Risk of Infection from Exposure to Waterborne Helicobacter pylori?

Abstract

Helicobacter pylori is a stomach bacterium that, while asymptomatic in most people, can cause a cascade of pathology leading to gastric cancer. When outside the human stomach, H. pylori undergoes a morphological change, transitioning into a viable but nonculturable (VBNC) state. This transition has made it challenging to characterize transmission and the infection risk associated with different routes of H. pylori exposure.

In 1991 in Lima, Peru, researchers first associated H. pylori infection with water source. Since then, H. pylori has been associated with lack of access to clean drinking water and sanitation, and the bacterium has been identified in drinking water sources. Working together with Peruvian stakeholders and scientists at the University of Michigan, this dissertation aims to provide information that will help better characterize the risk posed by waterborne H. pylori. Thus, the overarching hypothesis of my dissertation is that water can act as a reservoir for H. pylori. In Chapter 1, we conducted an exposure assessment, quantifying the extent of drinking water contamination with H. pylori in Lima and found consistent contamination with H. pylori, without any seasonal patterns. In Chapter 2, we developed a mouse model to examine the infectiousness of H. pylori in drinking water. We found that higher doses of culturable H. pylori strain SS1 in drinking water cause higher incidence of infection, but that mice exposed to the VBNC form of SS1 were not infected, regardless of dose. In Chapter 3, we examined strategies to control H. pylori infection in Lima. First, we investigated H. pylori antibiotic resistance the success rate of antibiotic therapy. We found high rates of antibiotic resistance, and a lower than-expected success rate of antibiotic therapy at 6-8 weeks. Second, we tested the H. pylori reduction capacities of bleach disinfection and boiling water, and found that both treatments resulted in total loss of culturability.

This research highlights the importance of examining the infectivity of different strains of H. pylori, as well as characterizing the factors that lead contribute to H. pylori survival and infectivity in drinking water. Many thanks to my colleagues for their important contributions to this work.