Development of a multiplex polymerase chain reaction assay for detection and differentiation of Staphylococcus aureus in dairy products

A multiplex polymerase chain reaction (PCR) assay was developed for the det ection and differentiation of enterotoxigenic Staphylococcus aureus in dair y products. A solvent extraction procedure was successfully modified for ex traction of S. aureus DNA from 10 ml of artificially contaminated skim milk or 20 g cheddar cheese. Primers targeting the enterotoxin C gene (entC) an d thermostable nuclease gene (nuc) were used in the multiplex PCR. PCR prod ucts were confirmed using restriction fragment length polymorphism analysis . DNA was consistently quantified and amplified by uniplex PCR from 10 CFU/ ml of S. aureus in skim milk or 10 CFU/20 g cheddar cheese. The sensitivity of the multiplex PCR was 100 CFU/ml of skim milk or 100 CFU/20 g cheddar c heese. The developed methodology allows presumptive identification and diff erentiation of enterotoxigenic S. aureus in less than 6 h.