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Campylobacter jejuni reveals genetic markers predictive of infection source

November 1, 2005
Proceedings of the National Academy of Sciences (PNAS) Volume 102, Number 44, 16043-16048
Olivia L. Champion *, Michael W. Gaunt *, Ozan Gundogdu *, Abdi Elmi *, Adam A. Witney {dagger}, Jason Hinds {dagger}, Nick Dorr
Published: 01.nov.05
*Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom; and {dagger}Bacterial Microarray Group, Medical Microbiology, Department of Cellular and Molecular Medicine, St. George’s, University of London, Cranmer Terrace, London SW17 0RE, United Kingdom
Edited by Stanley Falkow, Stanford University, Stanford, CA and approved September 12, 2005 (received for review May 12, 2005)
Campylobacter jejuni is the predominant cause of bacterial gastroenteritis worldwide, but traditional typing methods are unable to discriminate strains from different sources that cause disease in humans. We report the use of genomotyping (whole-genome comparisons of microbes using DNA microarrays) combined with Bayesian-based algorithms to model the phylogeny of this major food-borne pathogen. In this study 111 C. jejuni strains were examined by genomotyping isolates from humans with a spectrum of C. jejuni-associated disease (70 strains), chickens (17 strains), bovines (13 strains), ovines (5 strains), and the environment (6 strains). From these data, the Bayesian phylogeny of the isolates revealed two distinct clades unequivocally supported by Bayesian probabilities (P = 1); a livestock clade comprising 31/35 (88.6%) of the livestock isolates and a “nonlivestock” clade comprising further clades of environmental isolates. Several genes were identified as characteristic of strains in the livestock clade. The most prominent was a cluster of six genes (cj1321 to cj1326) within the flagellin glycosylation locus, which were confirmed by PCR analysis as genetic markers in six additional chicken-associated strains. Surprisingly these studies show that the majority (39/70, 55.7%) of C. jejuni human isolates were found in the nonlivestock clade, suggesting that most C. jejuni infections may be from nonlivestock (and possibly nonagricultural) sources. This study has provided insight into a previously unidentified reservoir of C. jejuni infection that may have implications in disease-control strategies. The comparative phylogenomics approach described provides a robust methodological prototype that should be applicable to other microbes.