Background: The global spread of methicillin-resistant Staphylococcus aureus (MRSA) infections necessitates the use of validated methods for the identification and typing of this bacterium. This study aimed to determine the distribution of main molecular types of MRSA strain circulating among hospitalized patients in teaching hospitals in Isfahan and Kashan.
Methods: A total of 146 Staphylococcus aureus strains were isolated from patients in four teaching hospitals in Isfahan and Kashan during June 2017 to September 2018. The antibiotic resistance patterns of Staphylococcus aureus strains were performed by disc diffusion method. The MRSA strains were identified phenotypically and confirmed by PCR assay. The prevalence of microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) genes among MRSA strains was evaluated by multiplex PCR. The genotypes of MRSA strains were determined by multi-locus sequence type and SCC mec typing.
Results: Of 146 Staphylococcus aureus isolates 24 (16.4%) isolates identified as MRSA strains. According to antibiotic susceptibility testing the highest resistance rates were seen to erythromycin, cefoxitin and clindamycin. All of Staphylococcus aureus isolates were sensitive to vancomycin whereas 3 (2.1%) isolates were resistant to linezolid. Three different SCC mec types were obtained among MRSA strains including 16 (66.7%) SCC mec type V, 3 (12.5%) SCC mec type III and 5 (20.8%) SCC mec type II. Of 24 MRSA isolates 20 (83.3%) carried MSCRAMMs genes including eno (70.8%), fib (54.1%) , cna (25.0%), fnbB (16.6%) , ebps 5 (20.8%), and fnbA , bbp and clfA genes were not detected. MLST analysis revealed 11 sequence types among MRSA isolates as follows: ST239, ST239, ST291, ST22, ST861, ST 889, ST8, ST59, ST343, ST772, ST6 and ST1465. Also seven MLST-based clonal complexes (CCs) were identified among MRSA strains including: CC8, CC7, CC398, CC59, CC22, CC1 and CC5.
Conclusions: A relatively high diversity was found in MRSA genotypes in Kashan and Isfahan hospitals, and seven clonal complexes were identified. Pandemic MRSA clones including CC8 and CC22 were the most prevalent clones and the novel ST types including ST1465, ST861, ST 889 and ST772 are reported for the first time in Iran in the present study. In addition the high prevalence of MSCRAMMs genes in MRSA isolates demonstrates the high potential of these strains for pathogenicity.