宠物源大肠杆菌产ESBLs流行性调查与耐药机制研究

目的 为了解耐第三代头孢菌素的宠物源大肠杆菌对公共卫生的影响,测定宠物源大肠杆菌耐药性情况、超广谱β-内酰胺酶(ESBLs)的流行性及其分子传播机制,以期对其风险评估提供科学依据。方法 2014年从广州市4个动物医院采集92份患病犬猫的肛门拭子,共分离56株大肠杆菌。通过采用琼脂二倍稀释法测定17种抗菌药物的敏感性;采用PCR方法测定ESBLs的流行性及种族系统进化关系;通过接合转移试验获得CTX-M接合子,并对接合子进行复制子分型。结果 药敏试验结果表明,除黏菌素(7.1%)、头孢西丁(16.1%)和头孢他啶(10.7%)稍敏感外,有11种抗菌药物的耐药率均达到50%以上,其中动物专用的第三代头孢菌素,头孢噻肟和头孢噻呋耐药率分别为55.4%和57.1%。ESBLs检测结果表明,13株携带有CTX-M,检出率为23.2% (13/56),其中主要流行的亚型依次为CTX-M-14、CTX-M-65和CTX-M-55;7株CTX-M基因阳性菌成功接合转移,主要为FIB型复制子。未检测到TEM、OXA和SHV型。种族系统进化关系显示,分离株主要分布在A组和B1组。结论 患病犬猫的肛门拭子分离的大肠杆菌耐药性较为严重,其中以共生型为主。分离株对第三代头孢耐药的机制以产CTX-M-14,CTX-M-65和 CTX-M-55酶为主。提示宠物与人之间耐头孢菌素药物的大肠杆菌的互相传递存在风险。

Prevalence and drug-resistance mechanism of ESBLs in Escherichia coli isolates of pet origins

In order to understand the risk of the third-generation cephalosporin widely used in pets on public health, we studied the prevalence of antimicrobial resistance, distributive characteristics of extended-spectrum-β-lactamaeses (ESBLs) and molecular propagation mechanisms of the Escherichia coli isolated from pets, for providing the guidance for risk estimation. A total of 56 strains of Escherichia coli were isolated from 92 anal swabs of sick dogs and cats collected from 4 animal hospitals in Guangzhou in 2014. The susceptibility of the isolates to 17 antimicrobials was determined by ager dilution method. Phylogenetic group analysis was analyzed by PCR. The trans-conjugants were obtained by conjugative transfer test, and the replicon types for trans-conjugants were determined. Except colistin (7.1%), cefoxitin (16.1%) and ceftazidime (10.7%), resistance rates of the 11 antimicrobial agents were more than 50%, and the cefotaxime-resistance and ceftiofur-resistance rates were 55.4% and 57.1%. The results of ESBLs showed that 13 strains carried CTX-M, with the detection rate of 23.2% (13/56), and the popular subtypes were CTX-M-14, CTX-M-65 and CTX-M-55.7 CTX-M-positive trans-conjugants were obtained with main replicon type of FIB. The TEM, OXA and SHV were not detected. The isolates were mainly belonged to phylogenetic group A and group B1. In conclusion, the strains isolated from sick pets anal swab were shown in severe resistance situation, which majorly belonged to symbiotic Escherichia coli. The main mechanisms of resistance to third generation cephalosporins were CTX-M-14, CTX-M-65 and CTX-M-55. These results suggest that there is a risk of cephalosporin-resistant E. coli transmission between pets and humans.