Effect of Lactococcus garvieae, Lactococcus lactis and Enterococcus faecalis on the behaviour of Staphylococcus aureus in microfiltered milk

The effect of four strains of Lactococcus garvieae, three strains of Lactococcus lactis and one strain of Enterococcus faecalis on Staphylococcus aureus SA15 growth in microfiltered milk was evaluated. Lactococcus and Enterococcus strains were co-cultured with S. aureus in microfiltered milk and in medium buffered at pH 6.8. All Lactococcus and Enterococcus strains were able to inhibit S. aureus growth after 6 h of incubation. Inhibition by L. lactis and E. faecalis strains could be partially attributed to the decrease in pH below 6.0 as it has been observed in medium buffered at pH 6.8. L. garvieae strains were the most effective to inhibit S. aureus growth without acidification. Inhibition of S. aureus could not be attributed neither to production of lactate, acetate or nor to antistaphylococcal substance. Amino acids competition was not involved in the inhibition by L. garvieae as addition of valine, isoleucine, threonine, methionine and phenylalanine did not suppress the inhibition of S. aureus.