Multilocus sequence typing (MLST) shows that the 'Iberian' clone of methicillin-resistant Staphylococcus aureus has spread to France and acquired reduced susceptibility to teicoplanin.

Abstract

Infection by methicillin-resistant Staphylococcus aureus (MRSA) presents a serious problem, as these organisms are resistant to a wide range of antibiotics. Moreover, MRSA with reduced susceptibility to glycopeptides (GISA) have emerged in recent years. In our hospital we were faced with an outbreak of GISA between January and March 2000, involving six patients who were free of MRSA when the GISA isolate emerged, and five of whom had not been given glycopeptides. The initial GISA isolate from the six patients was compared with six 'historical' multiple-resistant MRSA isolates (1996-1999), which had not been found to be GISA by the routinely used method. Antibiotic susceptibility was studied through the disc diffusion method, and MICs of glycopeptides were determined by Etest, agar and broth dilution techniques. Molecular strain typing was done by PFGE and multilocus sequence typing (MLST). All 12 isolates that belonged to the gentamicin-resistant group of MRSA were susceptible to vancomycin, but showed reduced susceptibility to teicoplanin through at least one MIC method. PFGE typing yielded five different but closely related profiles, and eight of the 12 clinical isolates were classified into a single PFGE type. MLST yielded an identical allelic profile for all 12 isolates, corresponding to the profile (3-3-1-12-4-4-16) of the 'Iberian' clone HPV107 of MRSA. MLST allowed us to confirm the presence of the 'Iberian' MRSA clone HPV107 with the same allelic profile in our hospital for several years. We can now note that strains of this clone have acquired reduced susceptibility to teicoplanin.