Peterz Mats, Butot Sophie, Jagadeesan Balamurugan, Bakker Douwe, Donaghy John
Nestlé Research Center, Nestec Ltd., Lausanne, Switzerland
Nestlé Research Center, Nestec Ltd., Lausanne, Switzerland.
Appl Environ Microbiol. 2016 Apr 18;82(9):2800-2808. doi: 10.1128/AEM.04042-15. Print 2016 May.
The efficiency of direct steam injection (DSI) at 105 °C for 3 s to inactivate Mycobacterium avium subsp. paratuberculosis in milk at a pilot-plant scale was investigated. Milk samples were artificially contaminated with M. avium subsp. paratuberculosis and also with cow fecal material naturally infected with M. avium subsp. paratuberculosis. We also tested milk artificially contaminated with Mycobacterium smegmatis as a candidate surrogate to compare thermal inactivation between M. smegmatis and M. avium subsp. paratuberculosis. Following the DSI process, no viable M. avium subsp. paratuberculosis or M. smegmatis was recovered using culture methods for both strains. For pure M. avium subsp. paratuberculosis cultures, a minimum reduction of 5.6 log10 was achieved with DSI, and a minimum reduction of 5.7 log10 was found with M. smegmatis. The minimum log10 reduction for wild-type M. avium subsp. paratuberculosis naturally present in feces was 3.3. In addition, 44 dairy and nondairy powdered infant formula (PIF) ingredients used during the manufacturing process of PIF were tested for an alternate source for M. avium subsp. paratuberculosis and were found to be negative by quantitative PCR (qPCR). In conclusion, the results obtained from this study indicate that a >7-fold-log10 reduction of M. avium subsp. paratuberculosis in milk can be achieved with the applied DSI process.
M. avium subsp. paratuberculosis is widespread in dairy herds in many countries. M. avium subsp. paratuberculosis is the causative agent of Johne's disease in cattle, and infected animals can directly or indirectly (i.e., fecal contamination) contaminate milk. Despite much research and debate, there is no conclusive evidence that M. avium subsp. paratuberculosis is a zoonotic bacterium, i.e., one that causes disease in humans. The presence of M. avium subsp. paratuberculosis or its DNA has been reported in dairy products, including pasteurized milk, cheese, and infant formula. In light of this, it is appropriate to evaluate existing mitigation measures to inactivate M. avium subsp. paratuberculosis in dairy products. The work conducted in this study describes the efficacy of direct steam injection, a thermal process commonly used in the dairy industry, to eliminate M. avium subsp. paratuberculosis and a surrogate bacterium in milk, thus ensuring the absence of M. avium subsp. paratuberculosis in dairy products subject to these process conditions.
研究了在中试规模下，105℃直接蒸汽注入（DSI）3秒对牛奶中副结核分枝杆菌的灭活效率。牛奶样品被副结核分枝杆菌人工污染，也被自然感染副结核分枝杆菌的牛粪污染。我们还测试了被耻垢分枝杆菌人工污染的牛奶，作为候选替代菌，以比较耻垢分枝杆菌和副结核分枝杆菌之间的热灭活情况。经过DSI处理后，两种菌株采用培养方法均未检出存活的副结核分枝杆菌或耻垢分枝杆菌。对于纯副结核分枝杆菌培养物，DSI可实现至少5.6 log10的减少，耻垢分枝杆菌至少减少5.7 log10。粪便中天然存在的野生型副结核分枝杆菌的最小log10减少量为3.3。此外，对婴儿配方奶粉（PIF）生产过程中使用的44种乳制品和非乳制品粉末状婴儿配方奶粉成分进行了检测，以寻找副结核分枝杆菌的替代来源，通过定量PCR（qPCR）检测发现均为阴性。总之，本研究结果表明，应用DSI工艺可使牛奶中的副结核分枝杆菌减少>7个log10。
副结核分枝杆菌在许多国家的奶牛群中广泛存在。副结核分枝杆菌是牛约翰氏病的病原体，感染动物可直接或间接（即粪便污染）污染牛奶。尽管进行了大量研究和辩论，但尚无确凿证据表明副结核分枝杆菌是一种人畜共患病细菌，即一种能在人类中引起疾病的细菌。在包括巴氏杀菌牛奶、奶酪和婴儿配方奶粉在内的乳制品中已报告了副结核分枝杆菌或其DNA的存在。有鉴于此，评估现有灭活乳制品中副结核分枝杆菌的缓解措施是恰当的。本研究开展的工作描述了直接蒸汽注入（一种乳制品行业常用的热处理方法）消除牛奶中副结核分枝杆菌和一种替代细菌的效果，从而确保在这些工艺条件下的乳制品中不存在副结核分枝杆菌。
