质粒编码菌毛和紧密素对兔特异性肠致病性大肠杆菌黏附和定殖于兔肠道能力的作用。
Contribution of plasmid-encoded fimbriae and intimin to capacity of rabbit-specific enteropathogenic Escherichia coli to attach to and colonize rabbit intestine.
作者信息
Krejany E O, Grant T H, Bennett-Wood V, Adams L M, Robins-Browne R M
机构信息
Department of Microbiology and Immunology, University of Melbourne, Victoria 3052, Australia.
出版信息
Infect Immun. 2000 Nov;68(11):6472-7. doi: 10.1128/IAI.68.11.6472-6477.2000.
Attachment to the intestinal mucosa is an essential step in the pathogenesis of diarrhea caused by enteropathogenic Escherichia coli (EPEC). Fimbriae and intimin, the outer membrane protein product of the chromosomal eae gene, contribute to this process, but their relative roles and the nature of their interaction are not known. The aim of this study was to determine the relative contribution of plasmid-encoded fimbriae, termed Ral, and intimin to the capacity of rabbit-specific EPEC (REPEC) to attach to the intestinal mucosa of rabbits. To achieve this, we constructed a series of mutants in REPEC strain 83/39 (O15:H-), in which the ralE and eae genes were insertionally inactivated. These strains were then inoculated into ligated loops of rabbit ileum, which were resected 18 h later and examined by light and electron microscopy. The results showed that intimin, but not Ral, is essential for the elicitation of attaching-effacing lesions by REPEC. Nevertheless, a delta eae Ral-bearing mutant adhered to the intestinal epithelium to the same extent as its eae-positive parent and far more extensively than an eae(+) delta ral strain. To examine the contribution of Ral and intimin to colonization of rabbit intestine, we fed these strains to weanling rabbits, which were killed 4 days later, so that the number of bacteria in various regions of the intestine could be determined. The results indicated that strain 83/39 requires both Ral and intimin to colonize the intestine successfully and that a delta eae delta ralE double mutant was incapable of colonizing the intestine. Taken together, these findings indicate that Ral and intimin act independently as adhesion factors of REPEC strain 83/39 and that this strain carries no other significant colonization factor. When both Ral and intimin are present, they appear to act cooperatively, with Ral-mediated adhesion preceding that mediated by intimin.
黏附于肠道黏膜是肠致病性大肠杆菌（EPEC）所致腹泻发病机制中的一个关键步骤。菌毛和紧密素（染色体eae基因的外膜蛋白产物）参与了这一过程，但其相对作用及相互作用的性质尚不清楚。本研究旨在确定质粒编码菌毛Ral和紧密素对兔特异性EPEC（REPEC）黏附兔肠道黏膜能力的相对贡献。为此，我们构建了REPEC 83/39菌株（O15:H-）的一系列突变体，其中ralE和eae基因被插入失活。然后将这些菌株接种到兔回肠的结扎肠袢中，18小时后切除肠袢，通过光镜和电镜检查。结果表明，紧密素而非Ral对于REPEC引发黏附-抹去性损伤至关重要。然而，一株携带Δeae Ral的突变体与eae阳性亲本一样能在相同程度上黏附肠上皮，且比eae(+)Δral菌株黏附得更广泛。为了研究Ral和紧密素对兔肠道定植的贡献，我们将这些菌株喂给断奶幼兔，4天后处死幼兔，以便确定肠道各区域的细菌数量。结果表明，83/39菌株成功定植肠道需要Ral和紧密素两者，且ΔeaeΔralE双突变体无法在肠道定植。综上所述，这些发现表明Ral和紧密素作为REPEC 83/39菌株的黏附因子独立发挥作用，且该菌株不携带其他重要的定植因子。当Ral和紧密素都存在时，它们似乎协同发挥作用，Ral介导的黏附先于紧密素介导的黏附。
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