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.

Super-shed (SS)大肠杆菌O157 ( E.coli O157) 在牛直肠-肛门连接处鳞状上皮 (RSE) 细胞上表现出强的、聚集的、肠细胞消失 (LEE) 独立的粘附表型，并且在非肠道细胞中具有多态性-LEE 粘附相关基因座，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，我们评估了四种大肠杆菌O157 菌株 SS17、SS52、SS77 和 SS77 中的整个 Fim 操纵子（FimB-H）及其粘附（FimH）缺失突变体。EDL933，并在牛 RSE 和人 HEp-2 粘附测定中评估了粘附表型。与在大肠杆菌中基因关闭fimH表达的流行教条一致O157、ΔfimH SS52、ΔfimB-H SS52、ΔfimB-H SS17 和ΔfimH SS77 突变体对 RSE 细胞的粘附表型保持不变。相比之下，ΔfimH SS17 和ΔfimB-H SS77 突变体从野生型强和聚集转变为中度和弥漫性粘附表型，而ΔfimH EDL933 和ΔfimB-H EDL933 突变体均表现出与 RSE 细胞的增强结合（p < 0.05 ）。此外，ΔfimH SS17 和ΔfimH EDL933均不粘附于 HEp-2 细胞（p< 0.05)。突变株与它们各自的野生型基因的互补恢复了亲本表型。显微镜检查显示，SS17 和 EDL933 菌株确实带有比在尿路致病性大肠杆菌中看到的更短的 1 型菌毛样结构。总之，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。