Evaluating the Potential for a Helicobacter pylori Drinking Water Guideline

Abstract

Helicobacter pylori is a microaerophilic, gram-negative bacterium that is linked to adverse health effects including ulcers and gastrointestinal cancers. The goal of this analysis is to develop the necessary inputs for a quantitative microbial risk assessment (QMRA) needed to develop a potential guideline for drinking water at the point of ingestion (e.g., a maximum contaminant level, or MCL) that would be protective of human health to an acceptable level of risk while considering sources of uncertainty. Using infection and gastric cancer as two discrete endpoints, and calculating dose-response relationships from experimental data on humans and monkeys, we perform both a forward and reverse risk assessment to determine the risk from current reported surface water concentrations of H. pylori and an acceptable concentration of H. pylori at the point of ingestion. This approach represents a synthesis of available information on human exposure to H. pylori via drinking water. A lifetime risk of cancer model suggests that a MCL be set at <1 organism/L given a 5-log removal treatment because we cannot exclude the possibility that current levels of H. pylori in environmental source waters pose a potential public health risk. Research gaps include pathogen occurrence in source and finished water, treatment removal rates, and determination of H. pylori risks from other water sources such as groundwater and recreational water.

A generalized dose-response relationship for adenovirus infection and illness by exposure pathway

“…Second, the hierarchical framework allows sharing information among studies: by assuming that inoculation route affects only the mean values of the location parameters for infection ( w ) and illness ( ) we have implied that the remaining parameters are independent of inoculation route, and may be estimated from all observations jointly. Both the oral and ocular droplet inoculation data do not show trend [31]: they only provide information that the applied doses are sufficient for causing 100% infection. Doses of the same magnitude also suffice to cause infection in all exposed via the other inoculation pathways, so that exclusion of the oral and ocular droplet inoculation data would have little effect on the remaining dose-response relationships.…”

Environmental (Saprozoic) Pathogens of Engineered Water Systems: Understanding Their Ecology for Risk Assessment and Management

“…Nonetheless, estimates of L. pneumophila densities to cause Legionnaires’ Disease from drinking waters are likely to be very high (some millions of cells per liter) [ 16 ], with epidemiologic data indicating lesser numbers related to Pontiac Fever (thousands of cells per liter) [ 93 ]. Hence, the general expectation is that several orders of magnitude higher doses are probably required for saprozoic pathogens compared to enteric pathogens via drinking water [ 110 ]; with the possible exception of Naegleria fowleri [ 30 ] and Helicobacter pylori (<1 cell per liter) [ 111 ] that may accumulate (unclear if any growth) in drinking water biofilms [ 112 ].…”

Animal Model Reveals Potential Waterborne Transmission of Helicobacter pylori Infection

“…Our results show that H. pylori in water is infectious and thus may be a risk to human health. A recent quantitative microbial risk assessment (QMRA) of H. pylori in water agreed, suggesting a maximum contaminant level at one organism per liter .…”