[Molecular epidemiology of strains of Staphylococcus aureus resistant to methicillin, sensitive to aminoglycosides]

Twenty methicillin-resistant Staphylococcus aureus (MRSA) isolates surprisingly susceptible to all aminoglycosides, macrolides, sulfonamides and tetracycline were recovered from 20 elderly patients (mean age, 77) hospitalized in 4 neighbouring facilities between 1996 and 1998. Molecular typing of the isolates performed by restriction fragment length polymorphism of the coagulase gene (PCR-RFLP) and pulsed-field gel electrophoresis (PFGE) of Sma I macrorestriction fragments of total DNA, demonstrated the existence of distinct bacterial clones. Epidemic spreading was demonstrated for at least 2 clones, while others were responsible for sporadic cases. Most of the isolates of this study appeared to be genetically related to strains of MRSA resistant to aminoglycosides and macrolides included as controls, suggesting that multiresistant MRSA may have evolved recently in a manner that resulted in greater susceptibility to certain antibiotics.