Guarding food safety

Evidence suggests that an estimated 0.1 µg of staphylococcus enterotoxins can cause food poisoning in humans. However, ingestion of less than 200 ng of enterotoxin A is sufficient to cause illness in susceptible individuals. Infectious does (ID), the load of S.aureus required to produce enterotoxin and cause infection in humans is 10^5 –10^8 cfu/g.

According to the Compendium of Microbiological Criteria for Food, FSANZ:

Ready-to-eat foods contaminated with Staphylococcus aureus and other coagulase positive staphylococci are considered potentially hazardous above a microbial limit of 10^4 cfu/g.

S.aureus and its enterotoxin is tested and detected as:

• Catalase positive, coagulase positive, yellow colonies on salt mannitol agar and black colonies with a halo on Baird Parker agar.

• Enterotoxin of S.aureus also can be rapidly detected by a novel method using Staphylococcal Enterotoxin Reversed Passive Latex Agglutination Kit (SET- RPLA).

• Molecular techniques for detection of S.aureus include strand exchange amplification (SEA), polymerase chain reaction (PCR), pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) while Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), western blotting, enzyme-linked immunosorbent assay (ELISA) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) are used to detection of toxin.