Abstract: Florfenicol is a special antibacterial agent for animals. However, with the increase of clinical dosage, the number of florfenicol-resistant strains has also been increasing year by year. Therefore, its transmission mechanism needs to be studied. This study collected samples of pig rectum and nasal cavity in the surrounding farms in Urumqi of Xinjiang, and used agar dilution method to test the susceptibility of 9 antimicrobial drugs to Staphylococcus isolated from the samples. The florfenicol-resistant test was performed by PCR to detect the resistance genes cfr, fexA and fexB, and identifie the species of Staphylococcust. The moving component IS21-558 and Tn558 transpose genes causing their transmission were detected and analyzed to explore the possible causes of the above-mentioned drug resistance genes among the bacteria. The results showed that Staphylococcus from nasal cavity and rectum had higher resistance rates to clindamycin and ofloxacin, while the resistance rate to gentamicin was lower; Staphylococcus from nasal cavity was mainly resistant to 6 (19.9%) and 7 (19.9%); while Staphylococcus from rectum was mainly resistant to 8 (27.1%); Staphylococcus from nasal cavity was more resistant than Staphylococcus from rectum. Two strains carrying cfr and fexA genes were Staphylococcus sciuri and Staphylococcus xylose, respectively. One strain carrying fexA gene was Staphylococcus saprophyticus. The fexB gene was not detected. All of the positive strains were carrying part of IS21-558 moving component and transpose Tn558, which may increase the risk of horizontal transmission of cfr and fexA genes, making it possible to produce multidrug-resistant bacteria. This study reveals that the monitoring and detection of cfr and fexA genes should be strengthened in animal husbandry and veterinary clinic, and the basic data should be provided for the further analysis of the spread and epidemic of positive resistant strains.

Key words: Staphylococcus, florfenicol-resistant gene, cfr, fexA, inserted sequence, detection

摘要： 氟苯尼考是一种特效动物专用抗菌药，随着临床用药量加大，其耐药菌株的数量也呈逐年上升的趋势，因而其传播机制亟需研究。收集新疆乌鲁木齐市周边养殖场的猪直肠和鼻腔样品，采用琼脂稀释法对样品中分离出的葡萄球菌进行临床9种常用抗菌药物的药敏试验，通过PCR方法对耐氟苯尼考的葡萄球菌进行耐药基因cfr、fexA和fexB的检测和物种鉴定，并对引起其传播的插入序列IS21-558和Tn558转座酶基因进行检测分析，探究引起上述耐药基因在菌群间可能的传播机制。结果显示鼻腔和直肠分离的葡萄球菌对克林霉素和氧氟沙星的耐药率较高，而对庆大霉素耐药率较低；鼻腔葡萄球菌主要以6耐（19.9%）和7耐（19.9%）为主；而直肠葡萄球菌主要以8耐（27.1%）为主；直肠葡萄球菌比鼻腔葡萄球菌耐药情况更加严重。筛选出两株均携带cfr和fexA基因的葡萄球菌，分别鉴定为松鼠葡萄球菌（Staphylococcus sciuri）和木糖葡萄球菌（Staphylococcus xylosus），1株携带fexA基因的葡萄球菌鉴定为腐生葡萄球菌（Staphylococcus saprophyticus），未检出携带fexB基因的菌株。通过PCR扩增发现3株阳性菌携带部分IS21-558移动元件基因和Tn558转座酶基因，可能会增加cfr和fexA基因的水平传播风险，使多药耐药细菌的产生成为可能。本研究揭示应加强畜牧兽医临床对cfr和fexA基因的检测和监测工作，为进一步分析阳性耐药菌株的传播和流行提供基础数据。

关键词: 葡萄球菌, 氟苯尼考耐药基因, cfr, fexA, 移动元件, 检测