By Kelly A. Reynolds, MSPH, Ph.D.

Each year, for the last 104 years, microbiologists have gathered at the General Meeting of the American Society for Microbiology (ASM). This year, the event was held May 23-27 in New Orleans and offered a glimpse into the future of microbiology, disease trends and research priorities. The meeting was well attended (in excess of 13,000 registered) by both clinical and environmental researchers two groups you may expect to collaborate frequently but often don’t. A major theme among clinicians was the concern of emerging pathogens, primarily those resistant to antibiotic treatment. One symposium introduced the frequency of drug resistance while a drug company representative discussed the slow process of creating new, effective drugs.

In the end, conveners summarized the problem of treatment-resistant pathogens by using terms like “a losing battle,” “the bacteria are winning,” and even “Armageddon.” The environmental microbiology seminars offered more hope since efforts to identify pathogen routes of transmission and recognize emerging pathogens using new, improved monitoring technologies suggest we have options for intervention to prevent initial infections. Although debates continue as to the relative significance of pathogen transmission routes, i.e., food, water, air, person-to-person, the waterborne route is one that’s amenable to effective treatment and purification measures, whereas other routes can be more difficult to control.

Historical awareness
In the history of drinking water safety, 1974 was a landmark year that saw the establishment of the Safe Drinking Water Act (SDWA). With the SDWA, the U.S. Environmental Protection Agency (USEPA) aimed to better ensure the quality of drinking water in the country by establishing public health-related regulatory standards that all owners or operators of public water systems were required to meet. Over the last 30 years, much has changed in our awareness of the safety of drinking water and priority contaminants; hence, water quality standards continue to evolve. In accordance with the 1996 SDWA amendments, the USEPA continues to examine candidate drinking water contaminants for either regulation or further study.

Over the last decade, in particular, the tools used in environmental microbiology have changed dramatically, shifting from laborious and time-consuming cultural methods and surrogate monitoring to common use of highly advanced genetic techniques for near real-time analysis of direct pathogen presence. Advances in direct monitoring have led to more frequent identification of pathogens (viruses, bacteria and protozoa) in finished drinking water and drinking water sources, but have possibly raised more questions than they have answered.

Evaluating risks
As the sensitivity of detection methods used in water monitoring improve, are we prepared to recognize or even accept the presence of pathogens in treated water? What does the presence of pathogen genomes in drinking water mean with respect to public health risk, i.e., infection, illness, or even death? What safeguards are/should be in place to ensure the microbial safety of drinking water?

These and many other issues were discussed at an ASM symposium entitled “Advances in Understanding Microbial Exposure and Risk of Drinking Water.” A selection of distinguished researchers from industry and academia discussed current and future trends for evaluating drinking water quality and implementation of control measures for drinking water safety. Each of the presenters set the stage for what are sure to be some of the major issues in drinking water disease transmission in the near future including uncertainties with water intrusion events and distribution system contamination, the pros and cons of alternative water treatment options, emerging and treatment-resistant pathogens, and increased risks of morbidity and mortality among immunocompromised populations exposed to waterborne pathogens.

Beyond the revolution
Molecular, i.e., genomic-based, detection methods are commonplace today in research institutions and many water quality monitoring laboratories. These methods have revolutionized the field of environmental monitoring for microbes, providing direct evidence of pathogen presence rather than relying on faulty indicator systems. Although less expensive than many conventional cultural methods, molecular methods are still costly and sometimes problematic, prone to both false positive and false negative results as well as uncertainties with respect to true risk of exposure and illness (non-viable organisms also produce positive results). In addition, any monitoring results from select areas may not be correctly extrapolated to other areas in the country or even over seasonal variations where water quality parameters are ever changing.

Gaining acceptance is the use of mathematical models, based largely on current data of the likelihood of pathogen exposure and dose-response outcomes. These models aid in the assessment of the potential health risks associated with a specific pathogen present in the environment and may utilize cross-disciplinary tools of microbiology, epidemiology and mathematics. Taking this one step further, researchers at Michigan State University are developing the concept of Virulence Factors Activity Relationships (VFARs) to prioritize microbial drinking water contaminants. This effort involves the development of a database of genetic elements—i.e., surface proteins, toxins, attachment factors, metabolic pathways and invasion factors—associated with microbial pathogens that could code for increased virulence. In other words, utilizing the tools of molecular biology, researchers are evaluating if risk can be estimated based on organism sequence.

Finally, who is at risk? How well are our studies designed to evaluate the national burden of waterborne disease? How can we use studies of specific populations and extrapolate their risk to the whole U.S. population with inherent physical and spatial variability? We know epidemiology (population-based) studies are difficult to extrapolate data from due to confounding factors that could inadvertently bias the results, for example, the placebo effect. In addition, we have very limited data on the most at-risk populations, such as children and the elderly. Furthermore, what are the cost-benefits of additional water purification vs. disease treatment in healthy populations and immunocompromised populations?

Conclusion
Of great interest to the water treatment industry is the question of whether or not point-of-use or point-of-entry (POU/POE) treatment systems not only improve the taste and aesthetics of water, but have a significant impact on the reduction of morbidity or mortality. Studies are currently under way to determine the variable health impacts of differing source water quality, treatment courses and population susceptibilities. These are all issues that the research community is focusing on now and will continue to evaluate in the near future. Table 1 outlines the topics discussed in the ASM symposium that are sure to be focal areas for continued research in monitoring, control and prevention of waterborne disease.

About the author
Dr. Kelly A. Reynolds is a research scientist at the University of Arizona with a focus on development of rapid methods for detecting human pathogenic viruses in drinking water. She holds a master of science degree in public health (MSPH) from the University of South Florida and doctorate in microbiology from the University of Arizona. Reynolds has also been a member of the WC&P Technical Review Committee since 1997.

 

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