Investigation of Susceptibilities to benzalkonium chloride and distribution of antiseptic-resistance genes qacA/B and smr in clinical isolates of Staphylococcus aureus in Mashhad, Iran

Background and Aim : Staphylococcus aureus is one of the most important pathogens that causes hospital-acquired infections. Quaternary ammonium compounds as antiseptics were used in healthcare facilities for the prevention of nosocomial infections . methicillin-resistant S. aureus is one of the most important causes of nosocomial infections. The objective of this study is to determine antibiotic pattern of isolates , investigation of Susceptibilities to benzalkonium chloride and distribution of the qac and smr genes frequency in clinical isolates of S. aureus.Methods : Bacterial samples were collected from several parts of hospitals in Mashhad. Diagnostic tests were performed to identify S. aureus isolates. Antibiogram tests were performed by disk diffusion method by some of common antibiotics and MRSA isolates were detected by using cefoxitin disk . MIC test was done to evaluate the sensitivity of the isolates to benzalkonium chloride. Finally, the presence of qac A/B and smr genes as antiseptic resistance genes were investigated in all isolates by PCR method.Results : Among ۱۵۰ collected Staphylococcus isolates, ۱۰۰ isolates were identified as S. aureus that ۵۲ isolates were MRSA. Among all S. aureus isolates, resistance to erythromycin, clindamycin, gentamicin, tobramycin, trimethoprim sulfamethoxazole, doxycycline, penicillin, amikasin, ciprofloxacin and cefoxitin were respectively ۵۰, ۳۳, ۱۹, ۲۷, ۲۳, ۳۶, ۸۵, ۴۵, ۳۸ and ۵۲ percent. The MIC range of benzalkonium chloride for all ۱۰۰ S. aureus isolates were ۰.۰۱ – ۲ µg/mL. Molecular analysis revealed that qac A/B and smr genes were detected respectively in ۳۷ and ۴۹ percent of S. aureus isolates. Conclusion : This study showed that benzalkonium chloride is still effective for disinfection purpose. But, Penicillin resistance in Staphylococcus aureus has greatly increased over time and it is no longer as efficient as before. Also, It was found that smr genes are more common than qac A/B genes in S. aureus isolates.

Keywords:

Staphylococcus aureus , resistance genes , benzalkonium chloride