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Appl. Environ. Microbiol. doi:10.1128/AEM.00934-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Genetic analysis of bacteriocin 43 (Bac 43) of vancomycin-resistant Enterococcus faecium

Department of Bacteriology and Bacterial Infection Control, Department of Ophthalmology and Laboratory of Bacterial Drug Resistance, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan

^* To whom correspondence should be addressed. Email: tomitaha{at}med.gunma-u.ac.jp,

	Abstract

A total of 636 vancomycin-resistant Enterococcus faecium (VRE) isolates that had been obtained between 1994 and 1999 from the Medical School Hospital of the University of Michigan, were tested for bacteriocin production. Of the 277 (44%) bacteriocinogenic strains, 21 were active against E. faecalis, E. faecium, E. hirae, E. durans and Listeria monocytogenes. Of the 21 strains, a representative bacteriocin of strain VRE82, designated bacteriocin 43, was found to be encoded on the mobilizable plasmid pDT1 (6.2 kbp). Nine ORFs from ORF1 to ORF9 were presented on pDT1 and were orientated in the same direction. The bacteriocin 43 locus (bac43) consists of the bacteriocin gene bacA (ORF1) and the immunity gene bacB (ORF2). The deduced bacA product is 74 amino acids in length with a putative signal peptide of 30 amino acids at the N-terminus. The bacB gene encodes a deduced 95 amino acid protein without a signal sequence. The predicted mature BacA protein (44 amino acids) showed sequence homology with the membrane-active class II bacteriocins of lactic acid bacteria, and showed 86% residue homology with bacteriocin 31 from E. faecalis YI717, and 98% residue homology with bacteriocin RC714. Southern analysis using a bac43 probe of each plasmid DNA from the 21 strains showed hybridization to a specific fragment corresponding to the 6.2 kbp EcoRI fragment, suggesting that the strains harbored the pDT1-like plasmid (6.2 kb) which encoded Bac 43-type bacteriocin. The bac43 gene was not identified among non-VRE clinical isolates.