Analysis of the bacteriocins of vancomycin-resistant Enterococcus faecium (VRE) clinical isolates

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A total of 636 VRE isolates obtained from the Medical School Hospital of the University of Michigan were tested for bacteriocin production. Two hundred seventy-seven (44%) of the strains were bacteriocinogenic. Two bacteriocin plasmids pTI1(12.5 kb) and pDT1 (6.2 kb) were isolated from the strains VRE200 and VRE82, respectively. pTI1 encoded bacteriocin 32 (Bac 32) active against E.faecium, E. hirae and E. durans. pDT1 encoded bacteriocin 43 (Bac 43) active against E.faecalis, E.faecium, E.hirae, E.durance and Listeria monocytogenes. Bact 32 gene consists of the bacteriocin gene bacA and the immunity gene bacB. The deduced bacA product is 89 amino acids in length, with a putative signal peptide of 19 amino acids at the N terminus. Bac 32 showed no homology to any known bacteriocin determinant. Bac 43 gene consists of the bacteriocin gene bacA and the immunity gene bacB. The deduced bacA product of Bac 43 is 74 amino acids in length with putative signal peptide of 30 amino acids at the N terminus. Bac 43 showed the high homologies with the membrane-active class IIa bacteriocins of lactic acid bacteria. Southern analyses and PCR amplification analyses showed that among the 277 bacteriocinogenic strains 137 isolates (49.5 %) carried the bac 32 gene and 22 isolates (7.9 %) carried the bac 43 gene, respectively.