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

SPARO MD, CASTRO MS, ANDINO PJ, LAVIGNE MV, CERIANI C; GUTIÉRREZ GL, FERNÁNDEZ MM, DE MARZI MC, MALCHIODI EL & MANGHI MA.

APPLIED MICROBIOLOGY AND BIOTECHNOLOGY

SPRINGER

Año: 2006 vol. 68 p. 747 - 752

0175-7598

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. Even though enterocins MR99 and AS48 have inhibitory activity on Gram-negative bacilli, PCR studies demonstrated a lack of relationship between them. Conclusions: the active component had a protein  nature, was resistant to heat and presented a wide inhibitory spectrum. Significance and Impact of Study: the biological properties of Ent. faecalis MR99 suggest that this strain merits further investigations so it can be applied in human and veterinary health programs.