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Pachepsky Y, Harriger MD, Panko Graff C, Wyatt-Brown L, Stocker MD, Smith JE. Multiscale spatiotemporal variability of fecal indicator bacteria and associated particle size distributions in the sandy bottom sediments of a Pennsylvania creek. JOURNAL OF ENVIRONMENTAL QUALITY 2024; 53:101-111. [PMID: 37949440 DOI: 10.1002/jeq2.20531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 10/05/2023] [Accepted: 11/03/2023] [Indexed: 11/12/2023]
Abstract
Concentrations of the fecal indicator bacteria (FIB) Escherichia coli and enterococci are used to assess microbial impairment in irrigation and recreation water sources. Although the FIB concentrations' variability at large temporal scales, such as seasons, and large spatial scales encompassing different land use has been studied, the knowledge about smaller scale variability remains sparse. This work aimed to research the small-scale variability of E. coli and enterococci in a montane creek with sandy bottom sediments. Sediment samples were collected weekly for a year in triplicate at sampling sites in a forested headwater, an agricultural area, and a mixed urban-agricultural area. The average weekly change in concentrations was from two times at the forested site to five times at the urban-agricultural site. Mean relative deviations from averages across sampling locations increased from -25% at the forested site to 45% at the urban-agricultural site. This trend was also observed separately over the cold and warm seasons. Over a week without precipitation, E. coli concentrations decreased on average by 20% in warm period and by 45% in cold period; the enterococci concentration declined by 12% in both cold and warm periods. The sediment particle size distributions were significantly different among the three sites and between the cold and warm seasons. Rankings of sediment fine mass fractions and FIB concentrations were positively correlated at two of three sampling sites in more than 70% of observation dates. The results of this work indicate the need to evaluate the uncertainty of sediment FIB concentrations before designing sediment FIB monitoring quality.
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Affiliation(s)
- Yakov Pachepsky
- USDA-ARS Environmental Microbial and Food Safety Laboratory, Beltsville, Maryland, USA
| | - M D Harriger
- Biology Department, Harrisburg University of Science and Technology, Harrisburg, Pennsylvania, USA
| | | | - Lauren Wyatt-Brown
- Department of Environmental Science & Technology, University of Maryland College Park, College Park, Maryland, USA
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Rothenberg SE, Furrer JM, Ingram LA, Ashford-Carroll TS, Foster SA, Hystad P, Hynes DM, Navab-Daneshmand T, Branscum AJ, Kruearat P. Sanitary sewage overflows, boil water advisories, and emergency room and urgent care visits for gastrointestinal illness: a case-crossover study in South Carolina, USA, 2013-2017. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2023; 33:102-110. [PMID: 36376586 PMCID: PMC9851942 DOI: 10.1038/s41370-022-00498-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 11/01/2022] [Accepted: 11/02/2022] [Indexed: 05/16/2023]
Abstract
BACKGROUND Sanitary sewage overflows (SSOs) release raw sewage, which may contaminate the drinking water supply. Boil water advisories (BWAs) are issued during low or negative pressure events, alerting customers to potential contamination in the drinking water distribution system. OBJECTIVE We evaluated the associations between SSOs and BWAs and diagnoses of gastrointestinal (GI) illness in Columbia, South Carolina, and neighboring communities, 2013-2017. METHODS A symmetric bi-directional case-crossover study design was used to assess the role of SSOs and BWAs on Emergency Room and Urgent Care visits with a primary diagnosis of GI illness. Cases were considered exposed if an SSO or BWA occurred 0-4 days, 5-9 days, or 10-14 days prior to the diagnosis, within the same residential zip code. Effect modification was explored via stratification on participant-level factors (e.g., sex, race, age) and season (January-March versus April-December). RESULTS There were 830 SSOs, 423 BWAs, and 25,969 cases of GI illness. Highest numbers of SSOs, BWAs and GI cases were observed in a zip code where >80% of residents identified as Black or African-American. SSOs were associated with a 13% increase in the odds of a diagnosis for GI illness during the 0-4 day hazard period, compared to control periods (Odds Ratio: 1.13, 95% Confidence Interval: 1.09, 1.18), while no associations were observed during the other hazard periods. BWAs were not associated with increased or decreased odds of GI illness during all three hazard periods. However, in stratified analyses BWAs issued between January-March were associated with higher odds of GI illness, compared to advisories issued between April-December, in all three hazard periods. SIGNIFICANCE SSOs (all months) and BWAs (January-March) were associated with increased odds of a diagnosis of GI illness. Future research should examine sewage contamination of the drinking water distribution system, and mechanisms of sewage intrusion from SSOs. IMPACT Sewage contains pathogens, which cause gastrointestinal (GI) illness. In Columbia, South Carolina, USA, between 2013-2017, there were 830 sanitary sewage overflows (SSOs). There were also 423 boil water advisories, which were issued during negative pressure events. Using case-crossover design, SSOs (all months) and boil water advisories (January-March) were associated with increased odds of Emergency Room and Urgent Care diagnoses of GI illness, potentially due to contamination of the drinking water distribution system. Lastly, we identified a community where >80% of residents identified as Black or African-American, which experienced a disproportionate burden of sewage exposure, compared to the rest of Columbia.
