Diversity of Escherichia coli from the enteric microbiota in patients with Escherichia coli bacteraemia

Abstract

ObjectiveThe increase in Escherichia coli bloodstream infections mandates better characterisation of the relationship between commensal and invasive isolates. This study established a simple approach to characterize diversity of E. coli in the gut reservoir from patients with either E. coli bacteraemia, other Gram-negative bacteraemia, or patients without bacteraemia not receiving antibiotics. Stool or rectal swabs from patients in the three groups were cultured on selective chromogenic agar. Genetic diversity of E. coli in gut microbiota was estimated by RAPD-PCR. ResultsEnteric samples from E. coli bacteraemia patients yielded a median of one E. coli RAPD pattern (range 1-4) compared with two (range 1-5) from groups without E. coli bacteraemia. Of relevance to large-scale clinical studies, observed diversity of E. coli among E. coli bacteraemia patients was not significantly altered by sample type (rectal swab or stool), nor by increasing the colonies tested beyond ten. Overall, hospitalised patients demonstrated an apparently limited diversity of E. coli in the enteric microbiota and this was further reduced in those with E. coli bacteraemia. The reduced diversity of E. coli within the gut during E. coli bacteraemia raises the possibility that dominant strains may outcompete other lineages in patients with bloodstream infection.