Methicillin-resistant Staphylococcus aureus among a network of French private-sector community-based-medical laboratories.

OBJECTIVE: The aim of this study was to estimate the frequency of methicillin-resistant Staphylococcus aureus (MRSA) strains in the French community and the proportion of Panton-Valentine (PVL)-MRSA. DESIGN: A cross-sectional study was made during a 3-month period in 2003 through a network of private-sector, community-based medical laboratories selected throughout France: the Labville network. Each MRSA isolate was included and characterized by French National Reference Center for Staphylococci. The total number of S. aureus isolates was also collected. RESULTS: Among the 283 patients infected or colonized by MRSA, 166 (59%) were considered as healthcare-associated, 14 (5%) as nursing-associated and 39 (14%) as community-acquired. The proportion of methicillin resistance among S. aureus was 14%. Taking into account the sampling design, the incidence of MRSA cases in French outpatients was estimated to be 0.50 [CI95%: 0.41-0.60] per 10,000 inhabitants. The molecular analysis confirmed that 80.6% belong to the Lyon clone, the most prevalent hospital MRSA clone spreading in France and 10.6% to a closely related clone. An emerging MRSA clone containing the tst1 gene was detected in six patients and the PVL-positive ST80 clone only in one, 22-year-old, patient. CONCLUSION: Most of MRSA cases diagnosed in the community in France, in 2003, were elderly with specific risk factors and harbored hospital strains. The prevalence of PVL-MRSA remained low.

[Implementing a community surveillance network to monitor antimicrobial resistance: the Labville network]. / Mise en oeuvre d'un réseau de surveillance de la résistance bactérienne aux antibiotiques en ville: le réseau Labville.

BACKGROUND: In France, antimicrobial resistance monitoring is based on the contribution of many microbiological partners and networks, especially hospital laboratories. In order to complete this surveillance, the InVS implemented a network based on private-sector laboratories (PSL): the Labville network. METHOD: Stratified by French region, 69 PSL were randomly selected. The microbiological analysis results, including anonymized individual patient data, are translated into an appropriate data format within an automated reading process. This data is then sent to InVS through a secure Internet connection. RESULTS: The specifications of the automated system were defined according to a feasibility study conducted in 2003. The first stage of the project consisted in defining a global strategy for the reading of printed microbiological results. Then, the parameters were adapted for each PSL using a set of specific analysis over two to three weeks. After validation by InVS, the reading strategy was applied on to routinely printed results. The strategy was definitely validated after four month of a daily data transmission. The general approach needs to be adapted to each PSL and undergoes several adjustments. This long step of the project still requires microbiological expertise. CONCLUSION: The automated data extraction process used for Labville project is innovating. It is not affected by the compatibility and diversity of computing systems and reduces the biologist's workload. The Labville network is a challenging project motivating future development of other electronic surveillance networks.

Comparability of antimicrobial susceptibility test results from 22 European countries and Israel: an external quality assurance exercise of the European Antimicrobial Resistance Surveillance System (EARSS) in collaboration with the United Kingdom National External Quality Assurance Scheme (UK NEQAS).

The goal of this exercise was to organize external quality assurance (QA) of antibiotic susceptibility testing for laboratories participating in EARSS and to assess the comparability of susceptibility test results across countries, and guidelines. In September 2000, UK NEQAS distributed a set of three Streptococcus pneumoniae strains, two Staphylococcus aureus strains and one Streptococcus haemolyticus strain. Laboratories reported the guideline followed, the interpretation of the susceptibility test result and the MIC, if tested. In this study we considered results 'concordant' if the reported interpretation of the participating laboratory agreed with the designated interpretation of reference laboratories. Overall, 433 (92%) of 471 laboratories from 23 countries reported back. Of the 8685 tests that were assessed, 8322 (96%) were interpreted correctly by the participants. Concordance for detection of penicillin non-susceptibility in the three S. pneumoniae strains was 96%, 90% and 87%, respectively. Laboratories performed extremely well in detecting oxacillin resistance in the homogeneously methicillin-resistant S. aureus (MRSA) strain, but the concordance rate dropped from 100% to 77% in the heterogeneously resistant MRSA strain. Concordance for detection of teicoplanin resistance in the S. haemolyticus strain was 82%. We stratified concordance rates first for country and then for guideline used, but observed only minor differences among countries and guidelines. Quantitative methods yielding an MIC were more concordant than non-MIC methods for penicillin resistance in the S. pneumoniae strains (94% versus 79%). The NCCLS guideline was the most frequently followed, by 61% of laboratories from 19 countries. This exercise shows that, overall, countries participating in EARSS are capable of delivering susceptibility data of good quality. The comparability of susceptibility data for penicillin resistance in S. pneumoniae and for homogeneous methicillin resistance in S. aureus is satisfactory among European countries and across guidelines. However, we emphasize the importance of determining an MIC for suspected penicillin non-susceptible S. pneumoniae and for suspected glycopeptide non-susceptible S. aureus. Laboratories, particularly in some countries, may need to improve their capability to detect oxacillin resistance in heterogeneously resistant MRSA. For continuous external quality assessment we recommend that laboratories participate in national and international schemes with frequent distribution of control strains.