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Affiliation(s)
- Sarah E Rothenberg
- Oregon State University, College of Public Health and Human Sciences, Corvallis, OR, 97331, USA.
| | - Jessica M Furrer
- Benedict College, Department of Computer Science, Physics, and Engineering, Columbia, SC, 29204, USA
| | - Lucy A Ingram
- University of South Carolina, Arnold School of Public Health, Columbia, SC, 29208, USA
| | | | - Stephanie A Foster
- Oregon State University, College of Public Health and Human Sciences, Corvallis, OR, 97331, USA
| | - Perry Hystad
- Oregon State University, College of Public Health and Human Sciences, Corvallis, OR, 97331, USA
| | - Denise M Hynes
- Oregon State University, College of Public Health and Human Sciences, Corvallis, OR, 97331, USA
- Oregon State University, Center for Quantitative Life Sciences, Corvallis, OR, 97331, USA
- US Department of Veterans Affairs, VA Portland Health Care System, Center to Improve Veteran Involvement in Care, Portland, OR, 97239, USA
| | | | - Adam J Branscum
- Oregon State University, College of Public Health and Human Sciences, Corvallis, OR, 97331, USA
| | - Pemika Kruearat
- Oregon State University, College of Public Health and Human Sciences, Corvallis, OR, 97331, USA
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Stocker MD, Smith JE, Hill RL, Pachepsky YA. Intra-daily variation of Escherichia coli concentrations in agricultural irrigation ponds. JOURNAL OF ENVIRONMENTAL QUALITY 2022; 51:719-730. [PMID: 35419843 DOI: 10.1002/jeq2.20352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 03/22/2022] [Indexed: 06/14/2023]
Abstract
Microbial water quality is determined by comparing observed Escherichia coli concentrations with regulatory thresholds. Measured concentrations can be expected to change throughout the course of a day in response to diurnal variation in environmental conditions, such as solar radiation and temperature. Therefore, the time of day at which samples are taken is an important factor within microbial water quality measurements. However, little is known about the diurnal variations of E. coli concentrations in surface sources of irrigation water. The objectives of this work were to evaluate the intra-daily dynamics of E. coli in three irrigation ponds in Maryland over several years and to determine the water quality parameters to which E. coli populations are most sensitive. Water sampling was conducted across the ponds at 0900, 1200, and 1500 h on a total of 17 dates in the summers of 2019-2021. One-way ANOVA revealed significant diurnal variability in E. coli concentrations in Pond (P)1 and P2, whereas no significant effects were observed in P3. Escherichia coli die-off rates calculated between sampling time points in the same day were significantly higher in P2 than in P1 and P3, and these rates ranged from 0.005 to 0.799 h-1 across ponds. Concentrations of dissolved oxygen, pH, conductivity, and turbidity exerted the most control over E. coli populations. Results of this work demonstrate that sampling in the early-morning hours provides the most conservative assessment of the microbial quality of irrigation waters.
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Affiliation(s)
- Matthew D Stocker
- Oak Ridge Institute for Science and Education, Oak Ridge, TN, 37830, USA
- USDA-ARS Environmental Microbial and Food Safety Laboratory, Beltsville, MD, 20705, USA
- Dep. of Environmental Science and Technology, Univ. of Maryland, College Park, MD, 20742, USA
| | - Jaclyn E Smith
- Oak Ridge Institute for Science and Education, Oak Ridge, TN, 37830, USA
- USDA-ARS Environmental Microbial and Food Safety Laboratory, Beltsville, MD, 20705, USA
- Dep. of Environmental Science and Technology, Univ. of Maryland, College Park, MD, 20742, USA
| | - Robert L Hill
- Dep. of Environmental Science and Technology, Univ. of Maryland, College Park, MD, 20742, USA
| | - Yakov A Pachepsky
- USDA-ARS Environmental Microbial and Food Safety Laboratory, Beltsville, MD, 20705, USA
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Stocker MD, Pachepsky YA, Hill RL. Prediction of E. coli Concentrations in Agricultural Pond Waters: Application and Comparison of Machine Learning Algorithms. Front Artif Intell 2022; 4:768650. [PMID: 35088045 PMCID: PMC8787305 DOI: 10.3389/frai.2021.768650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 12/13/2021] [Indexed: 11/13/2022] Open
Abstract
