Temporal trends and risks factors for antimicrobial resistant Enterobacteriaceae urinary isolates from outpatients in Guadeloupe.

International audienceUrinary tract infections are bacterial infections most commonly encountered in the community. The resistance rate of uropathogens to commonly prescribed antibiotics has increased worldwide but there are no published data concerning the resistance of strains isolated from community-acquired UTI in Guadeloupe. To assess the susceptibility patterns of Enterobacteriaceae strains isolated from outpatients in Guadeloupe we conducted a prospective study from December 2012 to May 2014 among outpatients consulting at private and public laboratories for urine analysis. Risk factors for E. coli resistance to amoxicillin, third-generation cephalosporin, and ciprofloxacin were also determined. To study the trends of E. coli resistance rates over the past 10 years, data on the susceptibility patterns of E. coli from 2003 to 2014 were also collected from three major laboratories for a retrospective study. During the prospective study, we isolated 1293 bacterial strains from the urine of outpatients presenting for urine analysis. The most commonly isolated bacteria were E. coli (57 %) and Klebsiella pneumoniae (15.5 %). Thirty seven per cent of the E. coli strains were resistant to amoxicillin. Resistance rates to third generation cephalosporin were low for E. coli and other Enterobacteriaceae (3.1 and 12.2 % respectively) and mostly due to the presence of an Extended Spectrum Beta-lactamase. Resistance to cotrimoxazole and ciprofloxacin was moderate (17.8 and 15.6 % respectively). However, the resistance rate of E. coli to ciprofloxacin has significantly increased during the last 10 years. Risk factors were consistent with previously reported data, especially for the increasing ciprofloxacin resistance with age. General practitioners in Guadeloupe need to be better informed to favor the prescription of fosfomycin-trometamol to reduce the risk of resistance to fluoroquinolones

Caractérisation du Système à Cinq-Composants GraSRX/VraFG impliqué dans la résistance aux peptides antimicrobiens et la virulence chez Staphylococcus aureus

PARIS7-Bibliothèque centrale (751132105) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

GraXSR proteins interact with the VraFG ABC transporter to form a five-component system required for cationic antimicrobial peptide sensing and resistance in Staphylococcus aureus

International audienceThe GraSR two-component system (TCS) controls cationic antimicrobial peptide (CAMP) resistance in Staphylococcus aureus through the synthesis of enzymes that increase bacterial cell surface positive charges, by d-alanylation of teichoic acids and lysylination of phosphatidylglycerol, leading to electrostatic repulsion of CAMPs. The GraS histidine kinase belongs to the "intramembrane-sensing kinases" subfamily, with a structure featuring a short amino-terminal sensing domain, and two transmembrane helices separated only by a short loop, thought to be buried in the cytoplasmic membrane. The GraSR TCS is in fact a multicomponent system, requiring at least one accessory protein, GraX, in order to function, which, as we show here, acts by signaling through the GraS kinase. The graXRS genes are located immediately upstream from genes encoding an ABC transporter, vraFG, whose expression is controlled by GraSR. We demonstrated that the VraFG transporter does not act as a detoxification module, as it cannot confer resistance when produced on its own, but instead plays an essential role by sensing the presence of CAMPs and signaling through GraS to activate GraR-dependent transcription. A bacterial two-hybrid approach, designed to identify interactions between the GraXSR and VraFG proteins, was carried out in order to understand how they act in detecting and signaling the presence of CAMPs. We identified many interactions between these protein pairs, notably between the GraS kinase and both GraX and the VraG permease, indicating the existence of an original five-component system involved in CAMP sensing and signal transduction to promote S. aureus resistance

Investigation of the Staphylococcus aureus GraSR Regulon Reveals Novel Links to Virulence, Stress Response and Cell Wall Signal Transduction Pathways

