An analysis of children affected by a Salmonella enteritidis outbreak more than 20 years ago provides evidence that pathogen-induced gastroenteritis during childhood is a risk factor for irritable bowel syndrome (IBS) in adults. The findings from this long-term study are published in the July issue of Gastroenterology.
Functional dyspepsia and IBS affect 20%–30% of the population. Acute infectious gastroenteritis (infections caused by Salmonella, Shighella, Campylobacter, or Norovirus) is the strongest known risk factor for the development of IBS, accounting for 6%–17% of all cases.
However, there is limited information on the long-term outcomes of children with infectious gastroenteritis—are they more likely to have IBS or functional dyspepsia as adults? Functional gastrointestinal disorders during adulthood might be caused by early life experiences, when the gastrointestinal tract is developing.
Cesare Cremon et al. identified and monitored individuals affected by a foodborne Salmonella enteritidis outbreak that involved 1811 people in Bologna, Italy in 1994. The outbreak resulted from delivery of contaminated tuna sauce to 36 schools. Although some adult staff became ill, 93% of those affected were children, 3–10 years old.
Sixteen years later, Cremon et al. evaluated the long-term effects of the outbreak, mailing a questionnaire to 757 subjects. They analyzed data collected from 250 randomly selected adults who had been exposed to Salmonella as children, all 127 individuals who were exposed as adults, and matched non-exposed participants (controls).
Among exposed participants, 32.3% reported functional dyspepsia, compared with 27.1% of controls, and 36.8% reported having IBS, compared with 23.3% of controls. The odds ratio for IBS among people exposed to the Salmonella was 1.92.
Interestingly, a greater proportion of individuals exposed to Salmonella as children developed IBS (35.3%) than controls (20.5%), but not a greater proportion of individuals exposed to the pathogen as adults. Cremon et al. did not find evidence that antibiotic treatment contributed to post-infection symptoms.
In an editorial that accompanies the article, John K. Marshall explains that this is the youngest cohort in which the gastrointestinal sequelae of acute infection have been studied prospectively.
Marshall says that because little is known about additional infections, antibiotic use, and environmental exposures in the 16-year interval between the outbreak and the final study assessment, it might be too simplistic to think that a single infectious event would determine a lifelong risk of functional disorders.
He proposes that future studies track interval infections and other environmental exposures with more granularity, such that risk estimates reflect not binary relationships but more complex integrations of lifetime food, infection, and other environmental exposures (see above figure).
Nonetheless, Cremon et al. conclude that given the high prevalence of acute gastroenteritis and Salmonellosis among children, preventive measures are needed to reduce their risk for IBS as adults.