Molecular analysis of methicillin-resistant Staphylococcus aureus isolates from four teaching hospitals in Iran: the emergence of novel MRSA clones.

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 antimicrobial 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 multilocus sequence typing and SCCmec typing. RESULTS: Of 146 Staphylococcus aureus isolates, 24 (16.4%) isolates were identified as MRSA strains. According to antimicrobial susceptibility testing the highest resistance rates were seen for tetracycline, erythromycin, ciprofloxacin and gentamicin. All of Staphylococcus aureus isolates were susceptible to vancomycin whereas 3 (2.1%) isolates were resistant to linezolid. Three different SCCmec types were obtained among MRSA strains including 16 (66.7%) SCCmec type V, 3 (12.5%) SCCmec type III and 5 (20.8%) SCCmec 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 the fnbA, bbp and clfA genes were not detected in any MRSA isolate. MLST analysis revealed 11 sequence types among MRSA isolates as follows: ST239, ST291, ST22, ST861, ST889, 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.

Ability of biofilm production and molecular analysis of spa and ica genes among clinical isolates of methicillin-resistant Staphylococcus aureus.

OBJECTIVE: This study aimed to evaluate the phenotypic and genotypic characterization of biofilm formation and spa and ica genes among clinical isolates of methicillin-resistant Staphylococcus aureus. RESULT: This cross-sectional study was performed on 146 Staphylococcus aureus isolates from hospitalized patients in Isfahan Province Hospitals. MRSA isolates were confirmed using disk diffusion test with oxacillin disk and amplification of mecA gene by PCR assays. Ability of biofilm production was evaluated targeting the icaA and icaD genes. Of 146 Staphylococcus aureus isolates, 24 (16.4%) carried mecA genes and identified as MRSA strains. Strong ability of biofilm production was seen among 76.02% (111/146) S. aureus isolates and 87.5% (21/24) MRSA strains, respectively. Also, 75.0% (18/24) MRSA isolates carried icaA and icaD was not detected in these strains. Analysis of spa gene showed 70.83% (17/24) MRSA strains were spa positive. From which 14 and 3 strains identified with one band (150, 270, 300, 360, 400 bp) and two bands (150-300 bp), respectively. According to data obtained, the prevalence of MRSA isolates from Isfahan Province Hospitals is relatively high and a remarkable percentage of them show strong power in biofilm production. Also analysis of spa gene showed a fairly large diversity among MRSA strains.