Alberta Agriculture and Rural Development, Agriculture Centre, 100, 5401-1st Avenue South, Lethbridge, Alberta, Canada T1J 4V6.
J Anim Sci. 2011 Jan;89(1):237-44. doi: 10.2527/jas.2010-3088. Epub 2010 Sep 17.
Super-shedders, cattle shedding at least 10(4) cfu of Escherichia coli O157:H7 per gram of feces, increase the risks of contaminating the food chain and disseminating the organism through cattle populations. Because detecting super-shedders in cattle populations is laborious and time-consuming, a study was conducted to evaluate the role of hide and pen-floor contamination by model super shedders (MSS) in transmission of E. coli O157:H7. Steers (n = 48) negative for E. coli O157:H7 were allocated to 6 pens, with 2 replicate pens per treatment. Treatment A consisted of 3,000 g of feces inoculated with 10(6) cfu/g of a 5-strain mixture of nalidixic acid-resistant E. coli O157:H7 and spread in simulated fecal pats on the pen floor for d 0 through 4 and d 14 through 18. For treatment B, 100 g of the feces per day was spread on the perineum of 1 MSS per pen, and the remaining feces was placed on the pen floor as fecal pats similar to treatment A. Treatment C differed from B in that 50 g of feces was spread on the perineum and 50 g on the brisket of the MSS steer. Fecal samples, perineal swabs (500-cm(2) area around the anus), freshly voided fecal pats and manila rope samples were collected during a 56-d experimental period. More positive rope samples were found in treatments B and C compared with A (P = 0.05), and steers within treatments B and C were 1.3 times more likely (P = 0.05) to shed E. coli O157:H7 in their feces than steers in treatment A. Even though the number of E. coli O157:H7 introduced into pens was similar, results indicate an increased importance of hide compared with pen-floor contamination for transmission of this organism to cattle. Because cattle within treatment B were persistently colonized with E. coli O157:H7, this design should prove suitable for future studies investigating the role of super-shedders in the transmission of E. coli O157:H7.
超级传播者,每克粪便中至少排出 10(4) 个大肠杆菌 O157:H7 菌落形成单位,增加了污染食物链和通过牛群传播该生物体的风险。由于在牛群中检测超级传播者既费力又费时,因此进行了一项研究,以评估模型超级传播者(MSS)的皮毛和栏地板污染对大肠杆菌 O157:H7 传播的作用。选择 48 头大肠杆菌 O157:H7 阴性的阉牛,将其分配到 6 个栏中,每个处理 2 个重复栏。处理 A 由 3000 g 接种了 10(6) cfu/g 的 5 株耐萘啶酸大肠杆菌 O157:H7 混合物的粪便组成,在栏地板上模拟粪便斑中散布粪便,时间为 d 0 至 4 和 d 14 至 18。对于处理 B,每天将 100 g 粪便散布在每个栏的 1 头 MSS 的会阴部,其余的粪便作为类似于处理 A 的粪便斑散布在栏地板上。处理 C 与 B 的不同之处在于,将 50 g 粪便散布在 MSS 牛的会阴部,将 50 g 粪便散布在牛的胸部。在 56 天的实验期间收集粪便样本、会阴拭子(肛门周围 500cm(2) 区域)、新鲜排出的粪便斑和马尼拉绳索样本。与处理 A 相比,在处理 B 和 C 中发现更多的阳性绳索样本(P = 0.05),并且处理 B 和 C 中的牛比处理 A 中的牛更有可能(P = 0.05)在粪便中排出大肠杆菌 O157:H7。尽管引入栏中的大肠杆菌 O157:H7 数量相似,但结果表明与栏地板污染相比,皮毛污染对该生物体传播给牛的重要性增加。由于处理 B 中的牛持续定植大肠杆菌 O157:H7,因此这种设计应适合未来研究超级传播者在大肠杆菌 O157:H7 传播中的作用。