Inhibition of Staphylococcus aureus in dairy products by enterocin AS-48 produced in situ and ex situ: Bactericidal synergism with heat

The efficacy of enterocin AS-48 to control Staphylococcus aureus in skimmed milk and in fresh cheese has been assayed. In milk, added AS-48 inhibited S. aureus in a concentration-dependent mode. Bacteriocinogenic strain Enterococcus faecalis A-48-32 produced high amounts of AS-48 in milk (18–20 mm inhibition zones) and controlled S. aureus when co-cultivated at different enterococci/staphylococci ratios (approximately 100/1, 1/1, and 1/100). AS-48, produced ex situ or in situ, in combination with moderate heat treatment (65 °C, 5 min), had a strong anti-staphylococci synergistic effect, with a concentration of 20 μg mL−1 being sufficient to eliminate staphylococci after 6-h incubation. The efficacy of bacteriocinogenic strains, E. faecalis A-48-32 and E. faecium UJA32-81, was lower in unripened cheese, but staphylococci counts in treated cheeses remained at least 1 log cfu g−1 below controls throughout storage. Highest inhibition (4–2 log cfu g−1 below controls) was obtained within the first storage week.