Pearson Melanie M, Mobley Harry L T
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-0620, USA.
J Med Microbiol. 2007 Oct;56(Pt 10):1277-1283. doi: 10.1099/jmm.0.47314-0.
The Gram-negative enteric bacterium Proteus mirabilis is a frequent cause of urinary tract infections (UTIs) in individuals with long-term indwelling catheters or with complicated urinary tracts. The recent release of the P. mirabilis strain HI4320 genome sequence has facilitated identification of potential virulence factors in this organism. Genes appearing to encode a type III secretion system (TTSS) were found in a low GC-content pathogenicity island in the P. mirabilis chromosome. This island contains 24 intact genes that appear to encode all components necessary to assemble a TTSS needle complex, plus at least two putative secreted effector proteins and their chaperones. The genetic organization of the TTSS genes is very similar to that of the TTSS of Shigella flexneri. RT-PCR analysis indicated that these genes are expressed at low levels in vitro. However, insertional mutation of two putative TTSS genes, encoding the requisite ATPase and a possible negative regulator, resulted in no change in either the growth rate of the mutant or the secreted protein profile compared to wild-type. Furthermore, there was no difference in quantitative cultures of urine, bladder and kidney between the ATPase mutant and the wild-type strain in the mouse model of ascending UTI in either independent challenge or co-challenge experiments. The role of the P. mirabilis TTSS, if any, is yet to be determined.
革兰氏阴性肠道细菌奇异变形杆菌是长期留置导尿管或患有复杂尿路疾病的个体发生尿路感染（UTI）的常见原因。奇异变形杆菌HI4320菌株基因组序列的最近公布有助于鉴定该生物体中的潜在毒力因子。在奇异变形杆菌染色体的低GC含量致病岛中发现了似乎编码III型分泌系统（TTSS）的基因。该岛包含24个完整基因，这些基因似乎编码组装TTSS针状复合物所需的所有成分，以及至少两种推定的分泌效应蛋白及其伴侣蛋白。TTSS基因的遗传组织与弗氏志贺菌的TTSS非常相似。RT-PCR分析表明，这些基因在体外低水平表达。然而，与野生型相比，编码必需ATP酶和一种可能的负调节因子的两个推定TTSS基因的插入突变在突变体的生长速率或分泌蛋白谱方面均未导致变化。此外，在独立攻击或联合攻击实验中，在上升性UTI小鼠模型中，ATP酶突变体和野生型菌株在尿液、膀胱和肾脏的定量培养方面没有差异。奇异变形杆菌TTSS的作用（如果有的话）尚待确定。
