Production of antagonistic compounds was studied in a strain of Enterococcus faecium isolated from the intestinal tract of a free-ranging chicken. Production of lactic acid and a bacteriocin was observed in cultures of this bacterium, alone and in mixed culture fermentations with pathogenic Salmonella serotypes (i.e., Gallinarum, Pullorum, Enteritidis, and Typhimurium). Growth inhibition of these avian and human pathogens was observed after 4 h of incubation at 37°C in CAm broth, a medium developed according to the nutrients present in chicken food. The antibacterial action was due to the combined effect of lactic acid and bacteriocin. Accumulation of these metabolites caused both a bacteriostatic and a bactericidal action against the gram-negative bacteria assayed.

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