Access to clean drinking water is pivotal to human health yet is still a limited resource for a large proportion of the world’s population.

Bacterial pathogens threaten lives with new pathogenic strains and those resistant to antibiotics consistently emerging over time. This study investigates how consumption of polluted waters affects the gut microbiome.

Enteric bacterial pathogens in polluted drinking water sources in coastal Bangladesh are being characterised and quantified over a six-month period. During the same timeframe, the gut bacteria of individuals consuming polluted drinking water are being analysed and compared to samples from their water sources.

The objectives of this project include:

1. Demonstrating the acquisition of enteric pathogens in the gut microbiome of individuals consuming polluted water.
2. Determining the effects on the gut microbiome when a cleaner drinking water source is provided.
3. Conducting a qualitative analysis of health and social outcomes resulting from the provision of clean water.

It is hypothesised that a major enteric pathogen, V. cholerae, evolved in the Ganges Delta, an environment with low level rivers that are regularly inundated with marine waters. Therefore, human consumption of inundated water provides ample opportunity for diverse V. cholerae strains to pass through the human gut and for pathogenic strains to be selected for and amplified in number. However, little is known about the diversity of V. cholerae (or other Vibrio species) transiting the gut of people that regularly consume polluted waters and how these relate to strains causing deadly outbreaks. The same is true of other waterborne bacterial enteric pathogens that are common in Bangladesh, such as E. coli, Shigella and Salmonella.

Mathbaria, located in the Barisal district of Bangladesh, is identified as an area especially susceptible to the consumption of water contaminated by enteric pathogens. This location contains around 50,000 households with a total population of ~250,000. It is located in a coastal area which suffers from salinity intrusion and high arsenic levels in groundwater, making water from wells undrinkable. People rely on alternative sources of water, harvesting rain in shallow ponds. These ponds are frequently contaminated with faecal coliforms, and to make the collected water drinkable, pond sand filters are used to purify it. These filters do not always adequately purify the water and the overall satisfaction with their use is mixed, given the added waiting time and walking distance to get water. Some households can afford to install their own rainwater harvesting systems, generally providing much cleaner water that is easily accessible, a source for drinking water with a much higher satisfaction rating from users.

Although the safety of these drinking water sources has been tested both in terms of microbial contamination (usually by simple faecal coliform counts) and chemical safety (testing salinity and arsenic levels), these do not inform on the risk of pathogens transiting in the gut microbiomes. It also remains that there are no comprehensive studies linking water source to changes in the human gut microbiome. This study is unique in that it uses a One Health perspective to explore the circulation of pathogens between the human gut and the environment, providing detailed insight into the role of both as reservoirs and incubators for the evolution of novel pathogenic strains.