The GraS/GraR two-component system has been shown to control cationic antimicrobial peptide (CAMP) resistance in the major human pathogen Staphylococcus aureus. We demonstrated that graX, also involved in CAMP resistance and cotranscribed with graRS, encodes a regulatory cofactor of the GraSR signaling pathway, effectively constituting a threecomponent system. We identified a highly conserved ten base pair palindromic sequence (59 ACAAA TTTGT 39) located upstream from GraR-regulated genes (mprF and the dlt and vraFG operons), which we show to be essential for transcriptional regulation by GraR and induction in response to CAMPs, suggesting it is the likely GraR binding site. Genome-based predictions and transcriptome analysis revealed several novel GraR target genes. We also found that the GraSR TCS is required for growth of S. aureus at high temperatures and resistance to oxidative stress. The GraSR system has previously been shown to play a role in S. aureus pathogenesis and we have uncovered previously unsuspected links with the AgrCA peptide quorum-sensing system controlling virulence gene expression. We also show that the GraSR TCS controls stress reponse and cell wall metabolism signal transduction pathways, sharing an extensive overlap with the WalKR regulon. This is the first report showing a role for the GraSR TCS in high temperature and oxidative stress survival and linking thi

Bacitracin and nisin resistance in Staphylococcus aureus: A novel pathway involving the BraS/BraR two-component system (SA2417/SA2418) and both the BraD/BraE and VraD/VraE ABC transporters

21 p., 6 tables, 7 figures and bibliographyTwo-component systems (TCSs) are key regulatory pathways allowing bacteria to adapt their genetic expression to environmental changes. Bacitracin, a cyclic dodecylpeptide antibiotic, binds to undecaprenyl pyrophosphate, the lipid carrier for cell wall precursors, effectively inhibiting peptidoglycan biosynthesis. We have identified a novel and previously uncharacterized TCS in the major human pathogen Staphylococcus aureus that we show to be essential for bacitracin and nisin resistance: the BraS/BraR system (Bacitracin resistance associated; SA2417/SA2418). The braRS genes are located immediately upstream from genes encoding an ABC transporter, accordingly designated BraDE. We have shown that the BraSR/BraDE module is a key bacitracin and nisin resistance determinant in S. aureus. In the presence of low antibiotic concentrations, BraSR activate transcription of two operons encoding ABC transporters: braDE and vraDE. We identified a highly conserved imperfect palindromic sequence upstream from the braDE and vraDE promoter sequences, essential for their transcriptional activation by BraSR, suggesting it is the likely BraR binding site. We demonstrated that the two ABC transporters play distinct and original roles in antibiotic resistance: BraDE is involved in bacitracin sensing and signalling through BraSR, whereas VraDE acts specifically as a detoxification module and is sufficient to confer bacitracin and nisin resistance when produced on its own. We show that these processes require functional BraD and VraD nucleotide-binding domain proteins, and that the large extracellular loop of VraE confers its specificity in bacitracin resistance. This is the first example of a TCS associated with two ABC transporters playing separate roles in signal transduction and antibiotic resistance.This work was supported by research funds from the European Commission [StaphDynamics (LHSM-CT-2006-019064) and BaSysBio (LSHG-CT-2006-037469) grants], the Centre National de la Recherche Scientifique (CNRS URA 2172), Agence Nationale de la Recherche (ANR GrabIron and NaBab) and the Institut Pasteur (PTR N°256 and PTR N°336)

High genetic diversity of extended-spectrum β-lactamases producing Escherichia coli in feces of horses

International audienceExtended-spectrum beta-lactamases (ESBLs), especially those of the CTX-M type, represent a major public health problem throughout the world. Although the carriage of ESBL-producing Enterobacteriaceae (EPE) in feces of horses is now well recognized, little is known about the diversity of EPE after treatment of horses with antibiotics. We undertook this study to assess and follow the diversity of EP Escherichia coli isolated from horses after antibiotic treatment for an infection. Fecal samples from two horses treated and two that were untreated were tested for the presence of EPE on different days. All isolated E. coli strains were evaluated for antimicrobial resistance (AMR) and by whole-genome sequencing. Multi locus sequence typing, phylogrouping, resistance genes and plasmid content were extracted from genomic data. A phylogenetic analysis based on single nucleotide polymorphism (SNP) divergence was also performed on the core genome. We isolated 35 strains belonging to the A, B1 and C phylo-groups. All but one expressed SHV-12 enzymes and one expressed CTX-M-1. Intra- and inter-horse genetic diversity of E. coli strains was identified in the genome analysis and 10 AMR profiles. Two distinct EP E. coli-resistant populations (phylo-group B1: ST4164-AMR3 and ST155-AMR2) were found in one horse, and five other resistant populations were found in the second horse (phylo-group A: ST1250-AMR1; phylo-group B1: ST1250-AMR1, ST6981-AMR1 and phylo-group C: ST10-AMR4). Some persistent EP E. coli strains were detected at least 1 month after treatment. These results indicate that EP E. coli strains isolated from horse feces show intra- and inter-host genetic diversity, even in a region with low ESBL prevalence and in horses that are rarely treated with third-generation cephalosporins. These results also suggest that horizontal gene transfer and/or selection of resistance genes probably occurs in vivo within the horse gut microbiome. Follow-up of EP E. coli resistance profiles for at least 1 month after treatment is warranted to prevent persistence of EP E. coli

