Genotypic diversity of Escherichia coli isolated from cecal content and mucosa of one- to six-week-old broilers

Abstract

Escherichia coli is a component of the microbiota of the avian digestive tract and is also part of some of the defined cultures used for competitive exclusion of Salmonella. Of particular interest are E. coli that are able to associate with the cecal wall because they might be part of a barrier that block pathogens from attaching and possibly from gaining entrance to intestinal tissues. In this study, repetitive element (rep)-PCR using the BOXA1R primer was used to differentiate between E. coli isolates obtained from cecal content and mucus of 1- to 6-wk-old broiler chickens. Computer-assisted analysis of the fingerprint patterns obtained from the isolates indicated the presence of 2 major groups of patterns. Collectively these 2 groups consisted of 28 clusters of patterns that differed from each other by 30% or more (dissimilarity index of > or = 0.3) and were therefore designated as operational taxonomic units. The patterns obtained from isolates from birds aged 1 to 5 wk were distributed almost equally between the 2 major groups, but approximately 90% of the patterns from isolates obtained from 6-wk-old birds belonged to only 1 of the 2 groups. The diversity of the fingerprints indicates that cecal mucus is inhabited by several types of E. coli in individual birds and in the birds housed together. Evidence for the preferential localization of specific E. coli within the cecal mucosa was not found, and therefore a range of E. coli must be able to associate tightly with the cecal mucosa.