Staphylococcal accessory gene regulator (sar) as a signature gene to detect enterotoxigenic staphylococci

To evaluate the use of a staphylococcal accessory gene regulator (sar) as a means of detecting enterotoxigenic staphylococci.

SarA gene-specific primers were designed and applied in PCR, which resulted in the detection of 49 sar-positive isolates from a total of 67 natural food isolates of staphylococci. Colony hybridization using PCR-generated Digoxigenin (DIG)-labelled sarA probe tested in spiked samples of khoa (a traditional heat-concentrated milk product) comprising a mixed microflora ensured the specificity of the probe. Validation experiments with the commercial samples of khoa also demonstrated the specificity of the probe. PCR characterization for enterotoxins A-D revealed the presence of at least one of the toxin-encoding genes in all the sarA-positive isolates tested.

The study indicated that sarA gene could be an ideal marker gene either in colony hybridization or in PCR, for an effective detection of potentially enterotoxigenic strains of staphylococci in a food system.

As an alternative to targeting the individual toxin genes, a regulatory gene responsible for controlling the synthesis of various virulence factors may be a suitable target gene for screening potentially toxigenic staphylococci in food system using nucleic acid-based methods.