Langford F M, Weary D M, Fisher L
Department of Veterinary Clinical Studies, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, Easter Bush, Midlothian, EH25 9RG, UK.
J Dairy Sci. 2003 Dec;86(12):3963-6. doi: 10.3168/jds.S0022-0302(03)74006-5.
Dairy calves are commonly fed milk from cows treated with antibiotics. The concentration of beta-lactam antibiotic residues found in milk from treated cows was used to determine the range of concentrations of penicillin used in a dose-regulated experiment. Thirty-one Holstein calves were randomly assigned to milk with penicillin G added at concentrations of 0, 6.25, 12.5, 25, and 50 microl/kg. Fecal swabs were taken from each calf twice weekly. Resistance to penicillin was tested by measuring the zone of inhibition in bacterial growth around a disk impregnated with the antibiotic. Inhibition was greatest for bacteria from calves fed milk with no penicillin (2.89 +/- 0.14 mm), and declined as the penicillin dose provided in the milk increased (to a low of 0.70 +/- 0.10 for the 50 microl/kg treatment group). In conclusion, resistance of gut bacteria to antibiotics increases with increasing concentrations of penicillin in the milk fed to dairy calves.
乳牛犊通常喂食来自用抗生素治疗过的奶牛的牛奶。用治疗过的奶牛的牛奶中发现的β-内酰胺类抗生素残留浓度来确定剂量调节实验中使用的青霉素浓度范围。31头荷斯坦犊牛被随机分配到添加浓度为0、6.25、12.5、25和50微克/千克青霉素G的牛奶组。每周两次从每头犊牛采集粪便拭子。通过测量浸有抗生素的圆盘周围细菌生长的抑菌圈来测试对青霉素的耐药性。对于喂食不含青霉素牛奶的犊牛的细菌，抑菌作用最大（2.89±0.14毫米），并且随着牛奶中提供的青霉素剂量增加而下降（对于50微克/千克治疗组，低至0.70±0.10）。总之，随着喂食给乳牛犊的牛奶中青霉素浓度的增加，肠道细菌对抗生素的耐药性增强。
