Anti-Staphylococcal Enterotoxinogenesis of Lactococcus lactis in Algerian Raw Milk Cheese

Staphylococcus aureus is a potential pathogen contaminating raw milk and dairy - products, where it is able to produce thermostable enterotoxins that can cause staphylococcal food poisoning. This study was undertaken to investigate the inhibitory activity of a Lactococcus lactis strain (isolated from milk) on S. aureus growth and staphylococcal enterotoxin A (SEA) production. In the presence of L. lactis, the number of the pathogen decreased significantly (p<0.05) after 6 h of incubation in a laboratory medium and milk (3 log CFU/mL reduction compared to pure cultures). SEA concentration was reduced by 79 % in the co-cultures. S. aureus was unable to reach population levels permitting SEA production in the cheese inoculated with L. lactis during 32 days of storage. In contrast, during the same period, it attained 7 log CFU/g in the cheese manufactured without the lactococcal strain, a level which permitted SEA detection in the cheese extracts. However, this enterotoxin was never detected in the cheese harbouring L. lactis. These results demonstrate the anti-staphylococcal enterotoxinogenesis potential of the L. lactis strain and its usefulness in raw milk cheese biopreservation.