Molecular analysis and typing of methicillin resistance Staphylococcus aureus strains isolated from hospitalized patients

The prevalence of Staphylococcus aureus, as one of the most common nosocomial pathogens, is increasing annually and is becoming a major public health concern. One of the serious threats associated with clinical isolates of MRSA is lack of data regarding the molecular characterization of these isolates. The aim of the present study was to identify resistance encoding genes and molecular characteristics of methicillin-resistant S. aureus strains isolated from hospitalized patients in 2017. During a 10-month period, 112 MRSA strains isolated from hospitalized patients were investigated. In vitro antimicrobial susceptibility of the isolates was assessed using the disk diffusion and micro-broth dilution methods. Conventional PCR was performed to detect resistance encoding genes. Different types of SCCmec were analyzed using multiplex PCR. The results of antibiotic susceptibility testing showed that 91.1% of isolates were resistant to penicillin, 65.2% to ceftriaxon, 63.4% to erythromycin, 56.3% to kanamycin, 52.7% to Clindamycin, 50% to amikacin, 45.5% to gentamicin, 26.8% to tobramycin, 18.8% to quinupristin/dalfopristin, and 11.6% were resistant to trimetoprim-sulfamethoxazole. The most prevalent resistance gene belonged to ant(4΄)- Ia (73.2%) followed by aac(6΄)-Ie/aph(2˝) (59.8%), tet(M) (57.1%), msr(A) (36.7%), aph(3΄)-IIIa (35.7%), erm(A) (33.9%), msr(B) (24.1%), erm(B) (17%), erm(C) (15.2%), and mupA (10.7%). Our findings revealed that the most common SCCmec type was III (53.6%) followed by types I (23.3%), IV (14.3%), and II (8.9%). High-level mupirocin-resistant strains belonged to SCCmec types III (5.4%), IV (4.4%), and I (0.9%), while all the low-level mupirocin resistant strains belonged to SCCmec type III (15.2%). It seems that there is a genetic diversity among MRSA circulating in studied hospitals that highlights the need to implement appropriate infection control policies in order to decrease dissemination of multi-drug resistance MRSA types in our hospitals.