Staphylococcus aureus infective endocarditis versus bacteremia strains: Subtle genetic differences at stake

AbstractInfective endocarditis (IE)(1) is a severe condition complicating 10–25% of Staphylococcus aureus bacteremia. Although host-related IE risk factors have been identified, the involvement of bacterial features in IE complication is still unclear. We characterized strictly defined IE and bacteremia isolates and searched for discriminant features. S. aureus isolates causing community-acquired, definite native-valve IE (n=72) and bacteremia (n=54) were collected prospectively as part of a French multicenter cohort. Phenotypic traits previously reported or hypothesized to be involved in staphylococcal IE pathogenesis were tested. In parallel, the genotypic profiles of all isolates, obtained by microarray, were analyzed by discriminant analysis of principal components (DAPC)(2). No significant difference was observed between IE and bacteremia strains, regarding either phenotypic or genotypic univariate analyses. However, the multivariate statistical tool DAPC, applied on microarray data, segregated IE and bacteremia isolates: IE isolates were correctly reassigned as such in 80.6% of the cases (C-statistic 0.83, P<0.001). The performance of this model was confirmed with an independent French collection IE and bacteremia isolates (78.8% reassignment, C-statistic 0.65, P<0.01). Finally, a simple linear discriminant function based on a subset of 8 genetic markers retained valuable performance both in study collection (86.1%, P<0.001) and in the independent validation collection (81.8%, P<0.01). We here show that community-acquired IE and bacteremia S. aureus isolates are genetically distinct based on subtle combinations of genetic markers. This finding provides the proof of concept that bacterial characteristics may contribute to the occurrence of IE in patients with S. aureus bacteremia

A new mechanism to render clinical isolates of Escherichia coli non-susceptible to imipenem: substitutions in the PBP2 penicillin-binding domain

International audienceObjectives: So far, two types of mechanism are known to be involved in carbapenem non-susceptibility of Escherichia coli clinical isolates: reduced outer membrane permeability associated with production of ESBLs and/or overproduction of class C beta-lactamases; and production of carbapenemases. Non-susceptibility to only imipenem observed in two clinical isolates suggested a new mechanism, described in the present study.Methods: The ST was determined for the two isolates of E. coli (strains LSNy and VSBj), and their chromosomal region encoding the penicillin-binding domain of PBP2 was amplified, sequenced and then used for recombination experiments in E. coli K12 C600. Antibiotic MICs were determined using the Etest method.Results: Strains LSNy and VSBj, which displayed ST23 and ST345, respectively, showed amino acid substitutions in their PBP2 penicillin-binding domain. Substitution Ala388Ser located in motif 2 (SXD) was common to the two strains. Two additional substitutions (Ala488Thr and Leu573Val) located outside the two other motifs were identified in strain LSNy, whereas another one (Thr331Pro) located in motif 1 was identified in strain VSBj. Recombination experiments to reproduce non-susceptibility to imipenem in E. coli K12 C600 were not successful when only the common substitution was transferred, whereas recombination with DNA fragments including either the three substitutions (strain LSNy) or the two substitutions (strain VSBj) were successful.Conclusions: Substitution of amino acids in the penicillin-binding domain of PBP2 is a new mechanism by which E. coli clinical isolates specifically resist imipenem

Hospital outbreak of P. aeruginosa producing extended-spectrum oxacillinase OXA-19.

International audienceThis report describes the microbiological investigation of an outbreak of P. aeruginosa producing the extended-spectrum OXA-19 in a French university hospital. The 48 isolates producing OXA-19 recovered from 27 patients were clustered into 3 PFGE patterns. The blaOXA-19 gene responsible for OXA-19 was a part of class 1 integron

Épidémiologie des souches d’entérobactéries productrices de BLSE isolées dans 18 hôpitaux français en 2012

National audienc

Evaluating antibiotic stewardship and healthcare-associated infections surveillance assisted by computer: protocol for an interrupted time series study

