A new study by researchers at the University of California, Berkely has revealed that household environments play a larger role in bacterial transmission than previously understood. Their research shows that stored drinking water serves as a key transmission pathway for E. coli bacteria within and between households in developing countries.
The majority of E. coli strains are not harmful and play a crucial role in maintaining a healthy gut ecosystem by assisting in breaking down the food, contributing to the production of essential vitamins, and acting as a defense mechanism against more dangerous microorganisms.
However, not all E. coli are benign. Certain strains can cause a range of health issues in humans, including gastrointestinal distress resulting in diarrhea, infections of the urinary tract, respiratory ailments like pneumonia, and even severe systemic infections such as sepsis. Symptoms generally appear two to five days after exposure but can emerge anywhere from one to eight days later. Most people recover within 5-10 days.
Of particular concern, however, is the potential for some patients to develop Hemolytic Uremic Syndrome (HUS), a severe complication that can lead to kidney failure, neurological damage, and in extreme cases, death. This risk makes early medical intervention crucial for infected individuals.
The study provides new insights into how contaminated drinking water contributes to the spread of gastrointestinal infections and antibiotic-resistant bacterial strains. These findings could lead to effective strategies for protecting children’s health in vulnerable communities.
The research team, led by Amy Pickering, associate professor of civil and environmental engineering, shifted focus from the commonly studied bacteria exchange between animals and humans to investigate the less-examined pathways of drinking water and soil. Their findings ultimately demonstrated that water represents one of the most significant transmission routes for pathogenic and drug-resistant bacteria.
To track bacterial spread across different pathways, Pickering’s team developed a scalable method called PIC-seq (Pooled Isolated Colonies-seq). This technique enhanced their research capabilities by allowing them to sequence multiple bacterial strains per sample instead of just one, providing more comprehensive views of strain sharing patterns within and between households.
The study focused on households in informal urban settlements in Nairobi, Kenya, where drinking water is typically stored in jerry cans and plastic buckets. By collecting and analyzing samples from human stool, animal feces, stored water, and soil, the researchers discovered that bacterial strain-sharing occurred more frequently between humans and stored drinking water than between humans and domesticated animals within the same household.
Postdoctoral researcher Daniel Daehyun Kim, the study’s lead author, noted that these results emphasize the environment’s substantial role in bacterial transmission, potentially exceeding that of animals.
The researchers also identified E. coli strains carrying high-risk antibiotic resistance genes in the contaminated water samples. These genes can potentially transfer to other bacteria, facilitating the spread of antibiotic-resistant strains throughout communities.
Importantly, the study found that households with access to chlorinated water had lower rates of E. coli contamination in their stored drinking water. This suggests that community-level water chlorination could effectively prevent bacterial spread between household members and across different households.
