Survival of acid-adapted and non-adapted Staphylococcus aureus in various food samples

Abstract

Resistance of Staphylococcus aureus to acid pH was studied. Staphylococcus aureus ATCC 6538 was acid-adapted at pH 5.0 in tryptic soy broth (TSB) for 4 h. Commercial products, mayonnaise pH 3.57, rape pH 3.72, fatty yogurt pH 4.01, were purchased from a local supermarket, and kisir köfte pH 4.9 samples were prepared by us. All of the samples were inoculated with acid-adapted or non-adapted cells of S. aureus. In un-inoculated mayonnaise, rape, fatty yogurt, and kisir köfte S. aureus was not detected. The viable population of S. aureus in mayonnaise declined quickly when stored at 4 or 25 °C. After 48 h of storage, no viable cells were recovered from mayonnaise inoculated with acid-adapted or non-adapted ATCC 6538 at 25 °C. Acid-adapted cells were recovered in greater numbers than non-adapted cells during storage at 4 or 25 °C. After 24 h of storage, no viable cells were recovered from rape and yogurt inoculated with acid-adapted and non-adapted ATCC 6538 at 4 and 25 °C. Acid-adapted S. aureus survived in kisir köfte during 48 h. After 72 h of storage, no viable cells were recovered from kisir köfte inoculated with acid-adapted and non-adapted ATCC 6538 at 25 °C and 4 °C.