The microbial quality of irrigation water is an important issue as the use of contaminated waters has been linked to several foodborne outbreaks. To expedite microbial water quality determinations, many researchers estimate concentrations of the microbial contamination indicator Escherichia coli (E. coli) from the concentrations of physiochemical water quality parameters. However, these relationships are often non-linear and exhibit changes above or below certain threshold values. Machine learning (ML) algorithms have been shown to make accurate predictions in datasets with complex relationships. The purpose of this work was to evaluate several ML models for the prediction of E. coli in agricultural pond waters. Two ponds in Maryland were monitored from 2016 to 2018 during the irrigation season. E. coli concentrations along with 12 other water quality parameters were measured in water samples. The resulting datasets were used to predict E. coli using stochastic gradient boosting (SGB) machines, random forest (RF), support vector machines (SVM), and k-nearest neighbor (kNN) algorithms. The RF model provided the lowest RMSE value for predicted E. coli concentrations in both ponds in individual years and over consecutive years in almost all cases. For individual years, the RMSE of the predicted E. coli concentrations (log10 CFU 100 ml-1) ranged from 0.244 to 0.346 and 0.304 to 0.418 for Pond 1 and 2, respectively. For the 3-year datasets, these values were 0.334 and 0.381 for Pond 1 and 2, respectively. In most cases there was no significant difference (P > 0.05) between the RMSE of RF and other ML models when these RMSE were treated as statistics derived from 10-fold cross-validation performed with five repeats. Important E. coli predictors were turbidity, dissolved organic matter content, specific conductance, chlorophyll concentration, and temperature. Model predictive performance did not significantly differ when 5 predictors were used vs. 8 or 12, indicating that more tedious and costly measurements provide no substantial improvement in the predictive accuracy of the evaluated algorithms.
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Affiliation(s)
- Matthew D. Stocker
- Environmental Microbial and Food Safety Laboratory, United States Department of Agriculture–Agricultural Research Service, Beltsville, MD, United States
- Oak Ridge Institute for Science and Education, Oak Ridge, TN, United States
- Department of Environmental Science and Technology, University of Maryland, College Park, MD, United States
| | - Yakov A. Pachepsky
- Environmental Microbial and Food Safety Laboratory, United States Department of Agriculture–Agricultural Research Service, Beltsville, MD, United States
| | - Robert L. Hill
- Department of Environmental Science and Technology, University of Maryland, College Park, MD, United States
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Salam S, McDaniel R, Bleakley B, Amegbletor L, Mardani S. Variability of E. coli in streambed sediment and its implication for sediment sampling. JOURNAL OF CONTAMINANT HYDROLOGY 2021; 242:103859. [PMID: 34343844 DOI: 10.1016/j.jconhyd.2021.103859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 07/02/2021] [Accepted: 07/12/2021] [Indexed: 06/13/2023]
Abstract
E. coli is the number one cause for water quality impairments in rivers and streams in South Dakota and the United States. Stream bottom sediments can be a reservoir for bacteria, including pathogenic organisms and fecal indicator bacteria (FIB), due to the favorable conditions provided by sediments for survival. Despite this, little is known about the variability of E. coli in sediments which should be considered when developing a sampling regime. This study examines the spatial variability of E. coli in sediment across the stream cross-section, the temporal stability of E. coli in sediment samples, and the implications for sediment sampling and processing. Five locations were sampled for sediment E. coli along two tributaries to the Big Sioux River in eastern South Dakota, four along Skunk Creek (Sk1, Sk2, Sk3, and Sk4), and one in Sixmile Creek (SM). In Skunk Creek, site Sk1 has direct cattle access where the other three sites (Sk2, Sk3, and Sk4) are under Seasonal Riparian Area Management (SRAM), a strategy that limits the cattle access to the stream. E. coli concentrations in the sediment ranged from 4 to 997 CFU g-1 (8.5 × 102 to 2.1 × 105 CFU 100 mL-1). The highest and lowest E. coli concentrations observed were at sites Sk1 and Sk4, respectively. The E. coli concentration decreased from the upstream cattle crossing site (Sk1) through the downstream SRAM sites. Analyzing the stream cross-section analysis revealed no significant difference in E. coli concentration between the edge and the middle of the stream. Sediment samples can be held up to 24 h after sample collection in refrigerated conditions (37 °F) in the majority of cases (80%) without significant changes in E. coli concentrations. The sample size analysis indicated the spatial variability of E. coli across the stream cross-section is high and a single grab sample may not be able to provide adequate representation of E. coli concentrations in sediment without substantial error. The findings provide insight for designing E. coli monitoring projects and promote the awareness of unconventional sources of microbiological water quality impairment which are often overlooked.
