Comparison of the contributions of heat-labile enterotoxin and heat-stable enterotoxin b to the virulence of enterotoxigenic Escherichia coli in F4ac receptor-positive young pigs
Comparison of the contributions of heat-labile enterotoxin and heat-stable enterotoxin b to the virulence of enterotoxigenic Escherichia coli in F4ac receptor-positive young pigs
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DOI：
10.1128/iai.01743-07
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发表时间：
2008-07-01
影响因子：
3.1
通讯作者：
Moxley, Rodney A.
中科院分区：
文献类型：
--
作者：
Erume, Joseph;Berberov, Emil A.;Moxley, Rodney A.
在猪中，最常见和最严重的产肠毒素大肠杆菌(ETEC)感染是由表达K88(F4)(+)菌毛、不耐热肠毒素(LT)、耐热肠毒素b(STB)和肠聚集性大肠杆菌热稳定毒素1的菌株引起的。先前的研究基于将肠毒素基因克隆到非产毒菌毛菌株中的设计，表明LT而不是STB在1周龄仔猪脱水腹泻病中发挥重要作用，研究设计包括构建等基因单缺失和双缺失突变体，并接种9日龄F4ac受体阳性的生物识别仔猪。根据接种后单位重量百分比变化和血清碳酸氢盐浓度，STB突变体(Delta EltAB)的毒力与亲本没有显著差异。然而，在STB-突变体中LT基因(Delta EltAB)的缺失导致接种猪的体重减轻、脱水和代谢性酸中毒完全消除，LT互补恢复了该菌株的毒力。这些结果支持这一假设，即LT比STB对F4(+)ETEC感染F4(+)ETEC在不到2周大的F4ac受体阳性仔猪中的毒力有更大的贡献。然而，与先前对共生仔猪的研究相比，没有证据表明LT的表达增强了W ETEC菌株在小肠的定植能力。
In swine, the most common and severe enterotoxigenic Escherichia coli (ETEC) infections are caused by strains that express K88 (F4)(+) fimbriae, heat-labile enterotoxin (LT), heat-stable enterotoxin b (STb), and enteroaggregative E. coli heat-stable toxin 1. Previous studies based on a design that involved enterotoxin genes cloned into a nontoxigenic fimbriated strain have suggested that LT but not STb plays an important role in dehydrating diarrheal disease in piglets 1 week old with a study design that involved construction of isogenic single- and double-deletion mutants and inoculation of 9-day-old F4ac receptor-positive gnotobiotic piglets. Based on the postinoculation percent weight change per It and serum bicarbonate concentrations, the virulence of the STb- mutant (Delta eltAB) did not significantly differ from that of the parent. However, deletion of the LT genes (Delta eltAB) in the STb- mutant resulted in a complete abrogation of weight loss, dehydration, and metabolic acidosis in inoculated pigs, and LT complementation restored the virulence of this strain. These results support the hypothesis that LT is a more significant contributor than STb to the virulence of F4(+) ETEC infections in young F4ac receptor-positive pigs less than 2 weeks old. However, in contrast to previous studies with gnotobiotic piglets, there was no evidence that the expression of LT enhanced the ability of the W ETEC strain to colonize the small intestine.