Muñoz-Vargas Lohendy, Finney Sarah K, Hutchinson Holden, Masterson Margaret A, Habing Greg
1 Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University , Columbus, Ohio.
2 Department of Animal Sciences, College of Food, Agricultural, and Environmental Sciences, The Ohio State University , Columbus, Ohio.
Foodborne Pathog Dis. 2017 Nov;14(11):678-685. doi: 10.1089/fpd.2017.2303. Epub 2017 Sep 14.
The objective of this study was to determine the prevalence, serotypes, antimicrobial resistance phenotypes, and pulsed-field gel electrophoresis (PFGE) patterns of Salmonella recovered in feces and mesenteric and prefemoral lymph nodes (LNs) from cohorts of calves with and without a confirmed outbreak of salmonellosis. In a prospective cohort study, 160 calves from four farms without a reported outbreak (nonoutbreak farms) were sampled at farm and harvest. In addition, harvest samples from 80 calves of two farms with a confirmed outbreak (outbreak farms) were collected. A culture protocol for Salmonella isolation was applied for all samples and recovered isolates were further characterized by serotyping, antimicrobial susceptibility testing, and PFGE. Among nonoutbreak farms, Salmonella was recovered from 0% (0/160) farm fecal samples, 3.7% (6/160) harvest fecal swabs, 21.9% (35/160) mesenteric LNs, and 0.6% (1/160) prefemoral LNs. Serotypes identified in nonoutbreak herds included Salmonella Typhimurium, Cerro, Hartford, and Newport. Most isolates (64.3%, 27/42) exhibited a unique multidrug-resistant (MDR) phenotype, including resistance to extended-spectrum cephalosporins. Salmonella prevalence in harvest fecal samples and prefemoral LNs among calves from outbreak farms was numerically higher, but not significantly different than those without an outbreak. Serotypes recovered from outbreak farms included Salmonella Heidelberg and Typhimurium, and the monophasic Salmonella Typhimurium strains 4,5,12:i:- and 4,12:i:-, which have been also reported as highly pathogenic in humans. All isolates (33/33) exhibited an MDR phenotype. Salmonella strains recovered from ill calves in two outbreaks had indistinguishable PFGE patterns, suggesting between-farm transmission. In addition, the genotype of Salmonella Heidelberg causing an outbreak among calves was recovered from three prefemoral LNs of surviving members of the cohort at harvest. Implementation of preharvest biosecurity measures (limited personnel and visitor traffic, vehicle, footwear, and utensils disinfection) should be highly recommended to decrease the prevalence of Salmonella on farms and safeguard the food safety.
本研究的目的是确定在有或没有确诊沙门氏菌病暴发的犊牛群的粪便、肠系膜和股前淋巴结（LN）中分离出的沙门氏菌的流行率、血清型、抗菌药物耐药表型和脉冲场凝胶电泳（PFGE）图谱。在一项前瞻性队列研究中，对来自四个未报告疫情农场（非疫情农场）的160头犊牛在农场和屠宰时进行了采样。此外，还收集了来自两个确诊暴发农场（疫情农场）的80头犊牛的屠宰样本。对所有样本应用沙门氏菌分离培养方案，对分离出的菌株进一步进行血清型鉴定、抗菌药物敏感性测试和PFGE分析。在非疫情农场中，沙门氏菌在0%（0/160）的农场粪便样本、3.7%（6/160）的屠宰粪便拭子、21.9%（35/160）的肠系膜淋巴结和0.6%（1/160）的股前淋巴结中被检出。在非疫情牛群中鉴定出的血清型包括鼠伤寒沙门氏菌、塞罗沙门氏菌、哈特福德沙门氏菌和纽波特沙门氏菌。大多数分离株（64.3%，27/42）表现出独特的多重耐药（MDR）表型，包括对超广谱头孢菌素耐药。疫情农场犊牛的屠宰粪便样本和股前淋巴结中沙门氏菌的流行率在数值上较高，但与无疫情农场的犊牛相比无显著差异。从疫情农场分离出的血清型包括海德堡沙门氏菌和鼠伤寒沙门氏菌，以及单相鼠伤寒沙门氏菌菌株4,5,12:i:-和4,12:i: -，这些菌株在人类中也被报道为高致病性。所有分离株（33/33）均表现出MDR表型。在两次疫情中从患病犊牛分离出的沙门氏菌菌株具有难以区分的PFGE图谱，表明存在农场间传播。此外，在屠宰时从该队列存活成员的三个股前淋巴结中分离出了导致犊牛疫情的海德堡沙门氏菌基因型。强烈建议实施宰前生物安全措施（限制人员和访客流动、车辆、鞋类和器具消毒），以降低农场中沙门氏菌的流行率并保障食品安全。
