Ragione R M La, Best A, Clifford D, Weyer U, Johnson L, Marshall R N, Marshall J, Cooley W A, Farrelly S, Pearson G R, Woodward M J
Department of Clinical Veterinary Science, University of Bristol Veterinary School, Langford, Bristol BS40 5DU, UK.
J Med Microbiol. 2006 Jul;55(Pt 7):819-828. doi: 10.1099/jmm.0.46469-0.
Escherichia coli O157 : H7 and Cryptosporidium parvum infections of man have been associated with direct contact with small ruminants. Colostrum protects neonates against gastrointestinal pathogens, and orphan lambs, which are common on petting farms, may be deprived of this protection. In a recent study, it was demonstrated that high shedding of E. coli O157 : H7 by an 8-week-old goat kid was associated with coincidental C. parvum infection. Furthermore, both pathogens were co-located in the distal gastrointestinal tract. It was hypothesized that colostrum deprivation and pre-infection with C. parvum predisposed young ruminants to colonization and increased shedding of E. coli O157 : H7. To test this, 21 lambs 5 weeks of age were divided into four groups as follows: (A) colostrum-deprived and inoculated with E. coli O157 : H7, (B) colostrum-deprived and inoculated with C. parvum and then E. coli O157 : H7, (C) conventionally reared and inoculated with E. coli O157 : H7, (D) conventionally reared and inoculated with C. parvum and then E. coli O157 : H7. C. parvum was detected between 8 and 12 days post-inoculation in most of the infected lambs. At 24 h post-inoculation with E. coli O157 : H7, all lambs were shedding between 5 x 10(4) and 5 x 10(7) c.f.u. E. coli O157 : H7 per gram of faeces. E. coli O157 : H7 was shed in higher numbers in the groups pre-inoculated with C. parvum, whether conventionally reared or colostrum-deprived. Interestingly, for the colostrum-deprived lambs on day 3, a significant difference in shedding of E. coli O157 : H7 was observed (P = 0.038), with the lambs inoculated with E. coli alone yielding higher counts than those pre-inoculated with C. parvum. From day 15 onwards, shedding of E. coli O157 : H7 was highest from the colostrum-deprived C. parvum-infected lambs, then (in descending order of shedding) the colostrum-deprived lambs, the conventionally reared lambs infected with C. parvum, and the conventionally reared animals. In total, four animals were euthanized, two at 24 h and two at 96 h post inoculation with E. coli O157 : H7 (two conventionally reared and two colostrum-deprived). All animals euthanized were from groups pre-inoculated with C. parvum prior to challenge with E. coli O157 : H7. On examination of tissues, in three of the four animals examined, multifocal attaching and effacing lesions were observed in the caecum, colon, rectum and at the recto-anal junction, and were confirmed by immunohistochemistry to be associated with E. coli O157 : H7.
人类感染大肠杆菌O157 : H7和微小隐孢子虫与直接接触小型反刍动物有关。初乳可保护新生儿抵御胃肠道病原体，而在宠物农场常见的孤儿羔羊可能会被剥夺这种保护。在最近一项研究中，已证明一只8周龄的山羊羔大量排出大肠杆菌O157 : H7与同时感染微小隐孢子虫有关。此外，两种病原体都位于远端胃肠道。据推测，初乳缺乏和先感染微小隐孢子虫使幼龄反刍动物易被大肠杆菌O157 : H7定植并增加其排出量。为验证这一点，将21只5周龄的羔羊分为四组如下：(A) 初乳缺乏并接种大肠杆菌O157 : H7；(B) 初乳缺乏并先接种微小隐孢子虫然后接种大肠杆菌O157 : H7；(C) 常规饲养并接种大肠杆菌O157 : H7；(D) 常规饲养并先接种微小隐孢子虫然后接种大肠杆菌O157 : H7。在大多数受感染羔羊接种后8至12天检测到微小隐孢子虫。在接种大肠杆菌O157 : H7后24小时，所有羔羊每克粪便排出大肠杆菌O157 : H7的菌落形成单位在5×10⁴至5×10⁷之间。无论常规饲养还是初乳缺乏，先接种微小隐孢子虫的组中大肠杆菌O157 : H7的排出量都更高。有趣的是，对于初乳缺乏的羔羊，在第3天观察到大肠杆菌O157 : H7排出量有显著差异（P = 0.038），仅接种大肠杆菌的羔羊排出量高于先接种微小隐孢子虫的羔羊。从第15天起，初乳缺乏且感染微小隐孢子虫的羔羊大肠杆菌O157 : H7排出量最高，然后（按排出量降序排列）是初乳缺乏的羔羊、感染微小隐孢子虫的常规饲养羔羊以及常规饲养的动物。总共对4只动物实施了安乐死，2只在接种大肠杆菌O157 : H7后24小时，2只在96小时（2只常规饲养，2只初乳缺乏）。所有实施安乐死的动物都来自在接种大肠杆菌O157 : H7之前先接种微小隐孢子虫的组。检查组织时，在4只检查的动物中的3只，在盲肠、结肠、直肠和直肠 - 肛门交界处观察到多灶性黏附性和抹消性病变，免疫组化证实与大肠杆菌O157 : H7有关。
