Distribution of genes encoding resistance to macrolides, lincosamides, andstreptogramins among staphylococci

The relative frequency of 10 determinants of resistance to macrolides, linc osamides, and streptogramins was investigated by PCR in a series of 294 mac rolide-, lincosamide-, and/or streptogramin-resistant clinical isolates of Staphylococcus aureus and coagulase-negative staphylococci isolated in 1995 from 32 French hospitals. Resistance was mainly due to the presence of erm A or ermC genes, which were detected in 259 strains (88%), in particular th ose resistant to methicillin (78% of the strains). Macrolide resistance due to msrA was more prevalent in coagulase-negative staphylococci (14.6%) tha n in S. aureus (2.1%). Genes related to linA/linA' and conferring resistanc e to lincomycin were detected in one strain of S. aureus and seven strains of coagulase-negative staphylococci. Resistance to pristinamycin and quinup ristin-dalfopristin was phenotypically detected in 10 strains of S. aureus and in three strains of coagulase-negative staphylococci; it was always ass ociated with resistance to type A streptogramins encoded by vat or vatB gen es and occurred in association with erm genes. The vga gene conferring decr eased susceptibility to type A streptogramins was present alone in three st rains of coagulase-negative staphylococci and in combination with erm genes in 10 strains of coagulase-negative staphylococci. A combination of vga-vg b-vat and ermA genes was found in a single strain of S. epidermidis.