Survey of accessory gene regulator (agr) groups and TSST-1 encoding gene (tst) in Staphylococcus aureus isolated from ewes with mastitis in the northwest of Iran

Document Type : Full paper (Original article)


1 Department of Microbiology, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran

2 Graduated from Faculty of Veterinary Medicine, Urmia University, Urmia, Iran


Accessory gene regulator (agr locus) is a global regulator of many virulence gene expressions in
Staphylococcus aureus. Four interference classes related to genetic polymorphisms in the agr locus have so
far been described. In the present study, the agr locus specificity groups were studied within a total of 43 S.
aureus isolates which were isolated from ewes with mastitis in three regions in the Northwest of Iran. In
addition, the isolates were examined for the presence of TSST-1 (toxic shock syndrome toxin-1) encoding
gene (tst) using PCR. Identification of agr groups, using agr group-specific multiplex PCR, classified the
majority of isolates into group I (51.16%) and to a lesser extent into agr group IV (44.19%). Only one isolate (2.23%) for each of the agr groups II and III was found. This study also indicated that 44.19% of isolates (n=19) possessed the tst gene and that 94.74% (n=18) belonged to agr group I. According to the results, certain agr groups comprised the great majority of sheep mastitis associated S. aureus isolates. Moreover, the high proportion of S. aureus isolates was tst positive, indicating an issue requiring consideration as it is relevant to food hygiene. The results also showed a variation in distribution of the tst gene among the different agr groups.