Effect of combined physico-chemical preservatives on enterocin AS-48 activity against the enterotoxigenic Staphylococcus aureus CECT 976 strain.

AIMS Control of the enterotoxigenic Staphylococcus aureus CECT 976 strain by enterocin AS-48 in laboratory cultures, and behaviour of the AS-48 activity in the presence of food preservatives. METHODS AND RESULTS Enterocin AS-48 shows inhibitory activity on the majority of the Staphylococcus species tested. This enterocin has a bactericidal and bacteriolytic mode of action on S. aureus CECT 976, a strain selected for this study by its enterotoxigenic character (SEA production). The inhibitory effect of AS-48 was pH and temperature dependent, and enterocin activity was higher at pH 5. The minimum bactericidal concentration (MBC) of AS-48, decreased from 15 microg ml(-1) at 37 degrees C to 10 microg ml(-1) at 15 degrees C. Sublethally injured cells showed an increased sensitivity with a MBC of 5 microg ml(-1). In this way, the highest effectiveness of Ent AS-48 against S. aureus CECT 976 was obtained at 4 degrees C in combination with high concentrations of NaCl (6 and 7%). Interestingly, enterotoxin SEA production by strain CECT 976 was markedly inhibited by subinhibitory concentrations of Ent AS-48. These low concentrations also provoked a delay of bacterial growth. CONCLUSION The results presented indicated that Ent AS-48 has a potential for application as a protective agent against S. aureus in foods. SIGNIFICANCE AND IMPACT OF THE STUDY In this study, we have established the conditions for an efficient inhibition of growth and enterotoxin production by S. aureus CECT 976 in culture media by a combination of environmental factors and Ent AS-48.