a Department of Microbiology , Ahar Branch, Islamic Azad University , Ahar , Iran.
b Department of Microbiology , School of Medicine, Tabriz University of Medical Sciences , Tabriz , Iran.
Artif Cells Nanomed Biotechnol. 2016 Sep;44(6):1464-8. doi: 10.3109/21691401.2015.1041639. Epub 2015 May 7.
Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common organisms isolated from clinical samples, and has been associated with morbidity and mortality among hospitalized patients. The aim of this study was to evaluate the prevalence and antibiotic susceptibility patterns among MRSA and methicillin-sensitive S. aureus (MSSA) isolates collected from four hospitals in Iran.
A total of 183 isolates of S. aureus were collected from various clinical specimens of four hospitals in Iran. The isolates were identified by using the conventional biochemical tests. Three methods-oxacillin agar disk diffusion, oxacillin agar screening, and PCR- were applied to determine susceptibility to oxacillin. The conventional disk agar diffusion test was used to evaluate the antibiotic sensitivity of our isolates against 15 antibiotics, according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI).
Of 183 isolates, 77 isolates (42.1%) were found to be MRSA, by the PCR method. The highest antibiotic resistance was found to be against penicillin, co-trimoxazole, erythromycin, and tetracycline respectively. All isolates were susceptible to vancomycin, according to the results of disk agar diffusion. Among other antibiotics, teicoplanin (84%) and fusidic acid (80.5%) were more active against MRSA isolates. For the different methods evaluated, the sensitivities and specificities were as follows: for disk agar diffusion (84.9% and 95.9%) and for agar screening test with oxacillin concentrations of 0.6 μg/ml (70.8% and 97.4%), 4 μg/ml (96.1%and 97.2%) and 6 μg/ml (96% and 96.3%), respectively.
The results of our study showed that 47% of S. aureus isolates were MRSA. Overall, in this research study, resistance to all test antimicrobial agents in MRSA isolates were higher than that of MSSA isolates. Our results also revealed that 85% of mecA-positive isolates and 15% of mecA-negative isolates were resistant to methicillin; while 96% of mecA-negative isolates were sensitive to methicillin. Meanwhile 4% of mecA-positive isolates were also sensitive to methicillin.
耐甲氧西林金黄色葡萄球菌（MRSA）是从临床样本中分离出的最常见的病原体之一，与住院患者的发病率和死亡率有关。本研究的目的是评估从伊朗四家医院采集的耐甲氧西林金黄色葡萄球菌（MRSA）和甲氧西林敏感金黄色葡萄球菌（MSSA）分离株的流行率和抗生素药敏模式。
从伊朗四家医院的各种临床标本中采集了 183 株金黄色葡萄球菌分离株。通过常规生化试验鉴定分离株。采用苯唑西林琼脂扩散法、苯唑西林琼脂筛选法和 PCR 法三种方法检测对苯唑西林的敏感性。根据临床和实验室标准协会（CLSI）的指南，采用常规纸片琼脂扩散试验评估我们的分离株对 15 种抗生素的药敏性。
通过 PCR 法，183 株分离株中有 77 株（42.1%）被鉴定为 MRSA。对青霉素、复方新诺明、红霉素和四环素的耐药率最高。根据纸片琼脂扩散试验的结果，所有分离株均对万古霉素敏感。在其他抗生素中，替考拉宁（84%）和夫西地酸（80.5%）对 MRSA 分离株的活性更强。对于评估的不同方法，敏感性和特异性如下：纸片琼脂扩散法（84.9%和 95.9%）和苯唑西林浓度为 0.6μg/ml 的琼脂筛选试验（70.8%和 97.4%）、4μg/ml（96.1%和 97.2%）和 6μg/ml（96%和 96.3%）。
我们的研究结果表明，47%的金黄色葡萄球菌分离株为 MRSA。总的来说，在本研究中，MRSA 分离株对所有测试抗菌药物的耐药性均高于 MSSA 分离株。我们的结果还表明，85%的 mecA 阳性分离株和 15%的 mecA 阴性分离株对甲氧西林耐药；而 96%的 mecA 阴性分离株对甲氧西林敏感。同时，4%的 mecA 阳性分离株也对甲氧西林敏感。
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