[Methicillin-resistant Staphylococcus aureus: factors responsible for its incidence]. / Staphylococcus aureus résistant à la méticilline: facteurs responsables de l'endémie.

INTRODUCTION: How can we explain that the proportion of methicillin-resistant Staphylococcus aureus (MRSA) varies between the European countries, ranging from < 1% in Scandinavia to > 30% in Spain, France and Italy? This paper is aimed at attempting to determine factors at the origin of the spreading of endemic MRSA strains as of the early 1980s. Those strains are characterized by their ability to develop resistance to current antibiotics and make treatment of severe and deep infections more complex. CURRENT KNOWLEDGE AND KEY POINTS: Differences in the virulence of MRSA strains and that of susceptible strains appear unlikely. MRSA prevalence seems to be a growing problem, especially in Southern Europe where rates of resistance to other anti-staphylococcal antibiotics are high. General policies for antibiotic therapy as well as the implementation of strategies for prevention and control of MRSA might be responsible for such rates. Indeed, once MRSA is introduced into a facility without control program, this multiresistant bacteria rapidly spreads within the hospital and becomes endemic, expanding its reservoir. FUTURE PROSPECTS ET PROJECTS: Due to the introduction of new methods in microbiology and communication, infection control measures including procedures for isolation and identification of MRSA reservoirs are still feasible; however, their implementation requires human and material resources. Areas requiring improvement in the detection of MRSA outbreaks are identified in this paper, with particular emphasis on the need for national surveillance of MRSA prevalence and reappraisal of MRSA control strategies in French hospitals.

Bacterial resistance to antibiotics in France : a public health priority.

For a few years, France has been faced to a rapid spread of anti-microbial resistance in hospitals and in general practice despite the many recommendations issued to solve this problem. In 1999, the Institut de Veille Sanitaire conducted a collective expe

Characterization of mutations in the rpoB gene that confer rifampin resistance in Staphylococcus aureus.

Mutations in the rifampin resistance-determining (Rif) regions of the rpoB gene of Staphylococcus aureus mutants obtained during therapy or in vitro were analyzed by gene amplification and sequencing. Each of the resistant clinical isolates, including five nonrelated clones and two strains isolated from the same patient, and of the 10 in vitro mutants had a single base pair change that resulted in an amino acid substitution in the beta subunit of RNA polymerase. Eight mutational changes at seven positions were found in cluster I of the central Rif region. Certain substitutions (His481/Tyr and Asp471/Tyr [S. aureus coordinates]) were present in several mutants. Substitutions Gln468/Arg, His481/Tyr, and Arg484/His, which conferred high-level rifampin resistance, were identical or in the same codon as those described in other bacterial genera, whereas Asp550/Gly has not been reported previously. Substitutions at codon 477 conferred high- or low-level resistance, depending on the nature of the new amino acid. The levels of resistance of in vivo and one-step in vitro mutants carrying identical mutations were similar, suggesting that no other resistance mechanism was present in the clinical isolates. On the basis of these data and the population distribution of more than 4,000 clinical S. aureus isolates, we propose /=8 microg/ml as new breakpoints for the clinical categorization of this species relative to rifampin.

Reemergence of gentamicin-susceptible strains of methicillin-resistant Staphylococcus aureus: roles of an infection control program and changes in aminoglycoside use.

The spread of methicillin-resistant Staphylococcus aureus (MRSA) in our hospital in the 1980s correlated with increasing acquisition of resistance to antibiotics including gentamicin, rifampin, and fluoroquinolones. During the period 1993-1995, there was a major change in clinical MRSA isolates: the percentage of aminoglycoside-resistant MRSA isolates decreased from 75% to 52%, while the proportion of heterogeneous MRSA strains susceptible to gentamicin, rifampin, and tetracycline increased gradually from 4.9% to 27.5%. We used five epidemiological markers (i.e., antibiotyping, phage typing, pulsed-field gel electrophoresis, and restriction analysis of PCR amplified coagulase and protein A genes) to characterize recent isolates. With use of these techniques, we confirmed the persistence of the aminoglycoside-resistant MRSA clone and identified a clone of erythromycin-susceptible strains among the gentamicin-susceptible isolates and found that the remaining strains were diverse. These changes were due to the introduction of various MRSA strains from outside the hospital, while implementation of infection control measures in 1991 could have led to reduced transmission of the aminoglycoside-resistant MRSA strain. Changes in antibiotic prescribing patterns that resulted in reduced selective pressure from gentamicin may have contributed to the spread of gentamicin-susceptible MRSA strains.