Associations between the presence of virulence determinants and the epidemiology and ecology of zoonotic escherichia coli

O'Reilly, K.M., Low, J.C., Denwood, M.J., Gally, D.L., Evans, J., Gunn, G.J., Mellor, D.J., Reid, S.W.J. and Matthews, L. (2010) Associations between the presence of virulence determinants and the epidemiology and ecology of zoonotic escherichia coli. Applied and Environmental Microbiology, 76(24), pp. 8110-8116. (doi:10.1128/AEM.01343-10)

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Abstract

The severity of human infection with pathogenic Escherichia coli depends on two major virulence determinants (eae and stx) that, respectively, produce intimin and Shiga toxin. In cattle, both may enhance colonization, but whether this increases fitness by enhancing cattle-to-cattle transmission in the field is unknown. In E. coli O157, the almost uniform presence of the virulence determinants in cattle isolates prevents comparative analysis. The availability to this study of extensive non-O157 E. coli data, with much greater diversity in carriage of virulence determinants, provides the opportunity to gain insight into their potential impact on transmission. Dynamic models were used to simulate expected prevalence distributions for serogroups O26 and O103. Transmission parameters were estimated by fitting model outputs to prevalence data from Scottish cattle using a Bayesian Markov chain Monte Carlo (MCMC) approach. Despite similar prevalence distributions for O26 and O103, their transmission dynamics were distinct. Serogroup O26 strains appear well adapted to the cattle host. The dynamics are characterized by a basic reproduction ratio (R-0) of >1 (allowing sustained cattle-to-cattle transmission), a relatively low transmission rate from environmental reservoirs, and substantial association with eae on transmission. The presence of stx(2) was associated with reduced transmission. In contrast, serogroup O103 appears better adapted to the noncattle environment, characterized by an R-0 value of <1 for plausible test sensitivities, a significantly higher transmission rate from noncattle sources than serogroup O26, and an absence of fitness benefits associated with the carriage of eae. Thus, the association of eae with enhanced transmission depends on the E. coli serogroup. Our results suggest that the capacity of E. coli strains to derive fitness benefits from virulence determinants influences the prevalence in the cattle population and the ecology and epidemiology of the host organism.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Mellor, Professor Dominic and Denwood, Dr Matthew and O'Reilly, Dr Kathleen and Matthews, Professor Louise and Reid, Professor Stuart
Authors: O'Reilly, K.M., Low, J.C., Denwood, M.J., Gally, D.L., Evans, J., Gunn, G.J., Mellor, D.J., Reid, S.W.J., and Matthews, L.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
College of Medical Veterinary and Life Sciences > School of Veterinary Medicine
Journal Name:Applied and Environmental Microbiology
ISSN:0099-2240
ISSN (Online):1098-5336
Published Online:15 October 2010

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