Phenotypic and Molecular Typing of Nosocomial Methicillin-Resistant Staphylococcus aureus Strains Susceptible to Gentamicin Isolated in France from 1995 to 1997

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FONTE

American Society for Microbiology

RESUMO

Methicillin-resistant strains susceptible to gentamicin (Gms MRSA) have emerged since 1993 in several French hospitals. To study whether particular clones have spread in various French cities and whether some clones are related to gentamicin-resistant (Gmr) MRSA strains, various methods (antibiotyping, phage typing, determination of SmaI macrorestriction patterns before and after hybridization with IS256 transposase and aacA-aphD probes) were used to compare 62 Gms MRSA strains isolated from 1995 to 1997 in nine cities and 15 Gmr MRSA strains. Eighteen major SmaI genotypes were identified, of which 11 included only Gms MRSA strains and 5 included only Gmr MRSA strains. Each of the Gmr MRSA strains contained 6 to 13 SmaI fragments hybridizing with the insertion sequence IS256, of which a single band also hybridized with the aacA-aphD gene. No such hybridizing sequences were detected in 60 of the 62 Gms MRSA strains. Thus, the divergence between Gmr and Gms MRSA strains is revealed, not only by their distributions in distinct SmaI genotypes but also by the differences in hybridization patterns. Two of the 62 Gms MRSA strains had the uncommon feature of carrying several SmaI bands hybridizing with IS256, suggesting that they are possibly related to the Gmr MRSA strains grouped in the same SmaI genotype. Five of the 11 SmaI genotypes including only Gms MRSA strains contained strains from diverse cities, isolated during different years and with different antibiograms, suggesting that some clones have spread beyond their cities of origin and persisted.

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