Comparison of Antibiotic Susceptibility Pattern and Prevalence of mecA and agr Genes among Staphylococcus aureus Isolated from Blood and Urinary Infections in Sanandaj, West of Iran.

Background and Objectives:Staphylococcus aureus is one of the main causes of drug resistant infections in the community and the hospital. The resistance of this microorganism to methicillin is due to the presence of mecA gene, which is located on a chromosomal cassette called SCCmec types . Recently, the effect of integrons (int) on the transfer of antibiotic resistance among S. aureus has been well recognized . This bacterium has an accessory gene regulatory (agr) system that plays a role in controlling the expression of virulence genes . In this study, we compared the antibiotic susceptibility pattern and prevalence of mecA, agr genes and integron classes 1-3 among S. aureus isolated from blood with urine samples of patients admitted to Besat and Tohid Hospitals of Sanandaj city, west of Iran. Materials and Methods: Between October and December 2017, 40 S. aureus were isolated from urinary tract infection (UTI) and 16 from blood infection. The antibiotic susceptibility test for 11 antibiotics was performed by agar disk diffusion method and for vancomycin by E-test according to the CLSI 2017 (Clinical and Laboratory Standards Institute). After extraction of DNA from the isolates by boiling method, the prevalence rates of mecA, agrI-IV types and int I,II, III were investigated using polymerase chain reaction. Results: Of the 40 strains isolated from UTI, the sensitivity to mupirocin was 97.5 %, followed by trimethoprim- sulfamethoxazole 95%, gentamicin 87.5%, cefoxitin 80%, tetracycline and clindamycin 77% (each), ciprofloxacin 72%, erythromycin 55%, and penicillin 5%. All the isolates (100%) were susceptible to vancomycin and linezolid. Among the 16 strains isolated from blood, the sensitivity to trimethoprim-sulfamethoxazole and cefoxitin was 93.7% (each), gentamicin 87.5%, tetracycline and ciprofloxacin 75% (each), erythromycin 70%, clindamycin 68.7%, and penicillin 0%. All the isolates (100%) were susceptible to vancomycin, mupirocin and linezolid. Of the 40 strains isolated from UTI, 10% harbored mecA and 12.5% harbored Int1. Integron classes 2 and 3 were not found. Furthermore, 10% of the 40 isolates carried agrI and 30% agrIII. However, agrII and IV were not found. Of the 16 strains isolated from blood infection, 6.25% harbored mecA. Integron classes 1-3 were not detected. Moreover, 31.2% of the 16 isolates carried agrI and 25% carried agrIII. agr II and IV were not found. Conclusion: According to the susceptibility test, prevalence of mecA and integrons, the results showed the high susceptibility of the isolates from blood infection group to the antibiotics in comparison to the isolates from UTI group. Although both the groups of isolates carried agr I and III, the agrI was predominant in the blood infection group and agrIII in the UTI group. We suggest that vancomycin and linezolid are suitable drugs for the treatment of both the groups of infections, but care should be taken in order to avoid the emergence of antibiotic resistance.