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

SPARO MD, CASTRO MS, ANDINO PJ, LAVIGNE MV, CERIANI C, GUTIERREZ GL, FERNANDEZ M, DE MARZI M, MALCHIODI E, MANGHI M

JOURNAL OF APPLIED MICROBIOLOGY

Published for the Society for Applied Bacteriology by Blackwell Science

Lugar: England; Año: 2006 vol. 100 p. 123 - 134

1364-5072

AIMS: To assess the inhibitory activity on Gram-positive and Gram-negativebacteria of several species of enterococci recovered from a natural corn silage.METHODS AND RESULTS: The inhibitory activity of strains of Enterococcus faecalis(58), Enterococcus faecium (35), Enterococcus gallinarum (3) and Enterococcuscasseliflavus (4) were studied employing indicator strains from various sources(clinical, food and ATCC). Enterococcus faecalis MR99, the only strain withinhibitory activity, inhibited other enterococci, Listeria spp., Staphylococcusaureus, Clostridium spp., Bacillus spp., Escherichia coli, Shigella sonnei andShigella flexneri. The bacterium contained only one conjugativepheromone-responsive plasmid. The partially chromatography-purified MR99enterocin (PPE) had a molecular weight of approx. 5000 Da and a pI of 6.2, wassensitive 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 wasresistant to heat. Inactivation was at 15 min at 121 degrees C. Enterocin MR99was bactericidal on strains of Listeria monocytogenes, Staph. aureus, and bovinemastitis agents, it was bacteriostatic on E. coli. Although enterocins MR99 andAS48 have inhibitory activity on Gram-negative bacilli, PCR studies demonstrateda lack of relationship between them. CONCLUSIONS: The active component had aprotein nature, was resistant to heat and presented a wide inhibitory spectrum.SIGNIFICANCE AND IMPACT OF THE STUDY: The biological properties of Ent. faecalisMR99 suggest that this strain merits further investigations so it can be appliedin human and veterinary health programmes.