Elucidating the Aetiology of Human <i>Campylobacter coli</i> Infections

<div><p>There has been little research on the determinants of <i>Campylobacter coli</i> infection, despite its contributing up to 10% of human <i>Campylobacter</i> infections. A case-control and two case-case study methods explored the aetiology of <i>C. coli</i> over a one year period across Scotland. The case-control multivariate model found an increased risk of <i>C. coli</i> infection in people older than 19 years (O.R. = 3.352), and during the summer months (O.R. = 2.596), while residing in an urban area decreased the risk (O.R. = 0.546). The first case-case study compared <i>C. coli</i> and <i>C. jejuni</i> cases and also showed a higher risk of <i>C. coli</i> during the summer (O.R. = 1.313) and in people older than 19 years (O.R. = 0.791). Living in an urban area was associated with a reduced risk of infection (O.R. = 0.769). Multi-locus sequence typing (MLST) indicated that sheep and chicken <i>C. coli</i> sequence types (STs) were most frequently found in humans whilst those from cattle and pigs were rarer. MLST diversity was high in isolates from pigs and chicken, intermediate in human isolates, and low in ruminant isolates. The second case-case study used MLST data to ascribe putative sources of infection to the cases. The putative source for 40% of cases was chicken, with 60% acquired from other sources (ruminants 54% and pigs 6%). The case-case analysis also showed that female gender was a risk factor (O.R. = 1.940), which may be explained by females being more likely to prepare poultry in the home. These findings indicate differences between the aetiology of <i>C. coli</i> and <i>C. jejuni</i> infections: this should be taken into account by public health professionals when developing strategies to reduce the burden of human campylobacteriosis.</p>