[Resistance to pristinamycin (or virginiamycin) of strains of Staphylococcus aureus].

Resistance to pristinamycin (or virginiamycin) was first encountered in Staphylococcus aureus strains in 1975. These strains are usually multiresistant, in particular to streptogramin A components (SgA), macrolides, lincosamides and streptogramin B components (ML SgB ). Results of molecular analysis of 16 such strains, recently isolated, suggests that SgA resistance is not encoded by plasmid genes. Curing and mixed culture experiments allowed us to dissociate SgA from SgB resistance genes. Conversely, in a previous study on other strains, the same two resistance genes were shown to be carried by a single plasmid and could not be dissociated. Since 1981, a new type of pristinamycin -resistant S. aureus strains has been isolated. These strains are resistant to SgA and lincosamides but susceptible to macrolides and SgB . Eight such strains from 3 parisian hospitals have been studied. In mixed culture experiments, SgA resistance and penicillinase genes always transferred jointly. In some instances, these two determinants also cotransferred with genes encoding lincomycin, lincomycin and clindamycin, and/or aminoglycosides resistance.