When you think about probiotics, you might picture fancy yogurt, or perhaps the kombucha that you innocently tasted at the farmer’s market downtown. Now scientists are considering a probiotic approach to water plumbing systems in buildings, as a way to suppress growth of harmful microbes in our drinking water. A review of this emerging area of research was published by Dr. Amy Pruden and colleagues at Virginia Tech in Environmental Science and Technology.
A probiotic approach to plumbing would favor the growth of some microbes — harmless, and thus ‘probiotic’ ones — in our drinking water over microbes that could make you sick. And yes, our drinking water contains microbes. This community of bacteria — a drinking-water microbiome — may even be as complex as the one in your gut.
In fact, the success of probiotic therapies in treating the notorious gut infection caused by Clostridium difficile bacteria inspired Dr. Pruden, a professor of civil and environmental engineering, to think of probiotic applications in her own field. Fecal transplants are successful in treating over 90% of antibiotic-resistant cases of C. diff infection and work by restoring healthy gut microbes; use of antibiotics is thought to exacerbate the infection in part by destroying these ‘good’ gut bacteria and thus allowing pathogenic bacteria to thrive. “This got me thinking that it really may be the same thing with pipes,” says Dr. Pruden. “Variation in disinfection or water chemistry factors may contribute to the water ecology shifting in a way to favor opportunistic pathogens…perhaps there are ways to shift that ecology back.”
Opportunistic pathogens are those that tend to infect people with weaker immune systems, such as the sick, hospitalized or elderly. With cholera and typhoid-causing bacteria largely under control thanks to water-treatment advances, opportunistic pathogens — including Legionella pneumophila, which can cause a deadly form of pneumonia, and Pseudomonas aeruginosa, a common cause of infection in hospitalized patients — are now taking much of the blame for waterborne disease outbreaks in developed countries. There are millions of cases of waterborne illnesses each year in the United States, totaling almost one billion in hospitalization costs.
Complete eradication of these bacteria is unrealistic, the researchers say in their review. Just as the use and misuse of antibiotics have led to proliferation of antibiotic-resistant bacteria, the use of disinfection agents may create an environment selective for those bacteria that are resistant to the agent. Other methods, such as the use of high temperatures to kill microbes, also face the challenge posed by bacterial evolutionary capabilities — the emergence of heat-resistant bacteria. Some disinfectants can cause damage to plumbing infrastructure such as corrosion and pipe leaks, or generate unwanted byproducts.
“A far more elegant and sustainable approach is to learn to live with microbiology,” says Dr. Kyle Bibby, a professor at University of Pittsburgh’s School of Engineering who also studies environmental microbial populations. The goal of the probiotic approach is not to destroy the microbiome in our drinking water, but tweak it to select for a desirable microbial ecology, one that it is inhospitable to the growth of pathogenic bacteria. Proposed strategies include “precolonizing” plumbing pipes with nonharmful bacteria, which would compete with harmful bacteria for nutrients and thus make it harder for them to survive. Some bacterial species have been found to secrete toxins that kill Legionella pneumophila, and growth of these could be encouraged. Another strategy would target free-living amoebae, which support the growth of several types of pathogenic bacteria.
Focusing on plumbing systems in buildings (versus industrial plumbing, such as that at your local power plant), Dr. Pruden and her team are now working to more fully understand how factors such as stainless steel flange pipe material, water flow, and temperature affect the make-up of microbiomes in our plumbing. This will then contribute to understanding how conditions can be selected to favor the growth of certain bacteria and how the microbiome will be altered by introduction of additional nonnative species. “The most difficult part is the complexity,” says Dr. Pruden. “I have been amazed to see how the drinking water chemistry in every part of the country is a bit different, and these small differences can have profound effects on the drinking water microbiome.”
Research priorities and practicalities aside, the researchers also mention that there may be “aesthetic and psychological challenges” in convincing the public that inoculating plumbing systems with microbes is a good idea. But we can all agree on the necessity of clean water, and it’s exciting to think about the potential of this research to lead to an effective and sustainable approach to plumbing. Thoughts on drinking ‘probiotic water’? Let us know in the comments below!