Relative inactivation of faecal indicator bacteria and sewage markers in freshwater and seawater microcosms

Ahmed, Warish; Gyawali, Pradip; Sidhu, J. P. S.; Toze, Simon

doi:10.1111/lam.12285

Cited by 60 publications

(50 citation statements)

References 32 publications

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“…In this study, as in many others (28,30,(54)(55)(56)(57)(58), inactivation of FIB exposed to sunlight is significantly faster than that of bacteria kept in the dark in both freshwater and marine water matrixes. In our sunlight-exposed microcosms, concentrations of enterococci and E. coli were reduced 90% in Յ2.1 h. The observed inactivation rates were higher than those in studies conducted in temperate climates in the United States and New Zealand (28,30,57,59) but similar to those observed in subtropical regions of Australia (25), indicating that regional differences exist. Greater solar intensity and higher water temperatures are likely the dominant contributing factors.…”

Section: Discussionmentioning

confidence: 52%

See 1 more Smart Citation

Human-Associated Bacteroides spp. and Human Polyomaviruses as Microbial Source Tracking Markers in Hawaii

Kirs

Caffaro-Filho

Wong

et al. 2016

Appl Environ Microbiol

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Identification of sources of fecal contaminants is needed to (i) determine the health risk associated with recreational water use and (ii) implement appropriate management practices to mitigate this risk and protect the environment. This study evaluated human-associated Bacteroides spp. (HF183TaqMan) and human polyomavirus (HPyV) markers for host sensitivity and specificity using human and animal fecal samples collected in Hawaii. The decay rates of those markers and indicator bacteria were identified in marine and freshwater microcosms exposed and not exposed to sunlight, followed by field testing of the usability of the molecular markers. Both markers were strongly associated with sewage, although the cross-reactivity of the HF183TaqMan (also present in 82% of canine [n ‫؍‬ 11], 30% of mongoose [n ‫؍‬ 10], and 10% of feline [n ‫؍‬ 10] samples) needs to be considered. Concentrations of HF183TaqMan in human fecal samples exceeded those in cross-reactive animals at least 1,000-fold. In the absence of sunlight, the decay rates of both markers were comparable to the die-off rates of enterococci in experimental freshwater and marine water microcosms. However, in sunlight, the decay rates of both markers were significantly lower than the decay rate of enterococci. While both markers have their individual limitations in terms of sensitivity and specificity, these limitations can be mitigated by using both markers simultaneously; ergo, this study supports the concurrent use of HF183TaqMan and HPyV markers for the detection of sewage contamination in coastal and inland waters in Hawaii. IMPORTANCEThis study represents an in-depth characterization of microbial source tracking (MST) markers in Hawaii. The distribution and concentrations of HF183TaqMan and HPyV markers in human and animal fecal samples and in wastewater, coupled with decay data obtained from sunlight-exposed and unexposed microcosms, support the concurrent application of HF183TaqMan and HPyV markers for sewage contamination detection in Hawaii waters. Both markers are more conservative and more specific markers of sewage than fecal indicator bacteria (enterococci and Escherichia coli). Analysis of HF183TaqMan (or newer derivatives) is recommended for inclusion in future epidemiological studies concerned with beach water quality, while better concentration techniques are needed for HPyV. Such epidemiological studies can be used to develop new recreational water quality criteria, which will provide direct information on the absence or presence of sewage contamination in water samples as well as reliable measurements of the risk of waterborne disease transmission to swimmers. T he recently revised recreational water quality criteria (1) continue to use concentrations of fecal indicator bacteria (FIB), such as enterococci and Escherichia coli, to determine risks to swimmers and to establish recreational water quality standards. However, major limitations in the implementation of the current recreational water quality standards are related to the fact t...

