The prevalence of antiseptic resistance genes (qacA/B and smr) and antibiotic resistance in clinical Staphylococcus aureus strains

Staphylococcus aureus is an organism of major medical importance, leading to skin and soft tissue infections, bacteremia, and endocarditis. S.aureus isolates are becoming increasingly resistant to numerous antimicrobial agents including antiseptics and disinfectants. Quaternary ammonium compounds are disinfectants that play an important role in the control of nosocomial infections. Presence of genes conferring resistance to quaternary ammonium compounds is widely distributed among clinical staphylococci isolated from certain areas of the world. In this present study, we aimed to study the prevalence of antiseptic resistance genes (qac A/B, smr) and antibiotic resistance in clinical S.aureus strains, and also to detect the possible relationship between antiseptic and antibiotic resistance. For this purpose, the presence of qac A/B and smr genes in 50 methicillin-susceptible S.aureus (MSSA) and 50 methicillin-resistant S.aureus (MRSA) clinical isolates (78 abscess, 13 blood, 3 sputum, 3 tracheal aspirate, 2 nostril swab, 1 urine) was detected by using multiplex polymerase chain reaction. The susceptibility of S.aureus strains to different antibiotics (cefoxitin, erythromycin, clindamycin, rifampin, tetracycline, ciprofloxacin, gentamicin, trimethoprim-sulfamethoxazole, vancomycin, teicoplanin) was determined by disk diffusion method according to the recommendation of Clinical Laboratory Standards Institute (CLSI). smr genes were found in 18 (36%) of 50 MRSA and qacA/B genes in 2 (4%) of 50 MSSA strains. Presence of smr gene only in MRSA strains in comparison to MSSA strains was found to be statistically significant (p< 0.001). The rates of antibiotic resistance in S.aureus strains were as follows; gentamicin 89%, tetracycline 57%, rifampin and ciprofloxacin 46%, and macrolides (erythromycin and clindamycin) 32%. No resistance was detected against trimethoprim-sulfamethoxazole, vancomycin and teicoplanin. On the other hand, presence of inducible macrolid-lincosamide-streptogramin B (iMLSB) resistance phenotype in 8 (44.5%) out of 18 smr positive strains compared to 2 (6.25%) out of 32 smr negative strains was statistically significant (p< 0.001). We concluded that smr genes were detected to be more prevalent than qacA/B genes in our clinical S.aureus isolates. smr genes were found only in MRSA strains whereas low number of qacA/B genes were found only in MSSA strains. Presence of smr genes concomitantly with iMLSB type resistance in MRSA strains was recorded