Agr Typing and Detection of Mupirocin Resistance in Multi-Drug Resistant Clinical Isolates of Staphylococcus aureus in Northern Iran

Background: Mupirocin is a topical antibiotic inhibiting most Gram-positive cocci. Shortly after taking mupirocin, drug resistance emerges. This study aimed to determine mupirocin resistance in Staphylococcus aureus strains isolated from clinical specimens in Rasht. Materials & Methods: In this study, a total of ۸۵ clinical isolates of S. aureus were collected. Biofilm formation ability and antibacterial resistance patterns of isolates were investigated. Disc diffusion method and MIC determination were used to determine the susceptibility of strains to mupirocin antibiotic. Agr types, the presence of mupA, and mutation in ileS-۱ were evaluated in mupirocin non-susceptible isolates by PCR and PCR sequencing, respectively. Findings: Out of ۸۵ tested strains, ۵۷ (۶۷%) isolates were recognized as biofilm producers, and all of which showed multidrug resistance phenotype. Agr type ۱ was the most commonly detected type. Additionally, ۱۲ mupirocin-resistant strains were identified in the disc diffusion and MIC tests. A total of four strains were mup-A positive and showed high-level resistance. In sequencing and mutation evaluation of the ileS-۱ gene in eight low-level mupirocin-resistant strains, ۱۲ types of silent mutation and one type of missense mutation were determined. Conclusion: The study of mupirocin-resistant strains in this study showed the need to identify factors affecting the occurrence of resistance and to take control and prevention measures before mupirocin losses its efficacy.

Keywords:

Staphylococcus aureus , Mupirocin resistance , ileS-۱ , MupA