International audienceIntroduction Antibiotic resistance is one of the most pressing health threats that mankind faces now and in the coming decades. Antibiotic resistance leads to longer hospital stays, higher medical costs and increased mortality. In order to tackle antibiotic resistance, we will implement in our tertiary care university hospital a computerised-decision support system (CDSS) facilitating antibiotic stewardship and an electronic surveillance software (ESS) facilitating infection prevention and control activities. We describe the protocol to evaluate the impact of the CDSS/ESS combination in adult inpatients. Methods and analysis We conduct a pragmatic, prospective, single-centre, before–after uncontrolled study with an interrupted time-series analysis 12 months before and 12 months after the introduction of the CDSS for antibiotic stewardship (APSS) and ESS for infection surveillance (ZINC). APSS and ZINC will assist, respectively, the antibiotic stewardship and the infection prevention and control teams of Nancy University Hospital (France). We will evaluate the impact of the CDSS/ESS on the antibiotic use in adult (≥18 years) inpatients (hospitalised ≥48 hours). The primary outcome is the prescription rate by all healthcare professionals from the hospital of all systemic antibiotics expressed in defined daily doses/1000 patients/month. Concurrently, we will assess the safety of the intervention, its impact on the appropriateness of antibiotic prescriptions and on additional precautions (isolation precautions) as recommended in guidelines, and on bacterial epidemiology (multidrug-resistant bacteria and Clostridioides difficile infections) in the hospital. Finally, we will evaluate the users’ satisfaction and the cost of this intervention from the hospital perspective. Ethics and dissemination The protocol has been approved by the Ethics Committee of Nancy University Hospital and registered on the ClinicalTrials platform. Results will be disseminated through conferences’ presentations and publications in peer-reviewed journals. Trial registration number NCT04976829

Rapid identification of MSSA and MRSA on the bench: multicentre comparative evaluation of PBP2a Culture Colony Test(TM) (Alere) versus Slidex(R) MRSA detection (bioMérieux)

International audienc

Staphylococcus aureus infective endocarditis versus bacteremia strains: Subtle genetic differences at stake

International audienceInfective endocarditis (IE)((1)) is a severe condition complicating 10-25% of Staphylococcus aureus bacteremia. Although host-related IE risk factors have been identified, the involvement of bacterial features in IE complication is still unclear. We characterized strictly defined IE and bacteremia isolates and searched for discriminant features. S. aureus isolates causing community-acquired, definite native-valve IE (n=72) and bacteremia (n=54) were collected prospectively as part of a French multicenter cohort. Phenotypic traits previously reported or hypothesized to be involved in staphylococcal IE pathogenesis were tested. In parallel, the genotypic profiles of all isolates, obtained by microarray, were analyzed by discriminant analysis of principal components (DAPC)((2)). No significant difference was observed between IE and bacteremia strains, regarding either phenotypic or genotypic univariate analyses. However, the multivariate statistical tool DAPC, applied on microarray data, segregated IE and bacteremia isolates: IE isolates were correctly reassigned as such in 80.6% of the cases (C-statistic 0.83, P<0.001). The performance of this model was confirmed with an independent French collection IE and bacteremia isolates (78.8% reassignment, C-statistic 0.65, P<0.01). Finally, a simple linear discriminant function based on a subset of 8 genetic markers retained valuable performance both in study collection (86.1%, P<0.001) and in the independent validation collection (81.8%, P<0.01). We here show that community-acquired IE and bacteremia S. aureus isolates are genetically distinct based on subtle combinations of genetic markers. This finding provides the proof of concept that bacterial characteristics may contribute to the occurrence of IE in patients with S. aureus bacteremia

Inventory of extended-spectrum-β-lactamase-producing Enterobacteriaceae in France as assessed by a multicenter study

The objective of this study was to perform an inventory of the ESBL-producing Enterobacteriaceae isolates responsible for infections in French hospitals, and to assess the mechanisms associated with ESBL diffusion.200 non-redundant ESBL-producing Enterobacteriaceae strains isolated from clinical samples were collected during a multi-centric study performed in 18 representative French hospitals. Antibiotic resistance genes were identified by PCR and sequencing experiments. The clonal relatedness between isolates was investigated by the Diversilab system. ESBL-encoding plasmids were compared by PCR-based-replicon-typing and plasmid-multi-locus-sequence-typing.CTX-M-15, CTX-M-1, CTX-M-14 and SHV-12 were the most prevalent ESBLs (8 to 46.5%). The three CTX-M-type EBSLs were significantly observed in Escherichia coli (37.1%, 24.2% and 21.8% respectively), and CTX-M-15 was the predominant ESBL in Klebsiella pneumoniae (81.1%). SHV-12 was associated with ESBL-encoding Enterobacter cloacae strains (37.9%). qnrB, aac(6')-Ib-cr and aac (3)-II genes were the main plasmid-mediated resistance genes, with prevalence varying between 19.5 and 45% according to the ESBLs. Molecular typing did not identify wide clonal diffusion. Plasmid analysis suggested the diffusion of few numbers of ESBL-encoding plasmids, especially in K. pneumoniae and E. cloacae However, the ESBL-encoding genes were observed in different plasmid replicons according to the bacterial species.The prevalence of ESBL subtypes is different according to the Enterobacteriaceae species. Plasmid spread is a key determinant of this epidemiology and the link observed between the ESBL-encoding plasmids and the bacterial host explain the differences observed in the Enterobacteriaceae species