应激实验证明沙门氏菌是“一块硬骨头”

沙门氏菌是非常重要的食物源性病原体，但其在环境中生存繁衍的机制尚未完全清楚。本次美国西部禽病大会上，来自加州大学兽医学院的Bart Weiner就沙门氏菌如何存活及如何减少其含量的问题做了有关报告。

沙门氏菌有一套有效的机制来保证其在环境中存活并繁衍，能引起人类肠道疾病，对酸、过氧化物、热和高渗透环境都有抵抗性。最近Weiner和他的同事试图研究环境压力对沙门氏菌存活率的影响，为降低沙门氏菌含量寻找新的方法。

冷和酸的应激试验

在最初的实验中，专家们假设从动物宿主到自然环境的转移过程中，沙门氏菌能够在低温中存活很长时间。试验结果表明，沙门氏菌可以在低温中存活336小时，在这段时间内，48小时后存活率有所降低；然而在5摄氏度时，240小时后仍然存在大量活菌。沙门氏菌在过氧化物、高渗液体、酸环境中，分别于0.5小时后和5小时后对其采样，结果显示只有过氧化物能够显著降低其存活率。

另外，研究者还用6种益生元、5种益生菌对沙门氏菌存活率进行实验。每种益生元对沙门氏菌存活率，及其对宿主细胞的粘附力的影响都各不相同。比如，有一种MOS（甘露寡糖）会特异性地增强伤寒沙门氏菌对宿主细胞的粘附性。研究者还添加乳酸菌，检测沙门氏菌粘附性是否降低，结果显示，双歧杆菌可以降低沙门氏菌对上皮细胞的粘附力。

这些关于沙门氏菌抗压机制的新发现，有助于减少沙门氏菌活体污染环境，进一步减少沙门氏菌对人类和动物感染和疫情爆发。该研究全文已发表于应用环境微生物学杂志（Applied and Environmental Microbiology）。

据悉:北京磐石顶冠动物药业有限公司出品的“健体宝”含高酶双歧活芽胞杆菌、乳酸菌、活菌总数高达≥2x10⁸CFU/g。

因此：笔者建议在日常种鸽保健护理时，定期添加北京磐石顶冠动物药业公司出品的“健体宝”和“智慧油”拌料湿喂，可减少种鸽感染沙门氏菌的感染发病几率。

Stress treatments show that Salmonella is a tough cookie

Salmonella is an important food born pathogen but its mechanisms to survive in the environment are still partly unclear. Speaking at the Western Poultry Disease Conference (WPDC), Bart Weiner from the School of Veterinary Medicine, University of California presented new work on how Salmonella enteritidis survival can be reduced.

Salmonella have efficient mechanisms to survive processing and persist in the environment to cause gastrointestinal disease in humans. Salmonella are well document to survive acid, peroxide, osmotic and heat stress with many of the genes responsible for the survival well defined. In the recent work from Weiner and his collegues they wanted to examine the way environmental stress influenced the survival rate of Salmonella and find novel ways - such as adding pre- and probiotics - to reduce the survival rate of this bacterium.

Cold and acid stress

The initial experiment examined the ability of Salmonella to survive cold stress for at least 336 hours to test the hypothesis that Salmonella can withstand long periods of exposure to low temperatures during the transition between animal hosts and the environment. It was shown that Salmonella survived cold stress for at least 336 hours. During the time course, survival declined after 48 hours, while at 5 degress Celcius a significantly high number of viable bacteria were observed after 240 hours. Exposure to peroxide, osmotoc and acid for 0.5 hours (shock) and 5 hours (stress) was examined to find that only peroxide shock significanlty reduced survival.

Feed additives

Next to the stress treatments, the research team examined six prebiotic and five probiotic treatments. A dose response was observed with each prebiotic, but each treatment had an unique effect on Salmonella adhesion of stressed cells. For example, a certain MOS type encouraged adesion of Salmonella enteriditis beyond that of the control. Addition of probiotic lactic acid bacteria was tested to reduce adhesion. Bifidobacterium infantis was shown to have a beneficial effect on epithelial cells.

These new insights in the underlying mechanisms os stress resistance and host association will provide additional strategies to further reduce Salmonella viability to limit transmit in the environment and reduce infections and further outbreaks of Salmonella in the animal and human population. This research will be published as a full paper in the journal: Applied and Environmental Microbiology.

The Western Poultry Disease Conference is beng held for the 60th time and takes place in Sacramento, California, from 20 till 23 March.