Farm Animal and Veterinary Public Health, Faculty of Veterinary Science, University of Sydney, 425 Werombi Rd, Camden, NSW 2570, Australia.
Vet Microbiol. 2011 Jan 10;147(1-2):127-32. doi: 10.1016/j.vetmic.2010.06.016. Epub 2010 Jun 19.
Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's disease or paratuberculosis, a chronic enteritis of ruminants, and has been suggested to play a role in Crohn's disease in humans. While Johne's disease is primarily expressed in the gastrointestinal tract, isolation of MAP from extra-intestinal tissues indicates that microbial dissemination via the haematogenous route may occur during the infection. Consequently, the occurrence of mycobacteraemia and dissemination to the liver and hepatic lymph node was investigated in 111 sheep. Disseminated infection was detected in 18 of the 53 sheep that were confirmed to be infected following oral exposure to MAP while the bacterium was isolated from the blood of only 4 of these animals. Disseminated infection was detected more frequently from animals with a positive compared to a negative faecal culture result, multibacillary compared to paucibacillary lesions, and clinical compared to subclinical disease. Detection of MAP in blood by culture was significantly associated with increased time post-exposure and clinical disease, with trends for increased detection in animals with multibacillary lesions and positive faecal culture results. Isolation of MAP from blood was difficult in the early stages of the disease and in paucibacillary animals as the bacteraemia may be intermittent, below the limit of detection or MAP may be present in a dormant non-culturable form. Prolonged incubation periods prior to growth in BACTEC were consistent with inhibition of growth or dormancy in some blood cultures.
分支杆菌亚种副结核分枝杆菌（MAP）是引起约翰氏病或副结核病的病原体，是反刍动物的一种慢性肠炎，并且有人认为它在人类克罗恩病中起作用。虽然约翰氏病主要在胃肠道中表达，但从肠外组织中分离出 MAP 表明，在感染过程中，微生物可能通过血流途径传播。因此，研究了 111 只绵羊中菌血症的发生和向肝脏和肝淋巴结的扩散。在 53 只经口暴露于 MAP 后被确认为感染的绵羊中，有 18 只出现了弥散性感染，而只有 4 只动物的血液中分离出该细菌。与粪便培养阴性的动物相比，具有阳性粪便培养结果、多病灶与少病灶、临床与亚临床疾病的动物中，更频繁地检测到弥散性感染。通过培养从血液中检测到 MAP 与暴露后时间增加和临床疾病显著相关，在多病灶和阳性粪便培养结果的动物中，检测到的趋势增加。在疾病的早期和少病灶动物中，从血液中分离 MAP 较为困难，因为菌血症可能是间歇性的，低于检测限，或者 MAP 可能以休眠的非可培养形式存在。在 BACTEC 中生长之前的延长孵育期与某些血液培养物中的生长抑制或休眠一致。
