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首页> 外文期刊>Infection and immunity >Enhanced Virulence of the Escherichia coli O157:H7 Spinach-Associated Outbreak Strain in Two Animal Models Is Associated with Higher Levels of Stx2 Production after Induction with Ciprofloxacin
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Enhanced Virulence of the Escherichia coli O157:H7 Spinach-Associated Outbreak Strain in Two Animal Models Is Associated with Higher Levels of Stx2 Production after Induction with Ciprofloxacin

机译：在两种动物模型中大肠杆菌O157：H7菠菜相关暴发株的增强毒力与环丙沙星诱导后更高的Stx2生产水平相关

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Shiga toxin (Stx)-producing Escherichia coli (STEC) causes hemorrhagic colitis and the hemolytic-uremic syndrome (HUS). STEC strains may produce Stx1a and/or Stx2a or variants of either toxin. A 2006 spinach-associated outbreak of STEC O157:H7 resulted in higher hospitalization and HUS rates than previous STEC outbreaks. The spinach isolate, strain K3995, contains both stx2a and stx2c. We hypothesized that the enhanced virulence of K3995 reflects the combination of stx2 alleles (carried on lysogenic phages) and/or the amount of Stx2 made by that strain. We compared the virulence of K3995 to those of other O157:H7 isolates and an isogenic Stx2 mutant in rabbits and mice. We also measured the relative levels of Stx2 produced from those strains with or without induction of the stx-carrying phage. Some rabbits infected with K3995 exhibited intestinal pathology and succumbed to infection, while none of those infected with O157:H7 strain 2812 (Stx1a+ Stx2a+) died or showed pathological signs. Rabbits infected with the isogenic Stx2a mutant K3995 stx2a::cat were not colonized as well as those infected with K3995 and exhibited no signs of disease. In the streptomycin-treated mouse model, more animals infected with K3995 died than did those infected with O157:H7 strain 86-24 (Stx2a+). Additionally, K3995 produced higher levels of total Stx2 and toxin phage DNA in cultures after phage induction than did 86-24. Our results demonstrate the greater virulence of K3995 compared to other O157:H7 strains in rabbits and mice. We conclude that this enhanced virulence is linked to higher levels of Stx2 expression as a consequence of increased phage induction.
机译：产生志贺毒素（Stx）的大肠杆菌（STEC）导致出血性结肠炎和溶血性尿毒症综合征（HUS）。 STEC菌株可能产生Stx1a和/或Stx2a或任何毒素的变体。 2006年与菠菜相关的STEC O157：H7暴发导致住院和HUS发病率高于以前的STEC暴发。菠菜分离株K3995包含 stx 2a 和 stx 2c 。我们假设K3995的增强毒力反映了 stx 2 等位基因（在溶原性噬菌体上携带）和/或该菌株产生的Stx2数量的组合。我们将K3995的毒力与其他O157：H7分离株的毒力以及同基因的Stx2突变体在兔和小鼠中进行了比较。我们还测量了由带有或不带有 stx 的噬菌体诱导的菌株产生的Stx2的相对水平。一些感染了K3995的兔子表现出肠道病理并死于感染，而感染O157：H7菌株2812（Stx1a + Stx2a + ）的兔子均没有死亡或出现病理征象。同基因Stx2a突变体K3995 stx 2a :: cat 感染的兔子没有被感染，也没有感染K3995的兔子。 。在链霉素治疗的小鼠模型中，感染K3995的动物比感染O157：H7株86-24（Stx2a + ）的动物要多。另外，在噬菌体诱导后，K3995在培养物中产生的总Stx2和毒素噬菌体DNA的水平高于86-24。我们的结果表明，与其他O157：H7株相比，K3995在兔和小鼠中的毒力更高。我们得出结论，由于噬菌体诱导增加，这种增强的毒力与更高水平的Stx2表达有关。

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