The Occurrence of Ambient Temperature-Regulated Adhesins, Curli, and the Temperature-Sensitive Hemagglutinin Tsh among Avian Escherichia coli

Abstract

Escherichia coli establishes a secondary respiratory tract infection in birds following inhalation of contaminated dust and litter particles. Escherichia coli express adhesins under conditions reflective of the ambient temperatures present in poultry houses. These microbial adhesins allow E. coli to attach to cell types that it initially encounters in the respiratory tract. Ambient temperature-regulated adhesins represent a new class of bacterial hemagglutinins that include pili and the thin, aggregative, flexible filaments known as "curli." This study examines the occurrence of the ambient temperature-regulated adhesins, curli (crl, csgA), and an avian-specific, temperature-sensitive hemagglutinin, tsh, among avian and mammalian E. coli isolates. The avian hemagglutinin gene tsh was present in approximately 46% of clinical avian E. coli isolates. This gene was not detected among commensal E. coli isolated from healthy broiler chickens. Unlike tsh, curli genes were ubiquitous among E. coli. However, curli were observed in only half of the avian E. coli examined by electron microscopy. Curli were not present among several nonavian E. coli positive for crl and csgA. Approximately 25% of avian E. coli isolates agglutinated chicken erythrocytes when bacteria were grown at room temperature. Hemagglutination was not specific to E. coli isolated from poultry. Presence of either tsh or curli genes was not indicative of an isolate's ability to agglutinate chicken red blood cells. No discernible structures were observed mediating attachment of the bacteria to chicken red blood cells. An additional avian-specific hemagglutinin appears to be present among avian E. coli.

Genes of Virulence and Phylogenetic Group in Isolates of Avian Pathogenic Escherichia coli

“…fimH was detected with a frequency of 73%, coinciding with the 76.6% observed by Ghanbarpour et al [15]. The frequency of the fimbria curli was 73%, while Maurer et al [16] found it in all of the strains studied and Knobl et al [17] reported a frequency of 26%. Tsh has shown adhesion capacity to Caco-2 cells [18] and a prevalence between 10% to 90% was been reported for this gene [2,17,19,20].…”

Immunization with the binding domain of FimH, the adhesin of type 1 fimbriae, does not protect chickens against avian pathogenicEscherichia coli

“…A number of putative virulence factors have been discovered in APEC, including iron sequestering systems (aerobactin) (Dho & Lafont, 1984), the temperaturesensitive hemagglutinatin (TSH) (Maurer et al , 1998), resistance to serum (Dozois et al , 1992;Wooley et al , 1992) and fimbriae. Fimbriae (pili) are proteinaceous structures on the outer membrane of E. coli that mediate adherence of the bacteria to host epithelial cells, allowing them to overcome resident defence mechanisms of the respiratory tract and more successfully colonize.…”

Curli Fibers Are Required for Development of Biofilm Architecture in Escherichia coli K‐12 and Enhance Bacterial Adherence to Human Uroepithelial Cells

“…(34,35). Curli biogenesis is subject to tight and complex regulation; in E. coli, they are only produced at temperatures below 30 C, at low osmolarity, and in stationary phase (16,20,26). The biological function of curli remains to be solved.…”