The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA.
Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA, USA.
Int J Med Microbiol. 2021 May;311(4):151511. doi: 10.1016/j.ijmm.2021.151511. Epub 2021 May 5.
Super-shed (SS) Escherichia coli O157 (E. coli O157) demonstrate a strong, aggregative, locus of enterocyte effacement (LEE)-independent adherence phenotype on bovine recto-anal junction squamous epithelial (RSE) cells, and harbor polymorphisms in non-LEE-adherence-related loci, including in the type 1 fimbriae operon. To elucidate the role of type 1 fimbriae in strain- and host-specific adherence, we evaluated the entire Fim operon (FimB-H) and its adhesion (FimH) deletion mutants in four E. coli O157 strains, SS17, SS52, SS77 and EDL933, and evaluated the adherence phenotype in bovine RSE and human HEp-2 adherence assays. Consistent with the prevailing dogma that fimH expression is genetically switched off in E. coli O157, the ΔfimHSS52, ΔfimB-HSS52, ΔfimB-HSS17, and ΔfimHSS77 mutants remained unchanged in adherence phenotype to RSE cells. In contrast, the ΔfimHSS17 and ΔfimB-HSS77 mutants changed from a wild-type strong and aggregative, to a moderate and diffuse adherence phenotype, while both ΔfimHEDL933 and ΔfimB-HEDL933 mutants demonstrated enhanced binding to RSE cells (p < 0.05). Additionally, both ΔfimHSS17 and ΔfimHEDL933 were non-adherent to HEp-2 cells (p < 0.05). Complementation of the mutant strains with their respective wild-type genes restored parental phenotypes. Microscopy revealed that the SS17 and EDL933 strains indeed carry type 1 fimbriae-like structures shorter than those seen in uropathogenic E. coli. Taken together, these results provide compelling evidence for a strain and host cell type-dependent role of fimH and the fim operon in E. coli O157 adherence that needs to be further evaluated.
超级脱落（SS）大肠杆菌 O157（大肠杆菌 O157）在牛直肠肛门交界处鳞状上皮（RSE）细胞上表现出强烈的、聚集的、肠上皮细胞消失（LEE）非依赖性粘附表型，并且在非 LEE 粘附相关基因座中存在多态性，包括在 1 型菌毛操纵子中。为了阐明 1 型菌毛在菌株和宿主特异性粘附中的作用，我们评估了四个大肠杆菌 O157 菌株 SS17、SS52、SS77 和 EDL933 的整个 Fim 操纵子（FimB-H）及其粘附（FimH）缺失突变体，并在牛 RSE 和人 HEp-2 粘附测定中评估了粘附表型。与普遍的教条一致，即 fimH 表达在大肠杆菌 O157 中被遗传关闭，ΔfimHSS52、ΔfimB-HSS52、ΔfimB-HSS17 和 ΔfimHSS77 突变体在 RSE 细胞上的粘附表型保持不变。相比之下，ΔfimHSS17 和 ΔfimB-HSS77 突变体从野生型强而聚集的粘附表型转变为中度而弥散的粘附表型，而 ΔfimHEDL933 和 ΔfimB-HEDL933 突变体均显示出对 RSE 细胞的结合增强（p<0.05）。此外，ΔfimHSS17 和 ΔfimHEDL933 都不能粘附到 HEp-2 细胞上（p<0.05）。用相应的野生型基因互补突变株恢复了亲本表型。显微镜观察显示，SS17 和 EDL933 菌株确实携带比尿路致病性大肠杆菌短的 1 型菌毛样结构。综上所述，这些结果为 fimH 和 fim 操纵子在大肠杆菌 O157 粘附中的菌株和宿主细胞类型依赖性作用提供了令人信服的证据，需要进一步评估。
