Type 1 fimbriae and extracellular polysaccharides are preeminent uropathogenic Escherichia coli virulence determinants in the murine urinary tract
Type 1 fimbriae and extracellular polysaccharides are preeminent uropathogenic Escherichia coli virulence determinants in the murine urinary tract
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DOI：
10.1046/j.1365-2958.2002.03078.x
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发表时间：
2002-08-01
影响因子：
3.6
通讯作者：
Donnenberg, MS
中科院分区：
文献类型：
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作者：
Bahrani-Mougeot, FK;Buckles, EL;Donnenberg, MS
大肠杆菌是尿路感染 (UTI) 的主要原因。尽管许多细菌因素与尿路致病性大肠杆菌 (UPEC) 有关，但在动物模型中很少有此类因素被证明是尿路感染所必需的。先前对尿毒力因子的研究依赖于表型特征的事先鉴定。我们使用特征标记诱变 (STM) 来公正地鉴定对 UPEC 在小鼠泌尿道内生存至关重要的基因。使用携带 92 个独特标签的 mini-Tn5km2 构建了原型 UPEC 菌株 CFT073 的 2049 个转座子突变体文库，并在上行性尿路感染的小鼠模型中进行筛选。经过初步筛选和共感染实验确认后，鉴定出 19 个存活缺陷突变体。这些突变体在膀胱、肾脏或尿液中或在多个位点中回收的数量比野生型少 10(1) 至 10(6) 倍。对每个减毒突变体的转座子连接进行测序和分析。突变发现于：(i) 1 型菌毛操纵子； (ii)参与胞外多糖生物合成的基因，包括I组荚膜、II组荚膜和肠杆菌共同抗原； (iii) 参与代谢途径的基因； (iv) 功能未知的基因。所鉴定的基因中有 5 个在大肠杆菌 K-12 菌株的基因组中不存在。 1 型菌毛基因的突变导致定植严重减弱，即使在菌毛操纵子上游插入影响菌毛从“关闭”阶段到“开启”阶段转换速率的突变体也是如此。三个突变体在致病岛上的新型 II 型荚膜生物合成位点中插入，并且体内荚膜的产生受到损害。在 wecE 中插入的另一个突变体无法合成肠杆菌共同抗原。这些结果证实了 1 型菌毛的重要性，确立了细胞外多糖在 UTI 发病机制中的重要性，并确定了新的尿毒力决定因素。
Escherichia coli is the leading cause of urinary tract infections (UTIs). Despite the association of numerous bacterial factors with uropathogenic E. coli (UPEC), few such factors have been proved to be required for UTI in animal models. Previous investigations of urovirulence factors have relied on prior identification of phenotypic characteristics. We used signature-tagged mutagenesis (STM) in an unbiased effort to identify genes that are essential for UPEC survival within the murine urinary tract. A library of 2049 transposon mutants of the prototypic UPEC strain CFT073 was constructed using mini-Tn5km2 carrying 92 unique tags and screened in a murine model of ascending UTI. After initial screening followed by confirmation in co-infection experiments, 19 survival-defective mutants were identified. These mutants were recovered in numbers 10(1)- to 10(6)-fold less than the wild type in the bladder, kidneys or urine or at more than one site. The transposon junctions from each attenuated mutant were sequenced and analysed. Mutations were found in: (i) the type 1 fimbrial operon; (ii) genes involved in the biosyn-thesis of extracellular polysaccharides including group I capsule, group II capsule and enterobacterial common antigen; (iii) genes involved in metabolic pathways; and (iv) genes with unknown function. Five of the genes identified are absent from the genome of the E. coli K-12 strain. Mutations in type 1 fimbrial genes resulted in severely attenuated colonization, even in the case of a mutant with an insertion upstream of the fim operon that affected the rate of fimbrial switching from the 'off' to the 'on' phase. Three mutants had insertions in a new type II capsule biosynthesis locus on a pathogenicity island and were impaired in the production of capsule in vivo. An additional mutant with an insertion in wecE was unable to synthesize enterobacterial common antigen. These results confirm the pre-eminence of type 1 fimbriae, establish the importance of extracellular polysaccharides in the pathogenesis of UTI and identify new urovirulence determinants.