Genotypic diversity of coagulase-negative staphylococci causing endocarditis: a global perspective.

Coagulase-negative staphylococci (CNS) are important causes of infective endocarditis (IE), but their microbiological profiles are poorly described. We performed DNA target sequencing and susceptibility testing for 91 patients with definite CNS IE who were identified from the International Collaboration on Endocarditis-Microbiology, a large, multicenter, multinational consortium. A hierarchy of gene sequences demonstrated great genetic diversity within CNS from patients with definite endocarditis that represented diverse geographic regions. In particular, rpoB sequence data demonstrated unique genetic signatures with the potential to serve as an important tool for global surveillance.

Molecular epidemiology of Enterobacteriaceae producing extended-spectrum beta-lactamase in a French university-affiliated hospital.

We conducted a retrospective study to investigate the epidemiology of Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBLE) in our hospital. We determined the occurrence of extended-spectrum beta-lactamase (ESBL) in Enterobacteriaceae over a 2-year period. We also characterised ESBLs by isoelectric focusing (IEF) and investigated the epidemiological relatedness of EBLSE by pulsed field gel electrophoresis (PFGE). During this period, 70 patients were colonised/infected with one or several strains of EBLSE, giving a crude incidence of 0.095 per 1000 patient-days. We found that ESBL-producing Enterobacter aerogenes were the main source of ESBLE dissemination. Indeed, 59.5% of ESBLE were E. aerogenes and 21.9% of the other ESBLE resulted from a plasmid transfer originating from E. aerogenes. IEF and PFGE analysis demonstrated that the dissemination of ESBL from E. aerogenes in our hospital was due to a single clone that always harbours TEM-24. This emphasises the importance of standard contact isolation precautions and the early detection of ESBLE-colonised patients in high risk departments like intensive care units.

Bacteraemia caused by coagulase-negative staphylococci exhibiting decreased susceptibility to teicoplanin.

The purpose of our study was to assess the prevalence of coagulase-negative staphylococci (CoNS) isolates with reduced susceptibility to glycopeptides among the isolates responsible for bloodstream infections and to describe the epidemiology of these isolates. CoNS isolates from bloodstream infections were collected and characterized by analysis of antibiotic susceptibility and restriction fragment length polymorphism using pulsed-field gel electrophoresis. The medical records of patients with positive cultures and trends in glycopeptide use were reviewed to determine the effect of previous antibiotic treatment on the susceptibility profile of these organisms. The crude incidence of CoNS bacteraemia was 0.51 per 1000 days of hospitalization. The 15 (28.8%) strains identified as having decreased susceptibility to teicoplanin by the reference method were all hospital-acquired and displayed 13 different DNA patterns. The relative risk of harbouring strains with decreased susceptibility to teicoplanin was 3.55 among patients previously treated with vancomycin (confidence interval 95%: 2.15-5.85). The teicoplanin consumption in our institution was constant and represented about 27% of the glycopeptide consumption in daily defined doses. The implementation of programmes aiming to reduce the unnecessary use of glycopeptides should have a significant impact on the reduced-susceptibility rate because strains probably become resistant as a result of antibiotic pressure.

Characterisation of coagulase-negative staphylococci isolated from blood infections: incidence, susceptibility to glycopeptides, and molecular epidemiology.

The purpose of this study was to determine incidence of coagulase-negative staphylococci (CNS) bacteraemia and to characterise the epidemiology of isolates with reduced susceptibility to glycopeptides. CNS isolates from bloodstream infections were collected and characterised by determination of the species, analysis of antibiotic susceptibility, and restriction fragment length polymorphism using pulsed-field gel electrophoresis. The medical records of patients with positive cultures and the trends in glycopeptide use were reviewed to determine the effect of previous antibiotic treatment on the susceptibility profile of these organisms. The incidence of bacteraemia caused by CNS was 0.26 per 100 patients or 0.36 per 1,000 days of hospitalisation. According to genomic fingerprinting typing, 41 (67.2%) cases of bacteraemia were caused by a unique strain of CNS and 20 were caused by several strains. Nineteen of the 61 cases of bacteraemia studied were caused by an isolate with decreased susceptibility to teicoplanin. Genomic DNA analysis of the 90 CNS isolates recovered from the 61 cases of bacteraemia generated 50 unique profiles (1 isolate per major PFGE pattern) and 13 multiple profiles (several isolates per major PFGE pattern). Neither decreased susceptibility of an isolate to teicoplanin nor hospital acquisition was associated with a multiple profile. There was a significant correlation between the incidence of bacteraemia caused by CNS with decreased susceptibility to teicoplanin and glycopeptide use at the unit level but not in individual patients. Cross-transmission did not play an important role in the dissemination of CNS with decreased susceptibility to teicoplanin, thus strains probably become resistant as a result of antibiotic pressure. Prudent use of glycopeptides is necessary to minimise the spread of resistance to these agents.

[Bacteremia caused by coagulase-negative staphylococci: incidence, frequency of teicoplanin resistance and molecular epidemiology]. / Bactériémies liées aux staphylocoques à coagulase négative : incidence, niveau de résistance à la teicoplanine et épidémiologie moléculaire.

All the patients hospitalised at Besançon Hospital between October 2000 and December 2000 were included in a prospective study in order to determine the incidence of bloodstream infections caused by coagulase-negative staphylococci (CNS), the prevalence of decreased susceptibility to glycopeptides and the molecular epidemiology of these pathogens. CNS isolates from bloodstream infections were collected and characterised by analysis of antibiotic susceptibility and restriction fragment length polymorphism using pulsed field gel electrophoresis. Forty-five episodes of CNS bacteremia occurred in 43 patients. The crude incidence of infected patients was 0,51 per 1,000 days of hospitalisation. These 45 bacteremia represented 23.3% of the total number of bacteraemia. Forty three of 45 bacteremia were studied, 36 were positive with a single PFGE pattern, 5 bacteraemias with 2 PFGE patterns, and 2 bacteraemias with 3 PFGE patterns. We identified 52 distinct PFGE patterns and 42 major PFGE patterns (35 were isolated in a single patient, 5 in 2 patients and 2 in 3 patients). The dendrogram generated showed deep but limited branching, each large branch corresponding to a species. Of these CNS isolates, 28.8% and 25.0% showed decreased susceptibility to teicoplanin, with the reference method and E-test respectively. The 16 strains belonging to multiple PFGE patterns were not more resistant to teicoplanin. Clonal dissemination did not seem to play a major role in the spread of glycopeptides resistance among CNS.