Lipopolysaccharide O-antigen of enterohemorrhagic Escherichia coli O157:H7 is required for killing both insects and mammals
Lipopolysaccharide O-antigen of enterohemorrhagic Escherichia coli O157:H7 is required for killing both insects and mammals
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DOI：
10.1111/j.1574-6968.2012.02599.x
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发表时间：
2012-08-01
影响因子：
2.1
通讯作者：
Kaito, Chikara
中科院分区：
文献类型：
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作者：
Miyashita, Atsushi;Iyoda, Sunao;Kaito, Chikara
使用哺乳动物研究肠出血性大肠杆菌（EHEC）感染机制需要大量的动物，既昂贵又与伦理问题有关。在此，我们评估了EHEC在家蚕模型中的致病机制。将临床分离的EHEC O 157：H7 Sakai注射到蚕血淋巴或小鼠腹腔液中可杀死宿主动物。肠出血性大肠杆菌O 157：H7 Sakai的rfbE基因缺失突变体（编码perosamine合成酶，O-抗原的单糖组分合成酶）或waaL基因缺失突变体（编码针对脂多糖（LPS）的脂质A-核心区域的O-抗原连接酶）在蚕和小鼠中的杀伤能力减弱。将rfbE基因或waaL基因导入相应的突变体中恢复了蚕的杀伤能力。家蚕血淋巴中的一种主要抗菌肽moricin抑制了两种突变体的生长。在猪血清中，两种突变体的活力均降低。猪血清对这两种突变体的杀菌作用通过热处理被灭活。这些结果表明，EHEC O 157：H7的LPS O抗原对宿主体液中的抗菌因子起着重要的防御作用，因此是EHEC在动物中致死效应所必需的。
Studies of enterohemorrhagic Escherichia coli (EHEC) infection mechanisms using mammals require large numbers of animals and are both costly and associated with ethical problems. Here, we evaluated the pathogenic mechanisms of EHEC in the silkworm model. Injection of a clinically isolated EHEC O157:H7 Sakai into either the silkworm hemolymph or intraperitoneal fluid of mice killed the host animals. EHEC O157:H7 Sakai deletion mutants of the rfbE gene, which encodes perosamine synthetase, a monosaccharide component synthetase of the O-antigen, or deletion mutants of the waaL gene, which encodes O-antigen ligase against the lipid A-core region of lipopolysaccharide (LPS), had attenuated killing ability in both silkworms and mice. Introduction of the rfbE gene or the waaL gene into the respective mutants restored the killing ability in silkworms. Growth of both mutants was inhibited by a major antimicrobial peptide in the silkworm hemolymph, moricin. The viability of both mutants was decreased in swine serum. The bactericidal effect of swine serum against both mutants was inactivated by heat treatment. These findings suggest that the LPS O-antigen of EHEC O157:H7 plays an important defensive role against antimicrobial factors in the host body fluid and is thus essential to the lethal effects of EHEC in animals.