Linkage of determinants for streptogramin A, macrolide-lincosamide-streptogramin B, and chloramphenicol resistance on a conjugative plasmid in Enterococcus faecium and dissemination of this cluster among streptogramin-resistant enterococci

A new streptogramin A resistance gene, satG (= vatE), has been recently ide ntified in Enterococcus faecium UW1965 (Werner and Witte 1999. Antimicrob. Agents Chemother. 43: 1813-1814). Further sequence analysis of this plasmid revealed that vatE is in a cluster together with other resistance genes. T he identified ORFs were nearly identical with the already known genes ermB and cat. The ermB fragment exhibited more than 99 % identity with a resista nce region from the streptococcal plasmid pIP501, whereas the cat fragment also contained a truncated rep gene homologue with more than 99 % identity to sequences in small staphylococcal plasmids. The cat-rep and the ermB-vat E segments were linked by an IS1216V insertion sequence widely distributed among enterococci. PCR analysis of additional 76 streptogramin-resistant is olates possessing vatE and ermB revealed a linkage of both genes in 45 isol ates (59 %); 25 of them with a gene arrangement, cat-repU-IS1216V-ermB-vatE identical to the reference strain UW1965. An identical linkage of IS1216V- ermB-vatE was found among isolates from poultry manure, poultry meat, stool samples of humans, and hospital patients indicating a possible spread of t he resistance gene cluster via the food chain to humans.