAP), compromising DNA transcription. Rifampicin resistance is common in several microorganisms and it is typically caused by point mutations in the gene encoding the β subunit of RNA polymerase, rpoB . Different rpoB mutations are responsible for various levels of rifampicin resistance and for a range of secondary effects. rpoB mutations conferring rifampicin resistance have been shown to be responsible for severe effects on transcription, cell fitness, bacterial stress response and virulence. Such effects have never been investigated in the marine pathogen Vibrio vulnificus , even though rifampicin-resistant strains of V. vulnificus have been isolated previously. Moreover, spontaneous rifampicin-resistant strains of V. vulnificus have an important role in conjugation and mutagenesis protocols, with poor consideration of the effects of rpoB mutations. In this work, effects on growth, stress response and virulence of V. vulnificus were investigated using a set of nine spontaneous rifampicin-resistant derivatives of V. vulnificus CMCP6. Three different mutations (Q513K, S522L and H526Y) were identified with varying incidence rates. These three mutant types each showed high resistance to rifampicin [minimal inhibitory concentration (MIC) >800 µg ml -1 ], but different secondary effects. The strains carrying the mutation H526Y had a growth advantage in rich medium but had severely reduced salt stress tolerance in the presence of high NaCl concentrations as well as a significant reduction in ethanol stress resistance. Strains possessing the S522L mutation had reduced growth rate and overall biomass accumulation in rich medium. Furthermore, investigation of virulence characteristics demonstrated that all the rifampicin-resistant strains showed compromised motility when compared with the wild-type, but no major effects on exoenzyme production were observed. These findings reveal a wide range of secondary effects of rpoB mutations and indicate that rifampicin resistance is not an appropriate selectable marker for studies that aim to investigate phenotypic behaviour in this organism.

Objectives: To identify preferences of the Swedish public regarding antibiotic treatment characteristics and the relative weight of antibiotic resistance in their treatment choices., Methods: A questionnaire including a discrete choice experiment questionnaire was answered by 378 Swedish participants. Preferences of the general public regarding five treatment characteristics (attributes) were measured: contribution to antibiotic resistance, cost, side effects, failure rate and treatment duration. Latent class analysis models were used to determine attribute-level estimates and heterogeneity in preferences. Relative importance of the attributes and willingness to pay for antibiotics with a lower contribution to antibiotic resistance were calculated from the estimates., Results: All attributes influenced participants' preferences for antibiotic treatment. For the majority of participants, contribution to antibiotic resistance was the most important attribute. Younger respondents found contribution to antibiotic resistance more important in their choice of antibiotic treatments. Choices of respondents with lower numeracy, higher health literacy and higher financial vulnerability were influenced more by the cost of the antibiotic treatment. Older respondents with lower financial vulnerability and health literacy, and higher numeracy found side effects to be most important., Conclusions: All attributes can be considered as potential drivers of antibiotic use by lay people. Findings also suggest that the behaviour of lay people may be influenced by concerns over the rise of antibiotic resistance. Therefore, stressing individual responsibility for antibiotic resistance in clinical and societal communication has the potential to affect personal decision making., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Daptomycin is a calcium-dependent cyclic lipodepsipeptide derived from the soil saprotroph Streptomyces roseosporus , and its antibiotic properties make it a key agent for treatment of drug-resistant Gram-positive infections. It is most commonly used clinically for the treatment of Gram-positive skin and skin structure infections (SSSI), Staphylococcus aureus bacteremia, and right-sided endocarditis infections associated with S. aureus , including methicillin resistant S. aureus (MRSA). It has also been used "off-label" for Enterococcal infections. There has been a tremendous amount of research investigating its mode of action, resistance mechanisms, and biosynthesis of this clinically important antimicrobial agent. Although we cover the latter aspects in detail, the primary focus of this review is to provide the most comprehensive and up-to-date reference for the medicinal chemist on the structure-activity-toxicity of this important class of lipopeptide antibiotics.

In recent times green tea (GT) consumption has increased, due to the numerous studies that indicate a wide variety of health benefits following its regular consumption. The aim of this study was to assess the bioburden (bacteria and fungi) of bulk and bags of GT marketed in Lisbon and to obtain a more refined fungal burden characterization, including azole resistance profile. The bacteriota in tea bags before boiling ranged from lower than the detection limit to 1770 CFU.g -1 , whereas in brew samples ranged from lower than the detection limit to 54.55 CFU.mL -1 . In bulk samples before boiling ranged from lower than the detection limit to 2636 CFU.g -1 , while after boiling ranged from lower than the detection limit to 72.73 CFU.mL -1 . Fungal contamination on tea bags before boiling ranged from lower than the detection limit to 66.67 CFU.g -1 and after boiling, all samples presented results lower than the detection limit. Concerning bulk samples before boiling ranged from lower than the detection limit to 96.97 CFU.g -1 , whereas after boiling ranged from lower the detection limit to 30.3 CFU.mL -1 . Before boiling, the most common fungal species in the bagged tea (90.91 CFU.g -1 ; 45.45%) and bulk samples (66.67 CFU.g -1 ; 91.67%) was Aspergillus section Nigri. Fungal diversity was higher on bulk samples than in tea bags. Aspergillus section Nigri and Rhizopus sp. growth was observed mostly on itraconazole-supplemented Sabouraud dextrose agar media, which require further investigation. Aspergillus sections Fumigati and Nidulantes were detected by using real time PCR, but not in the GT samples in which they were identified through culture-based methods. A significantly reduction of bacterial contamination after boiling was observed, however fungal contamination with toxigenic potential was observed before and after boiling. Future research work needs to characterize in detail the mycotoxins contamination to allow a risk-benefit assessment to estimate the human health benefits and risks following tea consumption and to support policy-actions, if and when needed. The results also suggest that the conditions how tea is packed can influence the fungal diversity and this variable should be further investigated., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Antibiotic resistance is mediated through several distinct mechanisms, most of which are relatively well understood and the clinical importance of which has long been recognized. Until very recently, neither of these statements was readily applicable to the class of resistance mechanism known as target protection, a phenomenon whereby a resistance protein physically associates with an antibiotic target to rescue it from antibiotic-mediated inhibition. In this Review, we summarize recent progress in understanding the nature and importance of target protection. In particular, we describe the molecular basis of the known target protection systems, emphasizing that target protection does not involve a single, uniform mechanism but is instead brought about in several mechanistically distinct ways.