Molecular characterization of the vanE gene cluster in vancomycin-resistant Enterococcus faecalis N00-410 isolated in Canada

Abstract

The vanE operon was characterized from Enterococcus faecalis N00-410 (MIC of vancomycin = 24 microg/ml). The organization of the vanE operon was identical to that of the vanC1 operon from Enterococcus gallinarum, with protein identities ranging from 46 to 63%. An open reading frame located downstream of the vanE operon showed significant homology to a number of integrase genes, all of which are located downstream of the chromosomal GMP synthase gene guaA.

FIG. 1.

Genetic organization of the vanE locus from E. faecalis N00-410 showing regions cloned into plasmids and regions isolated by inverse PCR and PCR. The direction of transcription is indicated by arrows, and putative stem-loop structures are indicated. Primers used in inverse PCR and PCR are indicated by black arrowheads: primer 1 is vanRE-1, primer 2 is vanSE-DN1, primer 3 is Eint-DN1, and primer 4 is gua-DN1. The organization of the vanC1 locus from E. gallinarum is shown at the top. Percent identities of the corresponding vanC1 and vanE operon proteins are shown. RV indicates EcoRV sites.

FIG. 2.

Alignments of the int-guaA intergenic regions from S. aureus Mu50 (SaMu50), E. faecalis N00-410 (EfN410), and E. faecalis V583 (EfV583). The sequence from the equivalent region in C. perfringens CW459 is identical to that of S. aureus Mu50. Asterisks indicate an identical nucleotide in all three sequences, and periods indicate an identical nucleotide in two out of three sequences. The ΔG values of the inverted repeats are indicated after each sequence. DR, direct repeat; IR, inverted repeat.