The prevalence of exotoxins, adhesion, and biofilm-related genes in Staphylococcus aureus isolates from the main burn center of Tehran, Iran

Objectives: The present study investigated the prevalence of genes encoding for exotoxins, adhesion and biofilm factors in Staphylococcus aureus isolates obtained from samples in a referral burn hospital in Tehran, Iran.

Materials and methods: S. aureus isolates obtained from patients, personnel and surfaces in the wards of a burn hospital were identified and confirmed by biochemical and molecular tests, respectively. The susceptibility of isolates was determined using the disk diffusion method. Virulence factors were detected by multiplex PCR.

Results: The frequency of hla, hlb, hld, hlg, tst and pvl genes was 92.8%, 34.7%, 89.8%, 11.9%, 10.7%, and 0.5% respectively. The results revealed that the hla gene had the highest frequency among isolates (94.4% for methicillin-resistant S. aureus (MRSA) and 89.8% for methicillin-susceptible S. aureus (MSSA)). The most prevalent adhesion and biofilm-related gene was eno (85.6%). The prevalence of the remaining genes was as follows: fib (71.8%), clfB (70%), cna (59.2 %), fnbB (17.9%), icaA (72.4%), and icaD (85.6%). The incidence of fib, hlb, hlg, and tst genes was significantly higher in MRSA isolates compare to the MSSA isolates. Moreover, the resistance rates for all antibiotics were higher is MRSA isolates except for nitrofurantoin and chloramphenicol antibiotics.

Conclusion: Data indicate the high prevalence rates of virulence factors among S. aureus isolates, especially MRSA strains in the burn hospital. This should to be taken into account in the development of an effective infection control policy and continuous monitoring of drug resistance in hospitals.