CHARACTERIZATION OF A STAPHYLOCOCCAL PLASMID RELATED TO PUB110 AND CARRYING 2 NOVEL GENES, VATC AND VGBB, ENCODING RESISTANCE TO STREPTOGRAMIN-A AND STREPTOGRAMIN-B AND SIMILAR ANTIBIOTICS

We isolated and sequenced a plasmid, named pIP1714 (4,978 bp), which s pecifies resistance to streptogramins A and B and the mixture of these compounds. pIP1714 was isolated from a Staphylococcus cohnii subsp. c ohnii strain found in the environment of a hospital where pristinamyci n was extensively used. Resistance to both compounds and related antib iotics is encoded by two novel, probably cotranscribed genes, (i) vatC , encoding a 212-amino-acid (aa) acetyltransferase that inactivates st reptogramin A and that exhibits 58.2 to 69.8% aa identity with the Vat , VatB, and SatA proteins, and (ii) vgbB, encoding a 295-aa lactonase that inactivates streptcpgramin B and that shows 67% aa identity with the Vgb lactonase. pIP1714 includes a 2,985-bp fragment also found in two rolling-circle replication and mobilizable plasmids, pUB110 and pB C16, from gram-positive bacteria. In all three plasmids, the common fr agment was delimited by two direct repeats of four nucleotides (GGGC) and included (i) putative genes closely related to repB, which encodes a replication protein, and to pre(mob), which encodes a protein requi red for conjugative mobilization and site-specific recombination, and (ii) sequences very similar to the double- and single-strand origins ( dso, sso(U)) and the recombination site, RSA. The antibiotic resistanc e genes repB and pre(mob) carried by each of these plasmids mere found in the same transcriptional orientation.