Comparative study of two plasticins: specificity, interfacial behavior, and bactericidal activity.

International audienceA comparative study was designed to evaluate the staphylococcidal efficiency of two sequence-related plasticins from the dermaseptin superfamily we screened previously. Their bactericidal activities against Staphylococcus aureus as well as their chemotactic potential were investigated. The impact of the GraS/GraR two-component system involved in regulating resistance to cationic antimicrobial peptides (CAMPs) was evaluated. Membrane disturbing activity was quantified by membrane depolarization assays using the diS-C3 probe and by membrane integrity assays measuring beta-galactosidase activity with recombinant strain ST1065 reflecting compromised membranes and cytoplasmic leakage. Interactions of plasticins with membrane models composed of either zwitterionic lipids mimicking the S. aureus membrane of CAMP-resistant strains or anionic lipids mimicking the negative charge-depleted membrane of CAMP-sensitive strains were analyzed by jointed Brewster angle microscopy (BAM), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and differential scanning calorimetry (DSC) to yield detailed information about the macroscopic interfacial organization, in situ conformation, orientation of the peptides at the lipid-solvent interface, and lipid-phase disturbance. We clearly found evidence of distinct interfacial behaviors of plasticins we linked to the distribution of charges along the peptides and structural interconversion properties at the membrane interface. Our results also suggest that amidation might play a key role in GraS/GraR-mediated CAMP sensing at the bacterial surface

Influence of soil fertilization with composted organic amendments on resistance dissem-ination in crop production

International audienceThe selection pressure related to the overuse of antibiotics in human and veterinary medicines is responsi-ble for the increasing of antibiotic resistance, but the environment also plays a role in the resistance dis-semination. In Guadeloupe, a French overseas department, organic amendments resulting from human and animal wastes are widely used in soils fertilization. The objectives of this project were (i) to evaluate the impact of organic amendments on the selection and the diffusion of antibiotic resistant bacteria (ARBs) and antibiotic resistance genes (ARGs) in soils and crop production.The study was carried out over three vegetable crops sessions (cucumbers and sweet potatoes) on amend-ed or non-amended plots. Two hundred and seven samples, including intrants, biosolids, soils and vege-tables, were collected between March 2015 and February 2017. Samples were cultured on media with or without antibiotics. ARBs identification (isolation, count, antimicrobial testing, MALDI-TOF mass spec-trometry), and ARGs molecular characterization: extended spectrum β-lactamase (ESBL), cephalospori-nase (CASE) coding genes, sulphonamid and quinolone plasmidic resistances were performed.Our results showed that enterobacteria concentrations were higher in poultry droppings than in horse fe-ces or sewage sludge. Resistant enterobacteria were also more frequent in poultry droppings. After com-posting, the concentration of enterobacteria drastically decreased and resistant enterobacteria were only detected in one compost sample. Resistant enterobacteria were beneath our detection limit in soil and vegetable samples. Concerning the resistance genes, ESBL were more frequent in E. coli isolated from poultry droppings but resistance to sulfonamide was more frequent in horse feces. ESBL genes detected were different in poultry droppings (CTX-M1 mainly) and in horses feces (mainly SHV-12).Our study confirms the efficiency of composting process to decrease the number of enterobacteria and to reduce the risk of antibiotic resistance diffusion in soils and vegetables. Our study also suggests that ARGs, conferring ESBL phenotype, are biotope specific and that the exchange of genes between bio-topes may not be so easy