Appearance of methicillin-resistant Staphylococcus aureus (MRSA) sensitive to gentamicin in a hospital with a previous endemic distinct MRSA.

Since 1990 a clone of gentamicin and methicillin-resistant Staphylococcus aureus (MRSA) has remained endemic in our hospital, but since January 1996 a gentamicin-sensitive strain has progressively replaced the previous clone. We characterized the phenotypic and molecular pattern of the MRSA strains isolated in our hospital in 1996 and compared prospectively the epidemiological, clinical and evolutionary characteristics of ninety patients infected or colonized by gentamicin-sensitive MRSA (GS-MRSA) (49) and by gentamicin-resistant MRSA (GR-MRSA) (41). Finally we studied the variation of aminoglycoside consumption in our hospital from 1989 to 1996. We observed two antibiotypes (GS-MRSA and GR-MRSA) corresponding to two major chromosomal patterns. Patients with GS-MRSA usually acquired the infection 72 hours after hospital admission. No significant differences were observed in epidemiological characteristics, clinical presentation and evolution between patients with GS-MRSA and GR-MRSA. Since 1989 aminoglycoside intake in our hospital has decreased by 46%.