Food Safety - Staphylococcus

Testing for Staphylococcus in Food Industries

Staphylococcus are present in the environment and can be found on the skin and upper respiratory tract. Pathogenic species include S. aureus, S. epidermidis, S. saprophyticus, S. intermedius, S. pseudintermedius. The bacteria can mutate and a strain of S. aureus was found to be resistant to the drug methicillin and it is labelled as MRSA. In 1997, a strain of S. aureus was isolated as resistant to vancomycin. Staph aureus is also the cause of mastitis in sheep and cow udders. S. aureus has a high salt tolerance and grow in ham, meat, dairy products, sandwiches, cream filled pastries, chocolates and cold salads. As such it is important to test for this bacteria in ready to eat foods and chocolate. Staph aureus can survive in a dry state but outbreaks are usually due to post processing contamination and or thermal abuse. They have an amazing ability to form biofilms.

Staphylococcus is a spherical non- sporulating, non-motile bacteria and usually occurs in pairs, short chains and grape like clusters. They belong to the family Staphylococcaceae. They are facultative aero anaerobic and are gram positive and catalase positive. S aureus produces an array of toxin that are not destroyed by heat. Some of the toxins are cytolytic and some hemolysins e.g. alpha, beta and delta toxins. They also produce a wide array of enterotoxin and enterolike toxins and emetic toxins. Toxins are usually produced by coagulase positive Staph and seldom by coagulase negative Staph. Existing testing methods do not detect all staph toxins due to its differences.