Journal Article

A 1 year surveillance study of glycopeptide-intermediate <i>Staphylococcus aureus</i> strains in a French hospital

Fabien Garnier, Delphine Chainier, Timothy Walsh, Asa Karlsson, Anne Bolmström, Carole Grelaud, Marcelle Mounier, François Denis and Marie-Cécile Ploy

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 57, issue 1, pages 146-149
Published in print January 2006 | ISSN: 0305-7453
Published online November 2005 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dki413
A 1 year surveillance study of glycopeptide-intermediate Staphylococcus aureus strains in a French hospital

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Objectives: Glycopeptides are the drugs of choice to treat infections due to methicillin-resistant Staphylococcus aureus, but since 1995, glycopeptide-intermediate S. aureus (GISA) and heterogeneous GISA (hGISA) have been reported worldwide. Detection of reduced susceptibility to glycopeptides in S. aureus is very difficult in a routine clinical laboratory. The aim of this study was to investigate the prevalence of hGISA/GISA strains using a three-step approach during a 1 year period.

Methods: The following algorithm was adopted: (i) brain heart infusion agar with 4 mg/L teicoplanin was used to screen S. aureus strains for reduced susceptibility to glycopeptides; (ii) for each agar screen-positive strain, an Etest macromethod using modified cut-off values (vancomycin and teicoplanin ≥4 mg/L) was used to detect potential hGISA/GISA; and (iii) the population analysis profile (PAP) method was finally used to confirm the hGISA/GISA phenotype.

Results: In total, 2300 strains of S. aureus were screened and 255 (11%) were categorized as hGISA with the PAP method, whereas no GISA strains were detected. Standard MIC values and current MIC breakpoints could not discriminate the hGISA/GISA phenotype from glycopeptide-susceptible S. aureus. Thus laboratories using currently standardized MIC methods cannot be expected to detect S. aureus strains that may exhibit reduced susceptibility to glycopeptides. Molecular typing by PFGE revealed that 238 strains belonged to the same clone.

Conclusions: A clonal hGISA strain has disseminated within our hospital. The method described in this study has to be further investigated to see if it is applicable to other S. aureus strains.

Keywords: glycopeptide resistance; S. aureus; Etest macromethod; population analysis profile method

Journal Article.  1969 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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