Smith H W, Tucker J F
J Hyg (Lond). 1975 Oct;75(2):275-92. doi: 10.1017/s0022172400047306.
Chickens in groups of 40 were infected orally with a nalidixic acid-resistant mutant of Salmonella typhimurium and then fed continuously on diets containing ampicillin, chloramphenicol, furazolidone, neomycin, oxytetracycline, polymixin, spectinomycin, streptomycin or a mixture of trimethoprim and sulphadiazine. The amount of S. typhimurium excreted in their faeces was estimated at intervals by culture on brilliant green agar containing sodium nalidixate, both direct and after enrichment in selenite broth; the amount of Escherichia coli excreted was estimated by culture on MacConkey agar. The feeding of diets containing 500 mg./kg. of ampicillin, furazolidone, neomycin, polymixin, spectinomycin or streptomycin or 100 mg./kg. of trimethoprim and 500 mg./kg. of sulphadiazine for 46 days reduced to a varying degree the amount of S. typhimurium and E. coli excreted, the greatest reduction in S. typhimurium being brought about by the last treatment. The effect was less obvious when the concentration of the antibiotics in the food was decreased fivefold. An important reason for the very limited effect of some of the antibiotics was the emergence of antibiotic-resistant populations of S. typhimurium and E. coli. High concentrations of antibiotic-resistant organisms also arose in the faeces of the chickens fed diets containing tetracyclines and chloramphenicol, treatments which had no apparent effect on the amount of S. typhimurium and E. coli excreted. Much of the antibiotic resistance encountered was determined by R factors, a particular R factor usually being found in the E. coli populations of individual chickens before it was found in their S. typhimurium populations. No S. typhimurium or E. coli were isolated that possessed R factors determining resistance to polymixin, furazolidone or trimethoprim. No S. typhimurium or E. coli were isolated that were polymixin-resistant and no S. typhimurium that were furazolidone-resistant. The few trimethoprim-resistant S. typhimurium isolated were thymine-dependent. The feeding of diets containing the higher concentrations of trimethoprim/sulphadiazine, neomycin, furazolidone or ampicillin for 9 days reduced the amount of S. typhimurium excreted. After the withdrawal of these diets, the amount of S. typhimurium excreted increased to the numbers found in chickens given ordinary diets throughout; the chickens that had been given trimethoprim/sulphadiazine or furazolidone did not remain faecal excreters of S. typhimurium longer than the chickens that had been given ordinary diets. Similar results were obtained with trimethoprim/sulphadiazine when the start of the 9-day treatment period was delayed for an extra 9 days or when it was extended to 18 days.
将40只鸡分为一组，经口感染鼠伤寒沙门氏菌的耐萘啶酸突变株，然后持续饲喂含氨苄青霉素、氯霉素、呋喃唑酮、新霉素、土霉素、多粘菌素、壮观霉素、链霉素或甲氧苄啶与磺胺嘧啶混合物的日粮。每隔一段时间，通过在含萘啶酸钠的亮绿琼脂上培养，直接培养以及在亚硒酸盐肉汤中富集后培养，来估计它们粪便中排出的鼠伤寒沙门氏菌数量；通过在麦康凯琼脂上培养来估计排出的大肠杆菌数量。饲喂含500毫克/千克氨苄青霉素、呋喃唑酮、新霉素、多粘菌素、壮观霉素或链霉素的日粮，或含100毫克/千克甲氧苄啶和500毫克/千克磺胺嘧啶的日粮46天，不同程度地减少了排出的鼠伤寒沙门氏菌和大肠杆菌数量，最后一种处理对鼠伤寒沙门氏菌的减少作用最大。当食物中抗生素浓度降低五倍时，效果不太明显。某些抗生素效果非常有限的一个重要原因是出现了耐抗生素的鼠伤寒沙门氏菌和大肠杆菌群体。在饲喂含四环素和氯霉素日粮的鸡的粪便中也出现了高浓度的耐抗生素生物，这些处理对排出的鼠伤寒沙门氏菌和大肠杆菌数量没有明显影响。所遇到的许多抗生素抗性是由R因子决定的，通常在个别鸡的大肠杆菌群体中先发现特定的R因子，然后才在它们的鼠伤寒沙门氏菌群体中发现。未分离出具有决定对多粘菌素、呋喃唑酮或甲氧苄啶抗性的R因子的鼠伤寒沙门氏菌或大肠杆菌。未分离出耐多粘菌素的鼠伤寒沙门氏菌或大肠杆菌，也未分离出耐呋喃唑酮的鼠伤寒沙门氏菌。分离出的少数耐甲氧苄啶的鼠伤寒沙门氏菌是胸腺嘧啶依赖型的。饲喂含较高浓度甲氧苄啶/磺胺嘧啶、新霉素、呋喃唑酮或氨苄青霉素的日粮9天，减少了排出的鼠伤寒沙门氏菌数量。停止饲喂这些日粮后，排出的鼠伤寒沙门氏菌数量增加到整个实验过程中饲喂普通日粮的鸡所排出的数量；饲喂甲氧苄啶/磺胺嘧啶或呋喃唑酮的鸡作为鼠伤寒沙门氏菌粪便排出者的时间并不比饲喂普通日粮的鸡长。当9天治疗期开始推迟9天或延长至18天时，用甲氧苄啶/磺胺嘧啶也得到了类似结果。
