Luo Rong, Zhao Linna, Du Pengcheng, Luo Haipeng, Ren Xiu, Lu Pang, Cui Shenghui, Luo Yanping
Department of Food Science, National Institutes for Food and Drug Control, Beijing, China.
Nutrition and Health Research Institute, COFCO Corporation, Beijing, China.
Microb Drug Resist. 2020 Feb;26(2):89-93. doi: 10.1089/mdr.2018.0211. Epub 2019 Aug 19.
Methicillin-resistant (MRSA) isolates that carry but are oxacillin susceptible (OS-MRSA; oxacillin minimum inhibitory concentration [MIC] ≤2 μg/mL) are increasingly reported worldwide in the past decade. In this study, an OS-MRSA isolate FC1102921 from an imported meat sample was characterized and the oxacillin resistance mutation frequency and mutant prevention concentration (MPC) to oxacillin was determined. Isolate FC1102921 was negative and contained V (5C2&5), the sequence type and type were identified as ST398-t034. The MPCs of isolate FC1102921 to oxacillin was 16 μg/mL. The resistance mutation frequency of isolate FC1102921 to oxacillin was 0.036%. The expression of in isolate FC1102921 was detectable, but the expression in the mutant isolate FC1102921m increased 13.8-folds. Our data indicated that FC1102921 was not a hypermutator, and the high-resistance mutation frequency of FC1102921 was specific to oxacillin and penicillin. V region of isolate FC1102921 and FC1102921m was identical, functional and were identified in region of both isolates, and no plasmid loss was identified in mutant isolate FC1102921m. To the best of our knowledge, this is the first report of the resistance mutation frequency and MPC study of an OS-MRSA ST398-t034 isolate. The high oxacillin MPC value and high oxacillin resistance mutation frequency was not related to a curable plasmid as previously reported, which further highlighted that an in-depth study should be carried out to clarify the mechanism and role of the OS-MRSA isolates in the emergence and transmission of MRSA ST398-t034.
在过去十年中，全球范围内越来越多地报道了携带但对苯唑西林敏感（OS-MRSA；苯唑西林最低抑菌浓度[MIC]≤2μg/mL）的耐甲氧西林金黄色葡萄球菌（MRSA）分离株。在本研究中，对一株来自进口肉类样本的OS-MRSA分离株FC1102921进行了特征分析，并测定了其对苯唑西林的耐药突变频率和突变预防浓度（MPC）。分离株FC1102921为阴性，含有V（5C2&5），序列类型和型别被鉴定为ST398-t034。分离株FC1102921对苯唑西林的MPC为16μg/mL。分离株FC1102921对苯唑西林的耐药突变频率为0.036%。在分离株FC1102921中可检测到的表达，但在突变株FC1102921m中的表达增加了13.8倍。我们的数据表明，FC1102921不是一个高突变株，并且FC1102921的高耐药突变频率是苯唑西林和青霉素特有的。分离株FC1102921和FC1102921m的V区域相同，在两个分离株的区域中鉴定出功能性和，并且在突变株FC1102921m中未鉴定出质粒丢失。据我们所知，这是关于OS-MRSA ST398-t034分离株的耐药突变频率和MPC研究的首次报道。高苯唑西林MPC值和高苯唑西林耐药突变频率与先前报道的可治愈质粒无关，这进一步强调应进行深入研究以阐明OS-MRSA分离株在MRSA ST398-t034出现和传播中的机制和作用。
