High-level aminoglycoside resistance and distribution of genesencoding aminoglycoside-modifying enzymes in methicillin-resistantStaphylococcus aureus (MRSA) isolated from northeastern Iran

Background and Aim : The resistance genes encoding aminoglycoside modification enzymes(AMEs) are now widely prevalent in different populations of Staphylococcus aureus. The studyaimed to determine the frequency of AMEs-encoding genes and their expression profile analysisin clinical isolates of MRSA.Methods : A total of ۱۰۵ S. aureus isolates were obtained from the different clinical samples; thenwere identified by current biochemical tests. The MRSA strains were identified by standardphenotypic and genotyping methods. The antibiotic resistance patterns of the isolates werecharacterized by agar disk diffusion and MIC methods. The distribution of the AMEs, mecA,femA, and femB genes was determined by multiplex PCR. The expression profile of AMEsencodinggenes was evaluated by quantitative real-time PCR.Results : The aminoglycoside resistance rates of kanamycin, tobramycin, gentamicin, amikacin,and netilmicin were ۴۷.۶%, ۴۶.۶%, ۴۵.۷%, ۴۵.۷%, and ۲۶.۶%, respectively. ۱۶.۱% and ۱.۹% ofisolates were MDR and XDR phenotypes, respectively. The aac(۶')/aph(۲'') was the most prevalent(۴۷.۸%) AME-encoding gene, followed by ant(۴')-Ia (۳۰.۴%) and aph(۳')-IIIa (۲۱.۷%). The highlevelexpression of AMEs was also detected for aac(۶')/aph(۲'').Conclusion : Our study demonstrated that the coexistence of several AMEs and the spread of theresistance determinants in MRSA clinical isolates are alarming and may contribute to thebroadening of aminoglycoside resistance spectra and limit treatment options for staphylococcalinfections.

کلیدواژه ها:

Staphylococcus aureus ، Aminoglycoside ، AMEs-encoding genes ، mecA ، Drugresistance