Dibah Solmaz, Arzanlou Mohsen, Jannati Elham, Shapouri Reza
Department of Microbiology, Zanjan Branch, Islamic Azad University, Zanjan, Iran.
Department of Microbiology, School of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran.
Iran J Microbiol. 2014 Jun;6(3):163-8.
Reports on MRSA strains are increasing worldwide. The aim of this study was to find the prevalence of MRSA strains isolated from clinical specimens and to evaluate their resistance profile. Additionally we compared the phenotypic and genotypic methods for detection of methicillin resistance.
In this cross-sectional study, a total of 41 isolates of S. aureus were collected from clinical specimens at two teaching hospitals in Ardabil, Iran. All isolates were identified at the species level by standard biochemical tests. The methicillin resistance were evaluated using three methods: PCR for mecA gene, agar dilution for determination of oxacillin MIC and disk diffusion test to detect methicillin, oxacillin and cefoxitin resistance. Antimicrobial resistance patterns were determined by disk diffusion method.
The results identified 19 (46.3%) out of 41 isolates as MRSA. Most of the MRSA strains (68.4%) were isolated from patients hospitalized in ICU. All isolates were susceptible to vancomycin, mupirocin and linezolid. Among other antibiotics co-trimoxazole was more active against MRSA isolates. Using PCR as reference method all the phenotypic tests showed 100% specificity. The sensitivity for MIC test and cefoxitin was 100% and for methicillin and oxacillin disks was 77.7% and 89.5%, respectively.
The prevalence of MRSA strains in our hospitals especially in ICU ward was high and disk diffusion testing using cefoxitin or oxacillin MIC test as an alternative to PCR for detection of MRSA is recommended.
全球范围内耐甲氧西林金黄色葡萄球菌（MRSA）菌株的报告数量不断增加。本研究旨在查明从临床标本中分离出的MRSA菌株的流行情况，并评估其耐药谱。此外，我们比较了检测甲氧西林耐药性的表型和基因型方法。
在这项横断面研究中，从伊朗阿尔达比勒市的两家教学医院的临床标本中总共收集了41株金黄色葡萄球菌分离株。所有分离株均通过标准生化试验在种水平上进行鉴定。使用三种方法评估甲氧西林耐药性：检测mecA基因的聚合酶链反应（PCR）、测定苯唑西林最低抑菌浓度（MIC）的琼脂稀释法以及检测甲氧西林、苯唑西林和头孢西丁耐药性的纸片扩散试验。通过纸片扩散法确定抗菌药物耐药模式。
结果确定41株分离株中有19株（46.3%）为MRSA。大多数MRSA菌株（68.4%）是从入住重症监护病房（ICU）的患者中分离出来的。所有分离株对万古霉素、莫匹罗星和利奈唑胺敏感。在其他抗生素中，复方新诺明对MRSA分离株的活性更强。以PCR作为参考方法，所有表型试验的特异性均为100%。MIC试验和头孢西丁的敏感性为100%，甲氧西林和苯唑西林纸片的敏感性分别为77.7%和89.5%。
我们医院中MRSA菌株的流行率很高，尤其是在ICU病房，建议使用头孢西丁纸片扩散试验或苯唑西林MIC试验作为PCR检测MRSA的替代方法。
