沙门氏菌侵入人体细胞的电镜图(Credit: Rocky Mountain Laboratories, NIAID, NIH)
近日，来自加州大学圣芭芭拉分校等处的研究者发明了一种检测高毒力沙门氏菌的方法，这为将来阻止食品受沙门氏菌感染提供了一定的检测方法。研究者相关的研究成果刊登在了近日的国际杂志PLoS Pathogen上。沙门氏菌是一种常见的可以引起院内感染以及食品中毒的常见致病菌，近几年因为沙门氏菌的感染给人类的健康影响和带来的经历负担越来越大。为此，研究者对高毒力沙门氏菌菌株进行研究，旨在找到一种检测方法来抵御这种细菌对食品的危害以及给畜牧业带来的风险。
来自芭芭拉分校以及悉尼大学的研究者组成了一个大的研究团队来进行高毒力沙门氏菌的研究，这些细菌分离自牲畜身上，而且用疫苗完全无效。细菌的行为就像是木马一样，只是在开始感染之后才展现其强大的致病武器，研究者Heithoff表示，这些菌株可持续感染，而且长达5年，它们在感染期间可以不断变化来引起不同形式的感染。研究者发明出了一种检测方法，可以快速检测并且从很多不同毒力的菌株中识别出高毒力的菌株。人们通常通过食用被污染的牛肉、鸡肉和鸡蛋引起沙门氏菌食物中毒，而且感染沙门氏菌的牲畜所排出的粪便也会污染蔬菜以及水果，这无疑是一种健康隐患。因为沙门氏菌的感染或者污染导致美国每年损失146亿美元。
高毒力的沙门氏菌对人类和动物的健康都构成威胁，必须引起研究者的高度重视，目前，研究者已经意识到了这种细菌引起的问题了，而且已经采取措施去制止这种细菌所引起的感染和疾病了。（生物谷：T.Shen编译）
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doi:10.1371/journal.ppat.1002647
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Intraspecies Variation in the Emergence of Hyperinfectious Bacterial Strains in Nature
Douglas M. Heithoff1#, William R. Shimp1#, John K. House2, Yi Xie3, Bart C. Weimer3, Robert L. Sinsheimer1, Michael J. Mahan1*
Salmonella is a principal health concern because of its endemic prevalence in food and water supplies, the rise in incidence of multi-drug resistant strains, and the emergence of new strains associated with increased disease severity. Insights into pathogen emergence have come from animal-passage studies wherein virulence is often increased during infection. However, these studies did not address the prospect that a select subset of strains undergo a pronounced increase in virulence during the infective process- a prospect that has significant implications for human and animal health. Our findings indicate that the capacity to become hypervirulent (100-fold decreased LD50) was much more evident in certain S. enterica strains than others. Hyperinfectious salmonellae were among the most virulent of this species; restricted to certain serotypes; and more capable of killing vaccinated animals. Such strains exhibited rapid (and rapidly reversible) switching to a less-virulent state accompanied by more competitive growth ex vivo that may contribute to maintenance in nature. The hypervirulent phenotype was associated with increased microbial pathogenicity (colonization; cytotoxin production; cytocidal activity), coupled with an altered innate immune cytokine response within infected cells (IFN-β; IL-1β; IL-6; IL-10). Gene expression analysis revealed that hyperinfectious strains display altered transcription of genes within the PhoP/PhoQ, PhoR/PhoB and ArgR regulons, conferring changes in the expression of classical virulence functions (e.g., SPI-1; SPI-2 effectors) and those involved in cellular physiology/metabolism (nutrient/acid stress). As hyperinfectious strains pose a potential risk to human and animal health, efforts toward mitigation of these potential food-borne contaminants may avert negative public health impacts and industry-associated losses.
