The role of intimin and flagella in the persistence of Escherichia coli O157:H7 in poultry

Best, Angus (2003) The role of intimin and flagella in the persistence of Escherichia coli O157:H7 in poultry. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Escherichia coli O157:H7 has been implicated in many major and sporadic outbreaks of food-borne related disease in humans. Bovine and bovine derived meat products are cited as the main source of infection and deliberate inoculation studies of ruminants show that the surface-arrayed outer membrane protein intimin facilitates persistent colonisation. The prevalence of E. coli O157:H7 infection in birds is low, but several deliberate inoculation studies show that poultry are readily and persistently infected by this organism indicating a possible threat to public health. The mechanisms of E. coli O157:H7 colonisation of poultry are not understood, but flagella are important for the colonisation of poultry by avian pathogenic E. coli. Whether intimin plays a role in persistent colonisation of poultry has not been determined. To investigate the role of intimin and flagella, defined knockout single and double intimin and aflagellate mutants were constructed in a well characterised non-toxigenic E. coli O157:H7 isolate (NCTC 12900) and tested in adherence assays with an avian epithelial cell line (Div-1) and used to inoculate 1-day-old SPF chicks. In vitro, NCTC 12900 intimin contributed significantly to adherence, but not invasion, whereas NCTC 12900 flagella only contributed to invasion. NCTC 12900 intimin, but not flagella was required for micro-colony and AE lesion formation. In vivo studies revealed that the wild-type could form micro-colonies on the caecal mucosa of SPF chicks and could persistently colonise birds for up to 169 days, ceasing 9 days after the birds came into lay and 6% of eggs were contaminated on the eggshell. NCTC 12900 flagella, but not intimin contributed to persistent colonisation in the chick.