Frequency of Genes Encoding Toxic Shock Syndrome and Exfoliative Toxins among Methicillin Resistant Staphylococcus aureus Strains Isolated from Patients in Isfahan. 2017-19

Staphylococcus aureus produces a wide variety of exoproteins that contribute to its ability to colonize and cause disease in mammalian hosts. Nearly all strains secrete a group of enzymes and cytotoxins and some strains produce one or more additional exoproteins, which include toxic shock syndrome toxin-1 (TSST-1), the staphylococcal enterotoxins, the exfoliative toxins (ETA and ETB), and leukocidin. The aim of this study was to determine the frequency of tsst, eta, and etb genes encoding TSST1, ETA and ETB, respectively, among methicillin resistant S. aureus (MRSA) strains isolated from 2 referral hospitals in Isfahan.

During 2017 and 2019 a total of 307 MRSA strains were collected from patients in 2 referral hospitals in Isfahan. All isolates were identified using specific primers for nucA and mecA genes. For typing of bacterial strains, prophage typing using multiplex-PCR was employed and presence of tsst, eta and etb genes was determined using separate PCR assays.

Using PCR by specific primers all bacterial isolates were confirmed as MRSA. Six prophage types SGA (6%), SGB (63%), SGF (100%), SGFa (100%), SGFb (100%) and SGL (6%) and also 4 prophage patterns were identified among strains, in which pattern 3 was the dominant one. Moreover, 63% of strains were positive for both tsst and eta genes and etb gene was not detected among the strains.

The results of the present study indicated the high prevalence of MRSA strains harbored genes encoding TSST-1 and exfoliative toxin in studied hospitals in Isfahan.