Partial characterization of enterocin MR99 from a corn silage isolate of Enterococcus faecalis

SPARO M, CASTRO M, LAVIGNE V, ANDINO J, GUTIERREZ G, FERNÁNDEZ MARISA MARIEL, DE MARZI MC,. MALCHIODI EL, MANGHI M

JOURNAL OF APPLIED MICROBIOLOGY

Año: 2005 p. 1 - 12

1364-5072

Aims: to assess the inhibitory activity on Gram-positive and Gram-negative bacteria of several species of enterococci recovered from a natural corn silage. Methods and Results: the inhibitory activity of strains of Enterococcus faecalis (58), Ent. faecium (35), Ent. gallinarum (3) and Ent. casseliflavus (4) were studied employing indicator strains from various sources (clinical, food and ATCC). Ent. faecalis MR99, the only strain with inhibitory activity, inhibited other enterococci, Listeria spp., Staphylococcus aureus, Clostridium spp., Bacillus spp., Escherichia coli, Shigella sonnei and Sh. flexneri. The bacterium contained only one conjugative pheromone-responsive plasmid. The partially chromatography-purified MR99 enterocin (PPE) had a m.w. of~5 000 Da and a pI of 6.2, was sensitive to proteolytic enzymes and could be extracted in benzene and butanol. It appeared stable to adjustment of pH 4.0, 5.0, 6.0, 7.0 and 8.0 and was resistant 15 min at 121°C. Enterocin MR99 was bactericidal on L. monocytogenes, Staph. aureus, and bovine mastitis agents and it was bacteriostatic on E. coli. PCR studies demonstrated that enterocins MR99 and AS-48 are not related. Conclusions: due to its features, MR99 might be employed as a food preservative and also as an alternative therapeutic means for bovine mastitis. Significance and Impact of Study: the biological properties of the Ent. faecalis MR99 should have beneficial effects at both human and veterinary health levels