Microbial source tracking (MST) describes a suite of methods and an investigative strategy for determination of fecal pollution sources in environmental waters that rely on the association of certain fecal microorganisms with a particular host. MST is used to assess recreational water quality and associated human health risk, and total maximum daily load allocations. Many methods rely on signature molecules (markers) such as DNA sequences of host-associated microorganisms. Human sewage pollution is among the greatest concerns for human health due to (1) the known risk of exposure to human waste and (2) the public and regulatory will to reduce sewage pollution; however, methods to identify animal sources are receiving increasing attention as our understanding of zoonotic disease potential improves. Here, we review the performance of MST methods in initial reports and field studies, with particular emphasis on quantitative PCR (qPCR). Relationships among human-associated MST markers, fecal indicator bacteria, pathogens, and human health outcomes are presented along with recommendations for future research. An integrated understanding of the advantages and drawbacks of the many MST methods targeting human sources advanced over the past several decades will benefit managers, regulators, researchers, and other users of this rapidly growing area of environmental microbiology.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1574-6976.12031

Microbial source tracking markers for detection of fecal contamination in environmental waters: relationships between pathogens and human health outcomes

Water-borne pathogen contamination in water resources and related diseases are a major water quality concern throughout the world. Increasing interest in controlling water-borne pathogens in water resources evidenced by a large number of recent publications clearly attests to the need for studies that synthesize knowledge from multiple fields covering comparative aspects of pathogen contamination, and unify them in a single place in order to present and address the problem as a whole. Providing a broader perceptive of pathogen contamination in freshwater (rivers, lakes, reservoirs, groundwater) and saline water (estuaries and coastal waters) resources, this review paper attempts to develop the first comprehensive single source of existing information on pathogen contamination in multiple types of water resources. In addition, a comprehensive discussion describes the challenges associated with using indicator organisms. Potential impacts of water resources development on pathogen contamination as well as challenges that lie ahead for addressing pathogen contamination are also discussed.

/pdf/contamination-of-water-resources-by-pathogenic-bacteria-33pi9jv47t.pdf

Contamination of water resources by pathogenic bacteria

Review on heterogeneous photocatalytic disinfection of waterborne, airborne, and foodborne viruses: Can we win against pathogenic viruses?

Detection of the human specific Bacteroides genetic marker provides evidence of widespread sewage contamination of stormwater in the urban environment

In the United States, total maximum daily load standards for bodies of water that do not meet bacterial water quality standards are set by each state. The presence of human polyomaviruses (HPyVs) can be used as an indicator of human-associated sewage pollution in these waters. We have developed and optimized a TaqMan quantitative PCR (QPCR) assay based on the conserved T antigen to both quantify and simultaneously detect two HPyVs; JC virus and BK virus. The QPCR assay was able to consistently quantify ≥10 gene copies per reaction and is linear over 5 orders of magnitude. HPyVs were consistently detected in human waste samples (57 of 64) and environmental waters with known human fecal contamination (5 of 5) and were not amplified in DNA extracted from 127 animal waste samples from 14 species. HPyV concentrations in sewage decreased 81.2 and 84.2% over 28 days incubation at 25 and 35°C, respectively. HPyVs results were compared to Escherichia coli, fecal coliform, and enterococci concentrations and the presence of three other human-associated microbes: Bacteroidetes, Methanobrevibacter smithii, and adenovirus. HPyVs were the most frequently detected of these in human and contaminated environmental samples and were more human specific than the Bacteroidetes (HF183) or M. smithii. HPyVs and M. smithii more closely mimicked the persistence of adenovirus in sewage than the other microbes. The use of this rapid and quantitative assay in water quality research could help regulatory agencies to identify sources of water pollution for improved remediation of contaminated waters and ultimately protect humans from exposure to pathogens.

