Biotyping and enterotoxigenicity of coagulase-positive and coagulase-negative staphylococci isolated from different raw meat

Staphylococcal enterotoxins (SEs) are produced in foods under favorable conditions and considered a potential biological threat.

The study was performed to detect enterotoxigenic genes of A and B in coagulase-positive (CPS) and coagulase-negative staphylococci (CNS) to evaluate biotypes and antibiotic resistance of isolated Staphylococcus aureus from different meat.

A total of 160 meat swab samples were collected from lamb, water buffalo, cattle, and chicken carcasses. Presumptive colonies on Baird Parker agar were subjected to biochemical identification, including Gram staining, catalase, oxidase, and coagulase activity. Relevant colonies separately were subjected to the polymerase chain reaction (PCR) assay for identification of Staphylococcus genus, enterotoxigenic genes (sea and seb) and the thermonuclease gene (nuc) specific for the S. aureus. The antibiotic susceptibility test was also carried out using five antibiotics.

Totally, 150 Staphylococcus spp. were isolated from the samples among which 135 (90%) isolates harbored sea gene, meanwhile, none of the isolates contained seb gene. Twenty-five S. aureus confirmed by PCR from which 15 isolates (60%) belonged to host specific (HS), 7 isolates (28%) belonged to non-host specific (NHS) biotypes, while 3 isolates (12%) were non-typable. Overall, 68%, 56%, 16%, 12%, and 8% of isolates were resistant to penicillin, trimethoprim, gentamicin, oxacillin, and erythromycin, respectively.

The meats provided from this area were contaminated with enterotoxigenic and antibiotic-resistance staphylococci, which can threaten the health of the consumers. The study showed that not only CPS contain enterotoxin A gene, but also CNS isolates possess this gene, especially in buffalo meat, and thus they are recognized as potential hazards in different meats.