DIVERSITY AMONG THE GRAM-POSITIVE ACETYLTRANSFERASES INACTIVATING STREPTOGRAMIN A AND STRUCTURALLY RELATED-COMPOUNDS AND CHARACTERIZATION OF A NEW STAPHYLOCOCCAL DETERMINANT, VATB

A gene encoding an acetyltransferase inactivating streptogramin A (SgA ) and structurally similar compounds was isolated from a staphylococca l plasmid and sequenced. This gene, designated vatB, potentially encod es a 212-amino-acid protein, VatB, of 23,320 Da with 47.4 and 58.4% am ino acid identities with two other enzymes with the same activity, Vat and SatA, respectively, which are encoded by a staphylococcal plasmid and an enterococcal plasmid, respectively. The C-terminal parts of th ese three enzymes share significant homology with the C-terminal parts of 10 other acetyltransferases modifying various substrates. A pair o f degenerate primers representing the conserved motifs shared by VatB, Vat, and SatA was designed to detect the three genes encoding these S gA acetyltransferases. Five of 12 clinical SgA(r) Staphylococcus aureu s isolates tested carried neither these genes nor the gene vga, which confers resistance to SgA by a different mechanism, suggesting that an other gene(s) and possibly another mechanism of resistance to SgA in s taphylococci remains to be characterized.