Differences in virulence among Escherichia coli O157: H7 strains isolated from humans during disease outbreaks and from healthy cattle
Differences in virulence among Escherichia coli O157: H7 strains isolated from humans during disease outbreaks and from healthy cattle
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DOI：
10.1128/aem.00755-07
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发表时间：
2007-11-01
影响因子：
4.4
通讯作者：
Francis, David H.
中科院分区：
文献类型：
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作者：
Baker, Diane R.;Moxley, Rodney A.;Francis, David H.
大肠杆菌O157:H7会在人类中引发危及生命的腹泻、出血性结肠炎和溶血性尿毒综合征的暴发，给农业造成重大经济损失，并且可能成为生物恐怖主义的潜在媒介。尽管大肠杆菌O157:H7在牛以及人类经常接触的其他物种中的流行率很高，但人类感染相对不常见，尽管其感染剂量很低。对疾病发病率低的一个合理解释是，可能并非所有菌株对人类都有致病性。如果自然界中菌株之间的致病性存在显著差异，那么人类疾病可能会筛选出高致病性菌株。我们使用无菌仔猪模型来研究从健康牛以及疾病暴发中的人类分离出的菌株的致病性，并确定志贺毒素1（Stx1）和志贺毒素2（Stx2）的产生与致病性之间的相关性。总体而言，从健康牛分离出的大肠杆菌O157:H7菌株在无菌仔猪中的致病性比从疾病暴发中的人类分离出的菌株弱。大肠杆菌O157:H7菌株产生的Stx2的量与菌株致病性相关，这通过仔猪存活率降低以及因脑梗死导致的中枢神经系统疾病症状来衡量。在培养物中产生的Stx1的量与仔猪存活时间长短或中枢神经系统疾病症状无关。我们认为，疾病暴发会在动物排出的大肠杆菌O157:H7菌株中筛选出高水平Stx2的产生者，并且进一步认为Stx1的表达在人类疾病暴发中不太可能起重要作用。
Escherichia coli O157:H7 causes life-threatening outbreaks of diarrhea, hemorrhagic colitis, and hemolytic-uremic syndrome in humans and significant economic loss in agriculture and could be a potential agent of bioterrorism. Although the prevalence of E. coli O157:H7 in cattle and other species with which humans have frequent contact is high, human infections are relatively uncommon, despite a low infectious dose. A plausible explanation for the low disease incidence is the possibility that not all strains are virulent in humans. If there are substantial differences in virulence among strains in nature, then human disease may select for high virulence. We used a gnotobiotic piglet model to investigate the virulence of isolates from healthy cattle and from humans in disease outbreaks and to determine the correlation between production of Shiga toxin 1 (Stx1) and Stx2 and virulence. Overall, E. coli O157:H7 strains isolated from healthy cattle were less virulent in gnotobiotic piglets than strains isolated from humans during disease outbreaks. The amount of Stx2 produced by E. coli O157:H7 strains correlated with strain virulence as measured by a reduction in piglet survival and signs of central nervous system disease due to brain infarction. The amount of Stx1 produced in culture was not correlated with the length of time of piglet survival or with signs of central nervous system disease. We suggest that disease outbreaks select for producers of high levels of Stx2 among E. coli O157:H7 strains shed by animals and further suggest that Stx1 expression is unlikely to be significant in human outbreaks.