Incidence of Oxacillin-Susceptible mecA-Positive Staphylococcus aureus (OS-MRSA) Isolates and TSST-1 Virulence Factor Among High School Students in Tabriz, Northwest of Iran

Methicillin-resistant Staphylococcus aureus (MRSA) is often the cause of a wide broad of infections ranging fromminor skin infections to serious infections such as toxic shock syndrome (TSS) in hospital and community settings. Toxic shock syndrome toxin 1 (TSST-1) superantigen is the main cause of TSS.

The current study aimed to determine the frequency of MRSA carriage and TSST-1 virulence factor among high school students.

A total of 400 nasal swab samples were randomly collected from male and female students of six different high schools in Tabriz, Iran. After confirmation of S. aureus strains by standard biochemical tests, the antibiotic sensitivity pattern of the isolates was determined by the disk diffusion method. The presence of mecA and TSST-1 genes was examined by PCR.

From 400 students, 15% (n = 60) were positive for S. aureus. Antimicrobial susceptibility testing was performed using 12 antibiotic disks. Based on the results, 100% of the isolates were resistant to ampicillin while all of them were sensitive to vancomycin. Moreover, 18.34% of the S. aureus isolates were resistant to cefoxitin and 11.67% were resistant to oxacillin. The presence of the mecA gene was confirmed in 54.54% of the cases. These results indicated oxacillin-susceptible mecA-positive S. aureus (OS-MRSA) colonization among students. Based on the PCR results, only one of the MRSA isolates belonging to a female student was positive for the TSST-1 gene.

Our findings highlight the spread of OS-MRSA among the healthy population in Tabriz, Northwest of Iran. Nevertheless, a combination of genetic and phenotypic tests is needed to accurately detect MRSA.