Bacteriocin production was determined for 218 Enterococcus isolates (Enterococcus faecalis [93] and E. faecium
[125]) obtained from different origins (human clinical samples [87], human fecal samples [78], sewage [28],
and chicken samples [25]) and showing different vancomycin susceptibility patterns (vancomycin resistant, all
of them vanA positive [56], and vancomycin susceptible [162]). All enterococcal isolates were randomly selected
except for the vancomycin-resistant ones. A total of 33 isolates of eight different bacterial genera were
used as indicators for bacteriocin production. Forty-seven percent of the analyzed enterococcal isolates were
bacteriocin producers (80.6% of E. faecalis and 21.6% of E. faecium isolates). The percentage of bacteriocin
producers was higher among human clinical isolates (63.2%, 81.8% of vancomycin-resistant isolates and 60.5%
of vancomycin-susceptible ones) than among isolates from the other origins (28 to 39.3%). Only one out of the
15 vancomycin-resistant isolates from human fecal samples was a bacteriocin producer, while 44.4% of fecal
vancomycin-susceptible isolates were. The bacteriocin produced by the vanA-containing E. faecium strain RC714,
named bacteriocin RC714, was further characterized. This bacteriocin activity was cotransferred together with
the vanA genetic determinant to E. faecalis strain JH2-2. Bacteriocin RC714 was purified to homogeneity and
its primary structure was determined by amino acid sequencing, showing an identity of 88% and a similarity of
92% with the previously described bacteriocin 31 from E. faecalis YI717. The presence of five different amino acids
in bacteriocin RC714 suggest that this could be a new bacteriocin. The results obtained suggest that the epidemiology
of vancomycin resistance may be influenced by different factors, including bacteriocin production.
R. D. C. was supported by a grant from the Diputación General de
Aragón of Spain (project P49/97) and from the Sociedad Española de
Quimioterapia. This work has been supported in part by a grant from
the Fondo de Investigaciones Sanitarias (00/0545) of Spain.
Peer reviewed