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 mug ml(-1) at 37degreesC to 10 mug ml(-1) at 15degreesC. Sublethally injured cells showed an increased sensitivity with a MBC of 5 mug ml(-1). In this way, the highest effectiveness of Ent AS-48 against S. aureus CECT 976 was obtained at 4degreesC 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.