MedWire News: Infection with enteric Salmonella or Campylobacter is unlikely to increase the risk for inflammatory bowel disease (IBD), say researchers who suggest that any observed association is due to detection bias as a result of increased stool testing of these patients.

As reported in the journal Gut, Morten Frisch (Statens Serum Institut, Copenhagen, Denmark) and colleagues evaluated claims that enteric pathogens such as Salmonella or Campylobacter could be implicated in the development of IBD.

Frisch and team followed up the Danish population (a national cohort of 6.9 million people) for 94.3 million person-years between 1992 and 2008. They used national registers to identify people with positive and negative stool tests for Salmonella or Campylobacter and those with IBD.

Incidence rate ratios (IRRs) for IBD ranged from 5.4-9.8 in the first year after a positive stool test for either pathogen and remained moderately increased compared with the general population in the 1-10 year period after testing, with IRRs ranging from 1.6-2.2.

However, IRRs for IBD in the first year after a negative stool test for Salmonella or Campylobacter were even higher, at 53.2-57.5, and had a similar decreasing incidence pattern over the following 10 years to those with positive stool test results.

These results confirm previous findings showing "an increased risk of IBD following enteric infections with Salmonella or Campylobacter, but also reveals that the risk pattern is strikingly parallel and even more pronounced following stool examinations with a negative outcome," say the authors.

"With due reservations, our findings strongly suggest that the risk previously ascribed to acute bacterial gastroenteritis reflects detection bias related to increased stool testing rather than causality," they conclude.

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