Supplementary Material for: Molecular Characterization, Virulence Determinants, and Antimicrobial Resistance Profile of Methicillin-Resistant <b><i>Staphylococcus aureus</i></b> in the North of Iran; a High Prevalence of ST239-SCC<b><i>mec</i></b> III/t037 Clone

Objectives: Emergence and prevalence of methicillin-resistant Staphylococcus aureus (MRSA) have become a major universal health concern, limiting therapeutic options. Methods: A total number of 37 MRSA isolates, including 19 clinical isolates from hospitalized patients and 18 colonizing isolates from health care workers were identified from 3 hospitals, in Gorgan, North of Iran. Antimicrobial susceptibility test was performed using the disk diffusion method and E-test. The presence of virulence and antibiotic resistance determinants were evaluated by PCR. The genotypical characterization was further analyzed using multi-locus sequence, spa, staphylococcal cassette chromosome, mec (SCCmec), and agr typing. Results: The frequency of MRSA among S. aureus isolates was 38.14% (37/97). The most frequent S. aureus resistant isolates were found to be obstinate against penicillin (98%) and gentamicin (82.5%). Additionally, the lowest resistance rates were found against daptomycin (0%), vancomycin (2.7%), and quinupristin-dalfopristin (5.4%). All MRSA isolates were susceptible to daptomycin with minimum inhibitory concentration (MIC)50/MIC90 of 0.25/0.5 μg/mL. One isolate belonging to sequence type 239 (ST239)-SCCmecIII/t037 clone (MIC ≥16 μg/mL) was resistant to vancomycin. All but 1 isolate that shares ST22-SCCmec IV/t790 strain were positive for both tsst and pvl genes. The most predominant MRSA isolates (27%) were associated with ST239-SCCmec III/t037, and ST239-SCCmec III/t924 (16.2%) clones, subsequently. In our study, circulating MRSA strains were genetically diverse with a high prevalence of ST239-SCCmec III/t037 clone. Conclusion: These findings emphasize the need for future and continuous surveillance studies on MRSA to prevent the dissemination of existing multidrug resistance MRSA clones in an effective manner.研究目的：耐甲氧西林金黄色葡萄球菌（methicillin-resistant Staphylococcus aureus, MRSA）的出现与流行已成为全球主要的公共卫生难题，其临床治疗选择日趋受限。 方法：本研究从伊朗北部戈尔甘的3所医院中共分离得到37株MRSA菌株，其中包括19株来自住院患者的临床分离株与18株来自医护人员的定植分离株。采用纸片扩散法与E-test法开展抗菌药物敏感性试验；通过聚合酶链式反应（PCR）检测毒力与抗生素耐药决定簇的存在情况；进一步运用多位点序列分型、spa分型、葡萄球菌染色体盒mec（staphylococcal cassette chromosome mec, SCCmec）分型以及agr分型进行基因分型鉴定。 结果：金黄色葡萄球菌分离株中MRSA的检出率为38.14%（37/97）。耐药性最普遍的金黄色葡萄球菌分离株对青霉素（98%）与庆大霉素（82.5%）呈现高度耐药。此外，耐药率最低的抗菌药物为达托霉素（0%）、万古霉素（2.7%）以及奎奴普丁-达福普汀（5.4%）。所有MRSA分离株均对达托霉素敏感，其最低抑菌浓度（minimum inhibitory concentration, MIC）50/MIC90为0.25/0.5 μg/mL。1株归属序列型239（sequence type 239, ST239）-SCCmecIII/t037克隆的分离株对万古霉素耐药，其MIC≥16 μg/mL。除1株携带ST22-SCCmec IV/t790型菌株的分离株外，其余所有MRSA分离株的tsst与pvl基因均呈阳性。占比最高的MRSA分离株为ST239-SCCmec III/t037克隆（27%），其次为ST239-SCCmec III/t924克隆（16.2%）。本研究中流行的MRSA菌株遗传多样性丰富，其中ST239-SCCmec III/t037克隆的流行率较高。 结论：本研究结果凸显了未来开展持续性MRSA监测工作的必要性，以有效防控现有多重耐药MRSA克隆的传播。