Characterization of the second long polar (LP) fimbriae of O157:H7 and distribution of LP fimbriae in other pathogenic strains

Abstract

A second region containing five genes homologous to the long polar fimbrial operon of Salmonella enterica serovar Typhimurium is located in the chromosome of enterohemorrhagic Escherichia coli (EHEC) O157:H7. A non-fimbriated E. coli K-12 strain carrying the cloned EHEC lpf (lpf2) genes expressed thin fibrillae-like structures on its surface and displayed reduced adherence to tissue culture cells. Neither mutation in the lpfA2 gene in either the parent or lpfA1 mutant strains showed an effect in adherence or in the formation of A/E lesions on HeLa cells. lpfA2 isogenic mutant strains adhere to Caco-2 cells almost as well as the wild-type at 5 h, but they were deficient in adherence at early time points. A collection of diarrheagenic E. coli strains were investigated for the presence of lpfA1 and lpfA2 and results showed that these genes are present in specific serogroups which are phylogenetically related. Our results suggest that LP fimbriae 2 may contribute to the early stages of EHEC adhesion and that genes encoding the major LP fimbrial subunits are present in a small group of EHEC and EPEC serotypes.

Differential Binding of Escherichia coli O157:H7 to Alfalfa, Human Epithelial Cells, and Plastic Is Mediated by a Variety of Surface Structures

“…These mutations also cause E. coli O157:H7 to display increased virulence in mice and increased invasion of HEp-2 cells (48). We previously reported that E. coli O157:H7 is not an invasive organism and that a mutation in the csgD gene does not increase the invasion ability of the mutant compared to the E. coli O157:H7 wild-type strain (43). Although it has been reported that curli production by E. coli O157:H7 enhances biofilm formation on inert surfaces, i.e., stainless steel (37,38), our data do not support these findings.…”

“…Caco-2 cells were seeded with 1 ϫ 10 5 cells/well and incubated for 48 h at 37°C with 5% CO 2 in 24-well plates (Corning, Inc., Corning, NY). The cell monolayers were washed twice with phosphatebuffered saline (pH 7.4), and the infection was carried out with wild-type bacteria and isogenic mutants as described previously (43). Briefly, bacterial strains were grown in LB broth overnight at 37°C, the monolayers were infected with 1 ϫ 10 7 bacteria for 3 h, and adherence was evaluated qualitatively by Giemsa staining and quantitatively by plating adherent bacteria on L agar plates with an appropriate antibiotic.…”

Evolution of the Chaperone/Usher Assembly Pathway: Fimbrial Classification Goes Greek

“…Uropathogenic P. mirabilis isolates also contain a member of the ␥ 1 -fimbrial clade, the ambient-temperature fimbria (atf) operon; however, the encoded adhesin is not required for cystitis in a mouse model (213,214,373). Gene clusters that are closely related to the ␥ 1 -fimbriae include the lpf operons of S. enterica (28), enterohemorrhagic E. coli (77,334,335), enteropathogenic E. coli (232), and extraintestinal pathogenic E. coli (146). In S. enterica serotype Typhimurium, the lpf operon has been implicated in intestinal colonization in a mouse model (29,351).…”

Pathogenesis of Human Enterovirulent Bacteria: Lessons from Cultured, Fully Differentiated Human Colon Cancer Cell Lines

“…The role of LEE gene transcription in the adhesion of EHEC has been analyzed using fully differentiated Caco-2 cells (493)(494)(495)(496). OmpA and the long polar fimbriae of EHEC are two other factors that allow EHEC to adhere to the brush border of fully differentiated Caco-2 cells (497,498). EHEC encodes adherence-associated loci that are involved in the initial diffuse adherence, and the intimin-Tir interaction is required for the subsequent development of EHEC microcolonies at the brush border of fully differentiated Caco-2 cells (496).…”