Potential of ESBL-producing Escherichia coli selection in the bovine gut and in slurry after intramammary administered cephapirin and cefalonium. Potential of ESBL-producing Escherichia coli selection in the bovine gut and in slurry after intramammary administered cephapirin and cefalonium

Selection and spread of Extended Spectrum Beta-lactamase (ESBL)-producing Enterobacteriaceae within animal production systems and potential spill over to humans is a major concern. Intramammary treatment of dairy cows with first generation cephalosporins is a common practice and potentially selects for ESBL-producing Enterobacteriaceae, although it is unknown whether this really occurs in a bovine fecal environment. We aimed to study the potential effects of intramammary applied cephapirin (CP) and cefalonium (CL) to select for ESBL-producing Escherichia coli in the intestinal content of treated dairy cows and in manure slurry, using in vitro competition experiments with ESBL and non-ESBL E. coli isolates. No selection of ESBL-producing E. coli was observed at or below concentrations of 0.8 µg/ml and 4.0 µg/ml in bovine feces for CP and CL, respectively, and at or below 8.0 µg/ml and 4.0 µg/ml, respectively, in manure slurry. We calculated that the maximum concentration of CP and CL after intramammary treatment with commercial products will not exceed 0.29 µg/ml in feces and 0.03 µg/ml in manure slurry. Therefore, results of this study did not find evidence supporting selection for ESBL-producing E. coli in bovine feces or in manure slurry after intramammary use of commercial CP or CL containing products.

动物生产系统中产超广谱β-内酰胺酶（Extended Spectrum Beta-lactamase, ESBL）肠杆菌科（Enterobacteriaceae）的筛选与传播，及其向人类的潜在跨宿主传播风险，是当前备受关注的重大公共卫生议题。临床中常采用第一代头孢菌素对泌乳奶牛实施乳房内给药，该操作可能会选择性富集产ESBL肠杆菌科菌株，但目前尚不明确这一效应是否会在牛粪便环境中发生。本研究通过开展产ESBL与非产ESBL大肠杆菌（Escherichia coli, E. coli）分离株的体外竞争试验，旨在探究乳房内给药的头孢匹林（cephapirin, CP）与头孢洛宁（cefalonium, CL），能否在受试泌乳奶牛的肠道内容物及粪浆中筛选出产ESBL大肠杆菌。研究结果表明，在牛粪便体系中，当头孢匹林浓度≤0.8 μg/ml、头孢洛宁浓度≤4.0 μg/ml时，未观察到产ESBL大肠杆菌的选择性富集；在粪浆体系中，当头孢匹林浓度≤8.0 μg/ml、头孢洛宁浓度≤4.0 μg/ml时，同样未检测到该筛选效应。经测算，使用市售制剂开展乳房内给药后，奶牛粪便中头孢匹林与头孢洛宁的最大浓度均不超过0.29 μg/ml，粪浆中二者的最大浓度则均不超过0.03 μg/ml。综上，本研究未发现相关证据支持，使用市售含头孢匹林或头孢洛宁的乳房内给药产品后，会在牛粪便或粪浆中筛选出产ESBL大肠杆菌。