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Section: Discussionmentioning

confidence: 52%

“…Environmental differences, such as sunlight, water temperatures, etc., vary on the regional scale. While studies of decay rates of different molecular source-specific markers are starting to emerge (25)(26)(27)(28)(29)(30)(31)(32), relatively little is known about the decay rates of markers in tropical waters. Human-associated Bacteroides spp.…”

mentioning

confidence: 99%

Human-Associated Bacteroides spp. and Human Polyomaviruses as Microbial Source Tracking Markers in Hawaii

Kirs

Caffaro-Filho

Wong

et al. 2016

Appl Environ Microbiol

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“…This is particularly important for water quality regulation and health risk context.Several studies reported that the decay of the Bacteroidales DNA markers in water is comparable to culturable FIB [103,105,108,115,116]. These findings emphasize the potential for using Bacteroidales marker for MST field studies.…”

Section: Decay Of Human-specific Bacteroides Markers In Environmentalmentioning

confidence: 57%

Current Status of Marker Genes of Bacteroides and Related Taxa for Identifying Sewage Pollution in Environmental Waters

Ahmed

Hughes

Harwood

2016

Water

112

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Abstract:Microbial source tracking (MST) endeavors to determine sources of fecal pollution in environmental waters by capitalizing on the association of certain microorganisms with the gastrointestinal tract and feces of specific animal groups. Several decades of research have shown that bacteria belonging to the gut-associated order Bacteroidales, and particularly the genus Bacteroides, tend to co-evolve with the host, and are, therefore, particularly suitable candidates for MST applications. This review summarizes the current research on MST methods that employ genes belonging to Bacteroidales/Bacteroides as tracers or "markers" of sewage pollution, including known advantages and deficiencies of the many polymerase chain reaction (PCR)-based methods that have been published since 2000. Host specificity is a paramount criterion for confidence that detection of a marker is a true indicator of the target host. Host sensitivity, or the prevalence of the marker in feces/waste from the target host, is necessary for confidence that absence of the marker is indicative of the absence of the pollution source. Each of these parameters can vary widely depending on the type of waste assessed and the geographic location. Differential decay characteristics of bacterial targets and their associated DNA contribute to challenges in interpreting MST results in the context of human health risks. The HF183 marker, derived from the 16S rRNA gene of Bacteroides dorei and closely related taxa, has been used for almost two decades in MST studies, and is well characterized regarding host sensitivity and specificity, and in prevalence and concentration in sewage in many countries. Other markers such as HumM2 and HumM3 show promise, but require further performance testing to demonstrate their widespread utility. An important limitation of the one-marker-one-assay approach commonly used for MST is that given the complexities of microbial persistence in environmental waters, and the methodological challenges of quantitative PCR (qPCR) in such samples, the absence of a given marker does not ensure the absence of fecal pollution in the source water. Approaches under development, such as microarray and community analysis, have the potential to improve MST practices, thereby increasing our ability to protect human and ecosystem health.

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“…These findings are in line with Boehm et al (2012) who reported a T90 of 0.017 to 0.025 for Salmonella in saltwater under sunlight conditions. Ahmed et al (2014) conducted experiments in both freshwater and saltwater microcosms, they found that the fecal indicators enterococci, E.coli, and the microbial source tracking marker (MST) human Bacteroides (HF183) had a slightly faster inactivation rate in saltwater than freshwater (although not statistically significant). The Bacteroides marker had a similar decay rate as the fecal indicator organisms suggesting that it might be a reasonable indicator of recent fecal contamination (Ahmed et al, 2014).…”

Section: Bacteria and Bacterial Indicatorsmentioning

confidence: 99%

Persistence of Pathogens in Sewage and Other Water Types

Murphy¹

2019

Water and Sanitation for the 21st Century: Health and Microbiological Aspects of Excreta and Wastewater Management (Global Wate

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Relative inactivation of faecal indicator bacteria and sewage markers in freshwater and seawater microcosms

Cited by 60 publications

References 32 publications

Human-Associated Bacteroides spp. and Human Polyomaviruses as Microbial Source Tracking Markers in Hawaii

Human-Associated Bacteroides spp. and Human Polyomaviruses as Microbial Source Tracking Markers in Hawaii

Current Status of Marker Genes of Bacteroides and Related Taxa for Identifying Sewage Pollution in Environmental Waters

Persistence of Pathogens in Sewage and Other Water Types

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