健康鸡猪体内大肠杆菌对四环素的耐药性及耐药基因分布

【目的】四环素作为人类和动物临床上广泛使用的广谱抗生素,其耐药性问题一直为全球所关注。健康动物体内的共生性大肠杆菌作为耐药指示菌和耐药基因的贮存库,了解其对四环素的耐药性及耐药机制对于疾病的防控具有重要意义。【方法】从健康鸡、猪体内分离大肠杆菌,用微量肉汤法检测其对四环素的耐药性,并用PCR方法对耐药菌株中8种四环素耐药基因的携带情况进行调查,运用统计学方法分析鸡、猪体内大肠杆菌分离株的耐药性和耐药基因分布情况的差异。【结果】总共分离鉴定出大肠杆菌269株,其中86.2%的菌株对四环素产生了耐药性,健康猪体内大肠杆菌分离株的耐药性明显高于健康鸡体内分离株(P0.05)。tet(A)、tet(B)和tet(M)3种四环素耐药基因广泛存在于健康鸡、猪体内的共生大肠杆菌中,所携带比例分别为87.9%、28.4%和15.5%;所有对四环素耐药的大肠杆菌均携带tet(A)或tet(B)基因,其中25.0%和2.6%的耐药菌株分别携带有2种和3种耐药基因,tet(M)基因与tet(A)或tet(A)+tet(B)基因共存于对四环素耐药的大肠杆菌中;健康鸡、猪体内耐药性大肠杆菌在tet(A)+tet(M)基因携带率方面的差异具有统计学意义(P0.01)。【结论】健康鸡、猪体内的大肠杆菌分离株普遍对四环素耐药,四环素耐药基因广泛分布于大肠杆菌分离株中,大肠杆菌对四环素的耐药机制以主动外排作用为主,核糖体保护基因在大肠杆菌对四环素耐药机制方面的作用尚待进一步的研究。

Resistance to Tetracycline and Distribution of Tetracycline Resistance Determinants in Commensal Escherichia coli lsolated from Clinically Healthy Chickens and Pigs

【Objective】 Tetracycline is a broad-spectrum antibiotic used wildly in humans and animals, the resistance to tetracycline has been one of the major global concerns. Since commensal E. coli from clinically healthy animals is considered as an indicator organism of antimicrobial susceptibility and a major reservoir for tetracycline resistance genes, it is important to investigate the antimicrobial susceptibility of these isolates to tetracycline and their resistance mechanisms involved in order to prevent and treat bacterial diseases in humans and animals. 【Method】 Commensal E. coli strains were isolated from clinically healthy chickens and pigs and antimicrobial susceptibility to tetracycline was performed using the broth microdilution method, and PCR was used to detect the presence of 8 tetracycline resistance genes in tetracycline-resistant strains. Statistical analysis was performed in order to contrast the differences in both resistance to tetracycline and distribution of tetracycline resistance genes between the isolates from chickens and pigs. 【Result】 A total of 269 E. coli isolates were obtained and 86.2% of them were resistant to tetracycline. There was a significantly higher proportion of tetracycline-resistant E. coli isolated from healthy pigs than from healthy chickens (P＜0.05). Tetracycline resistance genes tet (A), tet (B) and tet (M) were widespread in commensal E. coli from clinically healthy chickens and pigs, and the carrier rates were 87.9%, 28.4% and 15.5%, respectively. All the tetracycline-resistant strains harbored tet (A) or tet (B) genes, and 25.0% and 2.6% of the isolates had two and three tetracycline resistance genes, respectively. Tet (M) was coexist with tet (A) or tet (A) + tet (B) genes. There was a statistically significant difference between the carrier rates of tet (A) + tet (M) of isolates from healthy chickens and pigs (P＜0.01). 【Conclusion】 The resistance to tetracycline was common in commensal E. coli isolated from clinically healthy chickens and pigs, and tetracycline resistance genes were widespread. The efflux of the drugs was the major resistance mechanism of commensal E. coli to tetracycline, whereas further studies should be performed to assess the influence of ribosomal protection genes on tetracycline resistance mechanism in E. coli.