title: Heterogeneous distributions of Escherichia coli O157 within naturally infected bovine faecal pats.
abstract: Escherichia coli O157 is an important human pathogen for which cattle are considered a reservoir. This paper describes and models the variation in counts of E. coli O157 that exists within individual bovine faecal pats. The presence and concentration of E. coli O157 in faecal samples was determined using a combination of direct spiral plating followed by a more sensitive isolation procedure. The data were modelled using multilevel random effect models, in which the random effects were allowed to be correlated to allow for the fact that pooled and individual samples come from the same pat. Up to a two log difference in the concentration of E. coli O157 was demonstrated in samples from different areas within a faecal pat. Pooling of individual samples from throughout the faecal pat and processing it as one composite sample allows this heterogeneity to be overcome.
authors.affiliation: DEFRA Epidemiology Fellowship Unit, University of Liverpool, Leahurst, Neston, South Wirral, UK. s.e.robinson@liv.ac.uk
authors.forename: Susan E
authors.initials: SE
authors.lastname: Robinson
authors.forename: Patrick E
authors.initials: PE
authors.lastname: Brown
authors.forename: E
authors.initials: E
authors.lastname: John Wright
authors.forename: Malcolm
authors.initials: M
authors.lastname: Bennett
authors.forename: C Anthony
authors.initials: CA
authors.lastname: Hart
authors.forename: Nigel P
authors.initials: NP
authors.lastname: French
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D002417:Cattle / Q000382:microbiology*; D015169:Colony Count, Microbial / Q000379:methods / Q000706:statistics & numerical data; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology*