Center for Comparative Epidemiology, College of Veterinary Medicine, A-109 Veterinary Medical Center, Michigan State University, East Lansing, MI 48824-1314, USA.
Foodborne Pathog Dis. 2010 Oct;7(10):1193-201. doi: 10.1089/fpd.2010.0551.
The objectives of this study were to report an outbreak of highly drug-resistant Salmonella enterica serotype Oranienburg in dairy calves, and conduct an epidemiological investigation of Oranienburg identified on a dairy herd during a study to determine whether discontinuing feeding medicated milk replacer to preweaned dairy calves resulted in increased antimicrobial susceptibility in enteric bacteria. Calf fecal samples and swabs of calf and maternity pens were collected monthly over 18 months. Samples were streaked onto XLT-4 agar and characteristic colonies were subjected to biochemical tests to confirm Salmonella. Strain relatedness was examined by Xbal and BlnI pulsed-field gel electrophoresis analysis on 62 randomly selected isolates. Antimicrobial susceptibility testing, using automated microbroth dilution, was conducted using a panel containing tetracycline, amikacin, amoxicillin-clavulanic acid, ampicillin, ceftiofur, ceftriaxone, cephalothin, chloramphenicol, ciprofloxacin, cefoxitin, gentamicin, kanamycin, nalidixic acid, streptomycin, sulfamethoxazole, and trimethoprim-sulfamethoxazole. A total of 190 Salmonella spp. were isolated from 604 calf and 36 pen samples, of which 86% were Oranienburg and 97% were resistant to at least 9 agents. Environmental isolates had lower levels of resistance than fecal isolates. Pulsed-field gel electrophoresis analysis identified three strains: the most common strain was consistently present before the outbreak and at its peak. One strain was exclusively an environmental isolate, with little antimicrobial resistance. Multiresistant isolates with resistance to ciprofloxacin appeared early in the outbreak, and were replaced by multiresistant isolates with resistance to cephalothin. The differences in strains and resistance patterns suggest that the strains of Oranienburg found in fecal isolates may have different origins from environmental isolates.
本研究的目的是报告一起在奶牛犊牛中发生的高度耐药沙门氏菌肠炎亚种奥兰宁堡疫情，并对在一项研究中发现的奶牛群中的奥兰宁堡进行流行病学调查，以确定停止给未断奶的奶牛犊牛喂食含药代乳品是否会导致肠道细菌对抗菌药物的敏感性增加。在 18 个月的时间里，每月收集一次犊牛粪便样本和犊牛及产房栏的拭子。将样本划线接种于 XLT-4 琼脂上，对特征性菌落进行生化试验以确认是否为沙门氏菌。对 62 株随机选择的分离株进行 Xbal 和 BlnI 脉冲场凝胶电泳分析，以检测菌株间的亲缘关系。使用包含四环素、阿米卡星、阿莫西林-克拉维酸、氨苄西林、头孢噻呋、头孢曲松、头孢噻吩、氯霉素、环丙沙星、头孢西丁、庆大霉素、卡那霉素、萘啶酸、链霉素、磺胺甲恶唑和甲氧苄啶的药敏试验板进行药敏试验，采用自动化微量肉汤稀释法进行。从 604 份犊牛和 36 份栏样本中分离出 190 株沙门氏菌，其中 86%为奥兰宁堡，97%至少对 9 种药物耐药。环境分离株的耐药水平低于粪便分离株。脉冲场凝胶电泳分析鉴定出 3 种菌株：最常见的菌株在疫情爆发前和高峰期一直存在。一种菌株是环境分离株，抗菌药物耐药性较低。在疫情早期出现了对环丙沙星耐药的多耐药株，随后被对头孢噻吩耐药的多耐药株所取代。菌株和耐药模式的差异表明，粪便分离株中的奥兰宁堡菌株可能与环境分离株的来源不同。
