Characterization of a Staphylococcal Plasmid Related to pUB110 and Carrying Two Novel Genes, vatC and vgbB , Encoding Resistance to Streptogramins A and B and Similar Antibiotics

Abstract

ABSTRACT We isolated and sequenced a plasmid, named pIP1714 (4,978 bp), which specifies resistance to streptogramins A and B and the mixture of these compounds. pIP1714 was isolated from a Staphylococcus cohnii subsp. cohnii strain found in the environment of a hospital where pristinamycin was extensively used. Resistance to both compounds and related antibiotics is encoded by two novel, probably cotranscribed genes, (i) vatC , encoding a 212-amino-acid (aa) acetyltransferase that inactivates streptogramin 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 streptogramin 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 pBC16, from gram-positive bacteria. In all three plasmids, the common fragment 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 required 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, RS A . The antibiotic resistance genes repB and pre ( mob ) carried by each of these plasmids were found in the same transcriptional orientation.