A PLASMID THAT ENCODES 3 GENES FOR RESISTANCE TO MACROLIDE ANTIBIOTICS IN STAPHYLOCOCCUS-AUREUS

In previous letters, FEMS Microbiol. Lett, 148 (1997) 91-96, it was de monstrated that plasmid pMS97 - obtained from a in 1971 clinically iso lated Staphylococcus aureus strain MS8968 resistant to macrolide (Mac) antibiotics - carried an msrA gene and uncharacterized erm gene, resp ectively, msrA encodes a cytoplasmic membrane protein that mediates th e so-called 'active Mac-efflux' (designated hereafter as msrSA') and e rm encodes a methyltransferase by which a specific adenine residue of 23S rRNA is modified: methylation prevents Mac antibiotics from bindin g to the 50S ribosomal subunit. Interestingly, we found, in addition, an mph-like gene (hereafter referred to as mphBM) present together wit h msrSA' and erm on pMS97, By a BLASTP analysis, the gene mphBM produc t has 49% identity and 67% similarity to the amino acid sequence of MP H(2')II encoded by mphB from Escherichia coli. The order of genes was 5'-msrSA'-mphBM-3', with a 342-base-pair spacer sequence. Although we have not yet determined where erm gene is located on pMS97, the gene s eems to be downstream from mphBM. This finding suggests a warning to u s concerning the imprudent use of antibiotics. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.