THE OCCURRENCE OF AMBIENT TEMPERATURE-REGULATED ADHESINS, CURLI, AND THE TEMPERATURE-SENSITIVE HEMAGGLUTININ TSH AMONG AVIAN ESCHERICHIA-COLI

Escherichia coli establishes a secondary respiratory tract infection i n birds following inhalation of contaminated dust and litter particles . Escherichia call express adhesins under conditions reflective of the ambient temperatures present in poultry houses. These microbial adhes ins allow E. coli to attach to cell types that it initially encounters in the respiratory tract. Ambient temperature-regulated adhesins repr esent a new class of bacterial hemagglutinins that include pill and th e 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 hema gglutinin, tsh, among avian and mammalian E. roll isolates. The avian hemagglutinin gene trh was present in similar to 46% of clinical avian E. roll isolates. This gene was not detected among commensal E. coli isolated from healthy broiler chickens. Unlike tsh, curli genes were u biquitous among E. coli. However, curli were observed in only half of the avian E. coli examined by electron microscopy. Curli were not pres ent among several nonavian E. coli positive for crl and csgA. Approxim ately 25% of avian E. coli isolates agglutinated chicken erythrocytes when bacteria were grown at room temperature. Hemagglutination was not specific to E. roll 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 media ting attachment of the bacteria to chicken red blood cells. An additio nal avian-specific hemagglutinin appears to be present among avian E: roll.