Determination of ecovars, antibiotic susceptibility and tst gene frequency in Staphylococcus aureus isolated from dairy food products

S. aureus is a major cause of food borne diseases throughout the world. The aim of the present study was the identification of source contamination and tst gene in Staphylococcus aureus isolated from food of animal origin in Hamedan city. In this study, the contamination sources of 65 S. aureus isolates which had previously been isolated from cream pastry (45 isolates) and traditional Iranian white cheese (20 isolates) were evaluated using biotyping method. Meanwhile, the identification of tst gene by PCR method and susceptibility of the isolates against several antibiotics was examined using standard disk diffusion test. Of the 65 biotyped isolate, 52.3% (34 isolate) and 44.6% (29 isolate) belonged to the host specific (HS) and non-host specific (NHS) biotypes, respectively, and 3.1% isolates (2 isolates) were not placed in in certain types. Besides, human ecovars in cream pastry and bovine ecovars in cheese sample were predominant. The prevalence rate of tst gene in the isolates is 4.6% (3 isolate), and according to the results of antimicrobial susceptibility testing, HS biotypes showed higher resistance than NHS biotypes.

Due to the abundance of human and bovine ecovars in cream pastry and cheese, respectively, it maybe the contamination of cream pastry by human and cheese by bovine have occurred. Also, because of high antibiotic resistance and existence of tst gene among HS biotypes and the possibility of their circulation in the community can have a potentially alarming effect on general health of community.