Yu Fangyou, Liu Yunling, Lu Chaohui, Lv Jinnan, Qi Xiuqin, Ding Yu, Li Dan, Huang Xiaoying, Hu Longhua, Wang Liangxing
Department of Laboratory Medicine, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, China.
Department of Respiratory Medicine, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, China.
BMC Microbiol. 2015 Oct 13;15:210. doi: 10.1186/s12866-015-0552-z.
A significant trend towards increased fusidic acid (FA) resistance among Staphylococcus aureus with increased duration of use is of concern. The aim of the present study is to investigate the dissemination of fusidic acid resistance among Staphylococcus aureus clinical isolates.
The susceptibility of S. aureus isolates to antimicrobial agents was determined by disc-diffusion method. The minimal inhibitory concertrations(MICs) of fusidic acid and vacomycin for fusidic acid-resisitant isolates were determined by ager dillution method. FA resistance determinants were determined by PCR and DNA sequencing. SCCmec typing, spa typing and multi-locus sequence typing were used for the determination of molecular characteristics for S. aureus isolates.
A total of 392 non-duplicate S. aureus isolates including 181 methicillin-resistant S. aureus (MRSA) isolates, which were isolated from the clinical specimens of patients at a Chinese tertiary hospital from January, 2012 to September, 2013, were collected for investigating FA resistance. Among 392 S. aureus clinical isolates tested, 56 (14.3%) with FA MIC values ranging from 2 μg/ml to ≥128 μg/ml were resistant to FA. The proportions of FA resistance among MRSA and MSSA isolates were 27.1% (49/181) and 3.3% (7/211). There was a trend of rapidly increased FA resistance among S. aureus and MRSA isolates from 5.2% and 8.9% in 2012 to 24.9% and 45.1% in 2013. Acquired FA resistance gene, fusB, was present in 73.2% (41/56) of FA-resistant S. aureus isolates. fusC and fusA mutation were not found in any of tested isolates. A total of 9 sequence types (STs) and 12 spa types were identified among the 56 FA-resistant S. aureus isolates. ST5 accounting for 66.1% (37/56) was the most prevalent ST. The majority (92.9%, 52/56) of the isolates tested belonged to clonal complex 5(CC5). t2460 was the most prevalent spa type, accounting for 67.9% (38/56) . ST5-MRSA- II-t2460 was predominant clone, accounting for 75.5% (37/49) of FA-resistant MRSA isolates and 66.1% (37/56) of FA-resistant S. aureus isolates. Five of 7 FA-resistant MSSA isolates belonged to ST630-MSSA.
Increased FA resistance among S. aureus isolates was found in China. fusB was predominant FA resistance determinant. The spread of CC5 clone, especially novel ST5-MRSA- II-t2460 clone with high-level resistance to FA, was responsible for the increase of FA resistance.
随着使用时间的延长，金黄色葡萄球菌对夫西地酸（FA）的耐药性显著增加，这一趋势令人担忧。本研究旨在调查金黄色葡萄球菌临床分离株中夫西地酸耐药性的传播情况。
采用纸片扩散法测定金黄色葡萄球菌分离株对抗菌药物的敏感性。采用琼脂稀释法测定对夫西地酸耐药的分离株中夫西地酸和万古霉素的最低抑菌浓度（MIC）。通过PCR和DNA测序确定FA耐药决定因素。采用SCCmec分型、spa分型和多位点序列分型来确定金黄色葡萄球菌分离株的分子特征。
收集了2012年1月至2013年9月在中国一家三级医院从患者临床标本中分离出的392株非重复金黄色葡萄球菌分离株，其中包括181株耐甲氧西林金黄色葡萄球菌（MRSA）分离株，用于调查FA耐药性。在测试的392株金黄色葡萄球菌临床分离株中，56株（14.3%）对FA耐药，其FA MIC值范围为2μg/ml至≥128μg/ml。MRSA和MSSA分离株中FA耐药的比例分别为27.1%（49/181）和3.3%（7/211）。金黄色葡萄球菌和MRSA分离株中FA耐药性呈快速上升趋势，从2012年的5.2%和8.9%上升至2013年的24.9%和45.1%。在73.2%（41/56）的耐FA金黄色葡萄球菌分离株中存在获得性FA耐药基因fusB。在所测试的分离株中未发现fusC和fusA突变。在56株耐FA金黄色葡萄球菌分离株中，共鉴定出9种序列类型（STs）和12种spa类型。ST5占66.1%（37/56），是最常见的ST。所测试的分离株中大多数（92.9%，52/56）属于克隆复合体5（CC5）。t2460是最常见的spa类型，占67.9%（38/56）。ST5-MRSA-II-t2460是主要克隆，占耐FA MRSA分离株的75.5%（37/49）和耐FA金黄色葡萄球菌分离株的66.1%（37/56）。7株耐FA MSSA分离株中有5株属于ST630-MSSA。
在中国发现金黄色葡萄球菌分离株中FA耐药性增加。fusB是主要的FA耐药决定因素。CC5克隆的传播，尤其是对FA具有高水平耐药性的新型ST5-MRSA-II-t2460克隆，是FA耐药性增加的原因。