Quantification of Human Polyomaviruses JC Virus and BK Virus by TaqMan Quantitative PCR and Comparison to Other Water Quality Indicators in Water and Fecal Samples

A serious concern for managers of water resources, pathogens in the urban environment easily enter waters through a number of pathways, including discharge of inadequately treated sewage, stormwater runoff, combined sewer overflows and sanitary sewer overflows. Pathogens in US ambient water bodies are regulated under the Clean Water Act (CWA), while pathogens in drinking water supplies are regulated under the Safe Drinking Water Act. Total maximum daily loads (TMDLs) are developed in accordance with CWA regulations for ambient water bodies with bacterial concentrations exceeding the water quality standard, which generally is a measure of a bacterial indicator organism. However, developing a TMDL for a supplementary indicator or pathogen is also required if a use impairment would still exist even after the water body is in compliance with the standard. This occurs because indicator organisms do not reflect the presence of pathogen contamination with complete certainty. The evaluation of pathogen indicators and summary of epidemiological studies presented are resources for those developing TMDLs to achieve water quality standards and restore water bodies to their intended uses.

http://lshs.tamu.edu/docs/lshs/end-notes/waterborne pathogens in urban watersheds-1055183618/waterborne pathogens in urban watersheds.pdf

Waterborne pathogens in urban watersheds.

Since the first identified Cryptosporidium outbreaks occurred in the 1980s and the massive 1993 Milwaukee, WI outbreak affected more than 400,000 people, the concern over the public health risks linked to protozoan pathogens Cryptosporidium and Giardia has grown. Cryptosporidium and Giardia, found in streams, rivers, groundwater, and soil, form hardy, disinfection-resistant oocysts and cysts. Both organisms are recognized causative agents of gastrointestinal illnesses linked to the consumption of contaminated surface or groundwater. This study, the first in a planned series to estimate the urban contribution to the total Cryptosporidium and Giardia receiving-water loads, focused on combined sewer overflow (CSO). CSOs are discharges of mixed untreated sewage and stormwater released directly into receiving waters during rainfall. This engineered relief is necessary to accommodate hydraulic strain when the combined rain and sanitary flows exceed the system capacity. Limited comprehensive data are available assessing the CSO discharge contribution as a source of these two pathogens. Works by States et al. and Gibson et al. each found Cryptosporidium and much greater Giardia concentrations in CSOs draining parts of Pittsburgh, PA. This project estimated the relative detection frequency and concentration of Cryptosporidium and Giardia in CSO. Analytical results were obtained using a modification of Method 1623, originally developed for much cleaner environmental samples. These data are useful for drinking water treatment plants located downstream of CSOs. It is also significant in determining the potential concentrations of parasites at treatment plant intakes and for assessing health risks for water contact and fishing activities. Commonly monitored indicator organisms (total coliform, fecal coliform, E. coli, Enterococcus, and fecal streptococcus), endospores, and selected physical and chemical parameters were analyzed to further describe the samples. CSO from urban areas was not found to be a significant contributor of Cryptosporidium, however, it was found to be a Giardia source.

Evaluating Cryptosporidium and Giardia concentrations in combined sewer overflow.

Since the first identified Cryptosporidium outbreaks occurred in the 1980s and the massive 1993 Milwaukee, WI outbreak affected more than 400,000 people (Fox & Lytle 1996), the concern over the public health risks related to protozoan pathogens Cryptosporidium and Giardia has grown. Both organisms are recognized causative agents of gastrointestinal illnesses linked to the consumption of contaminated surface or groundwater. This study, part of a planned series to estimate the urban contribution to the total Cryptosporidium and Giardia load to surface waters, focused on combined sewer overflow (CSO) and stormwater. Limited data had been available for assessing the loads of these two pathogens in CSOs. CSO samples were collected from six outfalls in five municipalities in the U.S. and analyzed using a modified U.S. EPA Method 1623 that addressed the high solids content of CSO. Results showed that CSO from urban areas was not a significant contributor of Cryptosporidium to surface waters; it was found to be a Giardia source. Stormwater samples were collected from three stormwater outfalls. Each outfall was sampled during two separate rain events. Sample locations were chosen based on United States Geological Society (USGS) land use/land cover classifications. Cryptosporidium was found in small quantities at 50% of the locations, and Giardia was significantly found at 75% of the locations.

Russell D. Arnone

Papers

Waterborne pathogens in urban watersheds.

Evaluating Cryptosporidium and Giardia concentrations in combined sewer overflow.

Investigation of Cryptosporidium and Giardia Concentrations in Combined Sewer Overflow and Stormwater Runoff