Identification of Staphylococcus aureus cheese isolates with respect to virulence properties, genetic relatedness and antibiotic resistance profiles

Abstract

The problems on identification of Staphylococcus aureus isolates from cheese samples wereinvestigated by phenotypic and genotypic tests in this study. Among 207 Staphylococcus spp.isolated from 31 cheese samples, 23 isolates that were Gram positive, catalase and slide coagulasepositive, with 1 isolate that was latex agglutination test negative showed different phenotypicproperties. Polymerase chain reaction (PCR) and quantitative PCR (qPCR) analyses showed thatDNase test and target genes (nuc, coa) regarded as gold standard regions for S. aureus were notfound to be unique for identification of S. aureus. The toxin genes (SEA-SEE) were not detected byPCR. Antibiotic resistance profiles of S. aureus isolates demonstrated that two isolates were resistantto penicillin G. This study showed that the unique phenotypic and genotypic test was not adequatefor identification of S. aureus isolates. There was no correlation between the presence of the nucgene and toxin genes. The presence of nuc gene which was used for detection of S. aureus was alsofound to be present in other Staphylococcus isolates. As a conclusion, the results revealed thatbiochemical tests could lead to false positive results for identification of S. aureus. The presence ofnuc gene is not correlated with the presence of toxin genes.