Messele Yohannes E, Alkhallawi Mauida, Veltman Tania, Trott Darren J, McMeniman Joe P, Kidd Stephen P, Low Wai Y, Petrovski Kiro R
The Davies Livestock Research Centre, School of Animal and Veterinary Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
The Australian Centre for Antimicrobial Resistance Ecology, University of Adelaide, Adelaide, SA 5005, Australia.
Animals (Basel). 2022 Aug 31;12(17):2256. doi: 10.3390/ani12172256.
This study investigated the antimicrobial resistance (AMR) profile of fecal Escherichia coli isolates from beef cattle (n = 150) at entry and exit from an Australian feedlot. Sample plating on MacConkey agar and Brilliance ESBL agar differentiated generic from extended-spectrum β-lactamase (ESBL)-producing E. coli, respectively. Resistance profiles were determined by minimum inhibitory concentration (MIC) testing and further analyzed by whole-genome sequencing (WGS). At entry, the prevalence of antimicrobial resistance to amoxicillin/clavulanic acid, ampicillin, streptomycin, and trimethoprim/sulfamethoxazole was very low (0.7%, each). At the exit, the resistance prevalence was moderate to tetracycline (17.8%) and low to ampicillin (5.4%), streptomycin (4.7%), and sulfisoxazole (3.9%). The most common AMR genes observed in phenotypically resistant isolates were tet(B) (43.2%), aph(3″)-Ib and aph(6)-Id (32.4%), blaTEM-1B, and sul2 (24.3%, each), which are responsible for resistance to tetracyclines, aminoglycosides, β-lactams, and sulfonamides, respectively. The ESBL-producing E. coli were recovered from one sample (0.7%) obtained at entry and six samples (4.0%) at the exit. The ESBL-producing E. coli harbored blaTEM (29.7%), blaCTX m(13.5%), and blaCMY (5.4%). The resistance phenotypes were highly correlated with resistance genotypes (r ≥ 0.85: p < 0.05). This study demonstrated that E. coli isolated from feedlot beef cattle can harbour AMR genes, but the low incidence of medically important resistance reflected the prudent antimicrobial use in the Australian industry.
本研究调查了澳大利亚一个饲养场中肉牛（n = 150）入栏和出栏时粪便中分离出的大肠杆菌的抗菌药物耐药性（AMR）情况。分别在麦康凯琼脂和灿烂ESBL琼脂上进行样本接种，以区分普通大肠杆菌和产超广谱β-内酰胺酶（ESBL）的大肠杆菌。通过最低抑菌浓度（MIC）测试确定耐药情况，并通过全基因组测序（WGS）进一步分析。入栏时，对阿莫西林/克拉维酸、氨苄西林、链霉素和甲氧苄啶/磺胺甲恶唑的耐药率非常低（均为0.7%）。出栏时，对四环素的耐药率为中度（17.8%），对氨苄西林（5.4%）、链霉素（4.7%）和磺胺异恶唑（3.9%）的耐药率较低。在表型耐药菌株中观察到的最常见AMR基因是tet(B)（43.2%）、aph(3″)-Ib和aph(6)-Id（32.4%）、blaTEM-1B和sul2（均为24.3%），它们分别导致对四环素、氨基糖苷类、β-内酰胺类和磺胺类药物的耐药。在入栏时采集的一个样本（0.7%）和出栏时采集的六个样本（4.0%）中分离出产ESBL的大肠杆菌。产ESBL的大肠杆菌携带blaTEM（29.7%）、blaCTX m（13.5%）和blaCMY（5.4%）。耐药表型与耐药基因型高度相关（r≥0.85：p<0.05）。本研究表明，从饲养场肉牛中分离出的大肠杆菌可携带AMR基因，但具有医学重要性的耐药发生率较低，这反映了澳大利亚养殖业中抗菌药物的谨慎使用。
