Phylogenomic approaches to determine the zoonotic potential of Shiga toxin-producing Escherichia coli (STEC) isolated from Zambian dairy cattle

Geoffrey Mainda, Nadejda Lupolova, Linda Sikakwa, Paul R. Bessell, John B. Muma, Deborah V. Hoyle, Sean P. McAteer, Kirsty Gibbs, Nicola J. Williams, Samuel K. Sheppard, Roberto M. La Ragione, Guido Cordoni, Sally A. Argyle, Sam Wagner, Margo E. Chase-Topping, Tim Dallman, Mark P. Stevens, Barend M.Dec Bronsvoort, David L. Gally*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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This study assessed the prevalence and zoonotic potential of Shiga toxin-producing Escherichia coli (STEC) sampled from 104 dairy units in the central region of Zambia and compared these with isolates from patients presenting with diarrhoea in the same region. A subset of 297 E. coli strains were sequenced allowing in silico analyses of phylo-and sero-groups. The majority of the bovine strains clustered in the B1 'commensal' phylogroup (67%) and included a diverse array of serogroups. 11% (41/371) of the isolates from Zambian dairy cattle contained Shiga toxin genes (stx) while none (0/73) of the human isolates were positive. While the toxicity of a subset of these isolates was demonstrated, none of the randomly selected STEC belonged to key serogroups associated with human disease and none encoded a type 3 secretion system synonymous with typical enterohaemorrhagic strains. Positive selection for E. coli O157:H7 across the farms identified only one positive isolate again indicating this serotype is rare in these animals. In summary, while Stx-encoding E. coli strains are common in this dairy population, the majority of these strains are unlikely to cause disease in humans. However, the threat remains of the emergence of strains virulent to humans from this reservoir.

Original languageEnglish
Article number26589
JournalScientific Reports
Publication statusPublished - 25 May 2016

Bibliographical note

Funding Information:
We are grateful to the Government of the Republic of Zambia (GRZ) and the University of Zambia for facilitating the field and laboratory research while in Zambia. We are indepted to the help of Geoffrey Kwenda and Sydney Malama to enable collection of the human E. coli isolates. We acknowledge access to pathogenic avian strains supplied by Zoetis. G.M. is grateful to the Commonwealth Scholarship Commission (CSC) for providing funding (ZMSC-2012-640). N.L. acknowledges support from a University of Edinburgh College studentship. D.L.G., S.P.M., M.P.S. and B.M.B. receive core strategic funding to The Roslin Institute from the Biotechnology & Biological Sciences Research Council (BB/J004227/1). The sequencing by PHE was funded by the National Institute for Health Research scientific research development fund (108601).


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