Department of Food Hygiene and Control, Faculty of Veterinary Medicine, Cairo University, Giza, 12211, Egypt.
Department of Pathobiological Sciences, University of Wisconsin, Madison 53706; Department of Microbiology and Immunology, Faculty of Veterinary Medicine, Cairo University, Giza, 12211, Egypt.
J Dairy Sci. 2021 Jan;104(1):211-220. doi: 10.3168/jds.2020-18214. Epub 2020 Nov 6.
Nontuberculous mycobacteria (NTM) compose a group of mycobacteria that do not belong to the Mycobacterium tuberculosis complex group. They are frequently isolated from environmental samples such as water, soil, and, to a lesser extent, food samples. Isolates of NTM represent a major health threat to humans worldwide, especially those who have asthma or are immunocompromised. Human disease is acquired from environmental exposures and through consumption of NTM-contaminated food. The most common clinical manifestation of NTM disease in human is lung disease, but lymphatic, skin and soft tissue, and disseminated disease are also important. The main objective of the current study was to profile the farm-level contamination of cow milk with NTM by examining milk filters and bulk tank milk samples. Five different NTM species were isolated in one dairy herd in Wisconsin, with confirmed 16S rRNA genotypes including Mycobacterium fortuitum, Mycobacterium avium ssp. hominissuis, Mycobacterium abscessus, Mycobacterium simiae, and Mycobacterium avium ssp. paratuberculosis (Mycobacterium paratuberculosis). In tank milk samples, M. fortuitum was the predominant species in 48% of the samples, whereas M. chelonae/abscessus and M. fortuitum were the only 2 species obtained from 77 and 23% of the examined filters, respectively. Surprisingly, M. avium ssp. hominissuis, M. paratuberculosis, and M. simiae were isolated from 16.7, 10.4, and 4% of the examined milk samples, respectively, but not from milk filters. Interestingly, NTM isolates from human clinical cases in Wisconsin clustered very closely with those from milk samples. These findings suggest that the problem of NTM contamination is underestimated in dairy herds and could contribute to human infections with NTM. Overall, the study validates the use of bulk tank samples rather than milk filters to assess contamination of milk with NTM. Nontuberculous mycobacteria represent one type of pathogens that extensively contaminate raw milk at the farm level. The significance of our research is in evaluating the existence of NTM at the farm level and identifying a simple approach to examine the potential milk contamination with NTM members using tank milk or milk filters from dairy operations. In addition, we attempted to examine the potential link between NTM isolates found in the farm to those circulating in humans in Wisconsin.
非结核分枝杆菌（NTM）是一组不属于结核分枝杆菌复合体的分枝杆菌。它们经常从环境样本中分离出来，如水、土壤，以及在较小程度上，从食物样本中分离出来。NTM 分离株对全球人类健康构成重大威胁，尤其是那些患有哮喘或免疫功能低下的人。人类疾病是通过环境暴露和食用 NTM 污染的食物获得的。NTM 病在人类中最常见的临床表现是肺部疾病，但也包括淋巴、皮肤和软组织以及播散性疾病。目前研究的主要目的是通过检查牛奶过滤器和大容量奶罐奶样来描绘奶牛场牛奶中 NTM 的污染情况。在威斯康星州的一个奶牛场中分离到了 5 种不同的 NTM 种，经确认的 16S rRNA 基因型包括脓肿分枝杆菌、人型分枝杆菌、脓肿分枝杆菌、猿猴分枝杆菌和结核分枝杆菌（结核分枝杆菌）。在罐奶样中，48%的样本中优势种为脓肿分枝杆菌，而 M.chelonae/脓肿分枝杆菌和脓肿分枝杆菌是仅从 77%和 23%的检查过滤器中获得的 2 种物种。令人惊讶的是，人型分枝杆菌、结核分枝杆菌和猿猴分枝杆菌分别从 16.7%、10.4%和 4%的检查奶样中分离出来，但没有从奶过滤器中分离出来。有趣的是，从威斯康星州的人类临床病例中分离到的 NTM 分离株与从奶样中分离到的分离株非常相似。这些发现表明，奶牛场中 NTM 污染问题被低估了，可能导致人类感染 NTM。总的来说，该研究验证了使用大容量奶罐样本而不是奶过滤器来评估 NTM 污染奶的方法。非结核分枝杆菌是一种广泛污染农场一级生奶的病原体。我们研究的意义在于评估农场一级 NTM 的存在，并确定一种简单的方法来检查使用来自奶制品操作的大容量奶罐或奶过滤器检查 NTM 成员潜在的奶污染。此外，我们试图检查在农场中发现的 NTM 分离株与在威斯康星州循环的人类之间的潜在联系。
