IDENTIFICATION OF THE SATA GENE ENCODING A STREPTOGRAMIN-A ACETYLTRANSFERASE IN ENTEROCOCCUS-FAECIUM BM4145

Enterococcus faecium BM4145, a clinical isolate from urine, was resist ant to streptogramin group A antibiotics by inactivation. The strain h arbored a plasmid containing a gene, satA, responsible for this resist ance; this gene was cloned and sequenced. It encoded SatA, a protein d educed to be 23,634 Da in mass and homologous with a new family of chl oramphenicol acetyltransferases described in Agrobacterium tumefaciens , Escherichia coli, Pseudomonas aeruginosa, and Staphyloccus aureus. T he similarity of SatA to other acetyltransferases, LacA (thiogalactosi de acetyltransferase) and (serine acetyltransferase; from E. coli, and to two putative acetyltransferases, NodL from Rhiobium leguminosarum and Urf1 from E. coli, was also observed in a region considered to be the enzyme's active site. Acetylation experiments indicated that acety l coenzyme A was necessary for SatA activity and that a single acetyla ted derivative of pristinamycin IIA was produced. Other members of the streptogramin A group such as virginiamycin M and RP54476 were also s ubstrates for the enzyme. We conclude that resistance to the streptogr amin A group of antibiotics in E. faecium BM4145 is due to acetylation by an enzyme related to the novel chloramphenicol acetyltransferase f amily.