Sequences found on staphylococcal beta-lactamase plasmids integrated into the chromosome of Enterococcus faecalis CH116

Abstract

We have previously reported the presence of the staphylococcal beta-lactamase gene in chromosomes of Enterococcus faecalis strains CH19 and CH116. CH116 also harbors a 26-kb mobile element, designated Tn5384, which confers resistance to erythromycin and gentamicin. Sequence analysis of the rightmost 9 kb of Tn5384 indicates that this element lies immediately upstream of the beta-lactamase determinant in E. faecalis CH116. This 9-kb region consists of sequences highly homologous to those previously described in staphylococcal beta-lactamase plasmids, including a beta-lactamase transposon indistinguishable from Tn552, an open reading frame encoding a deduced amino acid sequence 94% identical to a previously described potential staphylococcal invertase, an intact copy of staphylococcal insertion-like element IS257, and the major portion of the staphylococcal organomercurial lyase (merB) gene. These data are consistent with the hypothesis that several of the resistance genes encoded within the large transferable region of the CH116 chromosome were originally components of a staphylococcal beta-lactamase plasmid.