Guangdong Key Laboratory for Veterinary Drug Development and Safety Evaluation, South China Agricultural University, 510642 Guangzhou, China.
National Risk Assessment Laboratory For Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, 510642 Guangzhou, China.
Poult Sci. 2021 Feb;100(2):1093-1097. doi: 10.1016/j.psj.2020.11.049. Epub 2020 Nov 30.
Florfenicol, apramycin, and danofloxacin are antibiotics approved only for veterinary use and that have good therapeutic effects on chicken respiratory infections caused by Escherichia coli. We established epidemiological cutoff values (ECV) for these antibiotics using 363 E. coli isolates from tracheal samples of chickens in 5 veterinary clinics in Guangdong Province, China. The minimum inhibitory concentrations (MIC) were determined using the agar dilution method as per Clinical and Laboratory Standards Institution guidelines. The ECV were then calculated using the statistical method and verified by normalized resistance interpretation and ECOFFinder software programs. The ECV of florfenicol, apramycin, and danofloxacin against E. coli were 16, 16, and 0.125 μg/mL, respectively. Susceptibility tests indicated that these isolates were resistant to florfenicol (66.7%), apramycin (22.3%), and danofloxacin (92.3%). Strains carrying floR were distributed in the range of MIC ≥32 μg/mL for florfenicol. Apramycin resistance was found in 77 strains (77/363, 21.1%), and isolates that carried aac(3)-IV were all in the range of MIC ≥512 μg/mL. Danofloxacin resistance was found in the range of MIC ≤0.125 μg/mL, but there were no mutations in the quinolone resistance-determining regions and plasmid-mediated quinolone resistance genes qnrA, qnrB, qnrC, qnrD, aac-(6')-Ib-cr, qep, and oqxB. The presence of the qnrS gene was verified in a few of the strains with an MIC of 0.06 μg/mL. The establishment of ECV was significant for monitoring of resistance development and therapy guidance.
氟苯尼考、安普霉素和丹诺沙星仅获准用于兽医，对由大肠杆菌引起的鸡呼吸道感染具有良好的治疗效果。我们使用来自广东省 5 家兽医诊所鸡气管样本中的 363 株大肠杆菌分离株建立了这些抗生素的流行病学截断值（ECV）。根据临床和实验室标准协会指南，使用琼脂稀释法测定最小抑菌浓度（MIC）。然后使用统计方法计算 ECV，并通过标准化耐药解释和 ECOFFinder 软件程序进行验证。氟苯尼考、安普霉素和丹诺沙星对大肠杆菌的 ECV 分别为 16、16 和 0.125μg/ml。药敏试验表明，这些分离株对氟苯尼考（66.7%）、安普霉素（22.3%）和丹诺沙星（92.3%）耐药。携带 floR 的菌株分布在氟苯尼考 MIC≥32μg/ml 的范围内。发现 77 株（77/363，21.1%）对安普霉素耐药，携带 aac(3)-IV 的分离株均在 MIC≥512μg/ml 的范围内。丹诺沙星耐药发生在 MIC≤0.125μg/ml 范围内，但喹诺酮耐药决定区和质粒介导的喹诺酮耐药基因 qnrA、qnrB、qnrC、qnrD、aac-(6')-Ib-cr、qep 和 oqxB 没有突变。在 MIC 为 0.06μg/ml 的少数菌株中证实了 qnrS 基因的存在。ECV 的建立对于监测耐药性发展和治疗指导具有重要意义。
