Occurrence and molecular characterization of Staphylococcus aureus strains isolated from meat and dairy products by PCR-RFLP
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A total of 100 Staphylococcus aureus strains were isolated from 1,047 food samples. In addition to biotyping all isolates, the occurrence of the tst gene and protein were evaluated by PCR and the RPLA test, respectively. Moreover, polymorphism of the X-region of the protein A gene was analyzed by PCR-RFLP. TSST1 was detected in 12 strains and production of TSST1 in all strains was confirmed by RPLA assay. It was noteworthy that 66.7% of TSST1-producing S. aureus strains belonged to the human biotype. The result of genotyping amplification of the spa gene displayed size polymorphisms and revealed seven different clusters ranging from 1,200 bp to 1,600 bp. Digestion of amplicons with HindIII and HaeII resulted in six distinct patterns for each of them. An amplicon of 1,450 bp in size was the predominant type of Spa-PCR product. The accuracy of the Spa typing system by PCR-RFLP was 100%, thus confirming this method as a reliable tool in routine epidemiological investigation for S. aureus.
KeywordsStaphylococcus aureus Food Molecular typing tsst1 Biotyping
We would like to thank S. Agha Amin for kindly helping in samples collection; A. Azimian (PhD student of microbiology, Isfahan University of Medical Science) for preparing reference strains; I. Ashrafi (Bacteriology Laboratory of the Veterinary Medicine Faculty, Tehran University of Medical Science) for kindly helping with biotyping, and M. Shokuhi (Physiology Research Centre, Kerman University of Medical Science) for helping us with data analysis.
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