E. coli 0157:H7 and hypertension, renal and cardiac disease

Text-size doesn't correlate with population size
Another not exactly HAI prevention post, but as Mike just told us, we don't have much evidence in ID, so anything can be exciting, no?  This report out of BMJ tells of a May 2000 E. coli O157:H7 and Campylobacter outbreak that arose in the Walkerton, Ontario municipal water system after heavy rainfall drove livestock faecal matter into water supply. The outbreak resulted in 2300 cases of GI illness, at least 27 cases of haemolytic-uraemic syndrome, and seven deaths.  Amazingly, the government created a Walkerton Health Study to monitor individuals for the possible long-term consequences associated with the infection.  After 4-years, there was a 28% increase in hypertension associated with the exposure.  The BMJ report tells of the impact out to 2008.

Overall, people who had acute gastroenteritis were 1.3 times more likely to develop hypertension, 3.4 times more likely to develop both structural and functional renal impairment, and 2.1 times more likely to report a physician-diagnosed cardiac disease. The authors do an excellent job discussing the potential limitations of the study including recall bias and confounding. They also explain away the impact of Campylobacter coinfection by saying that the infectious dose of 0157:H7 is 10 bacteria, while it is 500 for Campylobacter, so people were unlikely to have avoided 0157:H7 exposure.

This is a very unique study.  Most studies that have assessed infections as risk factors for chronic diseases were case-control studies that identified patients with specific outcomes and looked back for certain risk factors.  You would imagine that recall bias would play a much larger role in remembering certain distant and unremarkable exposures like GI illness in a case-control study. With this cohort study, exposures and outcomes were well characterized and measured.  I wonder what this study's impact will be in ascertaining the causes of hypertension, renal and cardiac disease in the general population?  Their recommendation that patients who are post-exposure from E coli 0157:H7 should be carefully monitored for hypertension and renal disease seems prudent.

Clark WF et al. BMJ Nov. 17, 2010 (open access)


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