Uçar Şerife, Duman Yücel, Tanrıverdi Elif Seren, Tekerekoğlu Mehmet Sait, Otlu Barış
İnönü University Faculty of Medicine, Department of Medical Microbiology, Malatya, Türkiye.
Mikrobiyol Bul. 2022 Oct;56(4):593-605. doi: 10.5578/mb.20229601.
Staphylococcus aureus is an important human pathogen that causes community and hospital-acquired infections. The role of vancomycin in the treatment of methicillin-resistant S.aureus infections is indisputable. However, vancomycin intermediate susceptible S.aureus (VISA) and heterogeneously VISA (hVISA) isolates, that cause treatment failures during the use of vancomycin, cannot be detected by routine laboratory methods. The gold standard method for the detection of these isolates is the population profile analysis-area under the curve (PAP-AUC) method. In this study, it was aimed to determine the presence of mecA and mecC gene regions that cause methicillin resistance, the clonal relationship between isolates, and the presence of VISA and hVISA. A total 68 methicillin-resistant S.aureus (MRSA) strains were included in this study which were isolated in the microbiology laboratory of the hospital between 2015- 2020. Identification of the isolates were determined by matrix assisted laser desorption ionization-time of flight mass spectrophotometry (VITEK MS, BioMérieux, France). Methicillin resistance was investigated by disk diffusion method using cefoxitin (30 µg, Bioanalyse, Türkiye) disk and vancomycin MIC values were determined by broth microdilution method. mecA and mecC gene regions were investigated by polymerase chain reaction (PCR) method. The presence of VISA and hVISA were investigated by modified agar screening, macro gradient diffusion test and confirmated by PAP-AUC methods, and the clonal relationship between isolates were investigated by pulsed field gel electrophoresis method. The mecA gene region was determined in all isolates, but the mecC gene region was not found in any of the isolates. The MIC50 value of the isolates was determined as 1 μg/mL and the MIC90 value was determined as 2 μg/mL by broth microdilution method. Six VISA and four hVISA suspected strains were detected by a modified agar screening method. Among the isolates identified as suspicious by the modified agar screening method, one isolate was evaluated as VISA and one isolate was evaluated as hVISA by the gold standard PAP-AUC method. No dominant epidemic isolate has been identified by PFGE. As a result, VISA and hVISA were determined in the hospital. The increase in these isolates is a serious concern. For this reason, it is believed that it would be beneficial to investigate the VISA/hVISA ratios in MRSA isolates at certain periods, and to take necessary infection control measures to implement measures and practices to prevent the spread of these isolates in the community and hospital environment.
金黄色葡萄球菌是一种重要的人类病原体，可引起社区获得性感染和医院获得性感染。万古霉素在治疗耐甲氧西林金黄色葡萄球菌感染中的作用是无可争议的。然而，常规实验室方法无法检测到导致万古霉素治疗失败的万古霉素中介敏感金黄色葡萄球菌（VISA）和异质性VISA（hVISA）分离株。检测这些分离株的金标准方法是群体谱分析-曲线下面积（PAP-AUC）法。在本研究中，旨在确定导致甲氧西林耐药的mecA和mecC基因区域的存在、分离株之间的克隆关系以及VISA和hVISA的存在情况。本研究共纳入了68株耐甲氧西林金黄色葡萄球菌（MRSA）菌株，这些菌株于2015年至2020年期间在医院微生物实验室分离得到。通过基质辅助激光解吸电离飞行时间质谱法（VITEK MS，法国生物梅里埃公司）对分离株进行鉴定。采用头孢西丁（30μg，土耳其Bioanalyse公司）纸片扩散法研究甲氧西林耐药性，采用肉汤微量稀释法测定万古霉素MIC值。通过聚合酶链反应（PCR）法研究mecA和mecC基因区域。通过改良琼脂筛选、宏观梯度扩散试验研究VISA和hVISA的存在情况，并通过PAP-AUC法进行确认，通过脉冲场凝胶电泳法研究分离株之间的克隆关系。所有分离株均检测到mecA基因区域，但未在任何分离株中发现mecC基因区域。通过肉汤微量稀释法测定分离株的MIC50值为1μg/mL，MIC90值为2μg/mL。通过改良琼脂筛选法检测到6株疑似VISA和4株疑似hVISA菌株。在改良琼脂筛选法鉴定为可疑的分离株中，通过金标准PAP-AUC法，一株分离株被评估为VISA，一株分离株被评估为hVISA。PFGE未鉴定出优势流行株。结果，在医院中检测到了VISA和hVISA。这些分离株的增加令人严重担忧。因此，认为在特定时期调查MRSA分离株中的VISA/hVISA比例，并采取必要的感染控制措施以实施预防这些分离株在社区和医院环境中传播的措施和做法将是有益的。