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Affiliation(s)
- Sadia Salam
- Department of Agricultural and Biosystems Engineering, South Dakota State University, 1400 N Campus Drive, Ag & biosystems Engineering-Box 2120 University Station, Brookings, SD 57007, USA.
| | - Rachel McDaniel
- Department of Agricultural and Biosystems Engineering, South Dakota State University, 1400 N Campus Drive, Ag & biosystems Engineering-Box 2120 University Station, Brookings, SD 57007, USA
| | - Bruce Bleakley
- Department of Biology and Microbiology, South Dakota State University, Alfred Dairy Science Hall 220 Biology & Microbiology-Box 2104A, University Station, Brookings, SD 57007, USA
| | - Louis Amegbletor
- Department of Agricultural and Biosystems Engineering, South Dakota State University, 1400 N Campus Drive, Ag & biosystems Engineering-Box 2120 University Station, Brookings, SD 57007, USA
| | - Sara Mardani
- Department of Agricultural and Biosystems Engineering, South Dakota State University, 1400 N Campus Drive, Ag & biosystems Engineering-Box 2120 University Station, Brookings, SD 57007, USA
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Abstract
Surface water contamination by pathogen bacteria remains a threat to public health in the rural areas of developing countries. Fecal indicator bacteria (FIB) like Escherichia coli (E. coli) are widely used to assess water contamination, but their behavior in tropical ecosystems is poorly documented. Our study focused on headwater wetlands which are likely to play a key role in stream water purification of fecal pollutants. Our main objectives were to: (i) evaluate decay rates (k) of the total, particle-attached and free-living E. coli; (ii) quantify the relative importance of solar radiation exposition and suspended particles deposition on k; and (iii) investigate E. coli survival in the deposited sediment. We installed and monitored 12 mesocosms, 4500 mL each, across the main headwater wetland of the Houay Pano catchment, northern Lao People’s Democratic Republic (Lao PDR), for 8 days. The four treatments with triplicates were: sediment deposition-light (DL); sediment deposition-dark (DD); sediment resuspension-light (RL); and sediment resuspension-dark (RD). Particle-attached bacteria predominated in all mesocosms (97 ± 6%). Decay rates ranged from 1.43 ± 0.15 to 1.17 ± 0.13 day−1 for DL and DD treatments, and from 0.50 ± 0.15 to −0.14 ± 0.37 day−1 for RL and RD treatments. Deposition processes accounted for an average of 92% of E. coli stock reduction, while solar radiation accounted for around 2% over the experiment duration. The sampling of E. coli by temporary resuspension of the deposited sediment showed k values close to zero, suggesting potential survival or even growth of bacteria in the sediment. The present findings may help parameterizing hydrological and water quality models in a tropical context.
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Hygienic Condition of Different Water Sources in the Kharaa River Basin, Mongolia in the Light of a Rapid Warming Trend. ATMOSPHERE 2020. [DOI: 10.3390/atmos11101113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mongolia is a water-scarce land-locked country, and available water resources are utilized for multiple purposes including irrigation, food preparation, drinking water for livestock and people. Limited data availability on water hygiene means that the related risks to public health are only partially understood. This is particularly problematic due to the widespread use of unimproved water sources such as surface water and water from simple shallow wells. Based on two field surveys in the Kharaa River Basin in spring 2017 and 2018, we assessed the presence and quantity of total coliforms (TC), fecal coliforms (FC), and E. coli bacteria in surface waters and wells and investigated potential linkages between temperature and hygiene. In the Kharaa River and its tributaries, TC concentrations averaged at a most probable number of (MPN) of 754 ± 761 per 100 mL and FC concentrations at an MPN of 31 ± 33. Only small and non-significant correlations between coliform concentrations and temperature were identified. Coliforms concentrations in wells were lower (average MPN for TC: 550 ± 1286, and for FC 58 ± 253). There was considerable variation between wells, with moderate but significant correlations between temperature and bacterial counts. Low water temperatures in April and May (just above freezing to less than 6.5 °C in wells and 7.5 °C to 14.5 °C in the river system) and the positive correlations between temperature and coliform concentrations particularly for well samples indicate that further warming is likely to increase the risks of microbiological water pollution. In the future, this should be complemented by modeling at a watershed scale. This should include the consideration of a trend towards stronger rainfall events, changes in livestock density, and urban sewage treatment and discharge, which are other likely drivers of changes in water hygiene.
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Devane ML, Moriarty E, Weaver L, Cookson A, Gilpin B. Fecal indicator bacteria from environmental sources; strategies for identification to improve water quality monitoring. WATER RESEARCH 2020; 185:116204. [PMID: 32745743 DOI: 10.1016/j.watres.2020.116204] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 07/13/2020] [Accepted: 07/19/2020] [Indexed: 06/11/2023]
Abstract
In tropical to temperate environments, fecal indicator bacteria (FIB), such as enterococci and Escherichia coli, can persist and potentially multiply, far removed from their natural reservoir of the animal gut. FIB isolated from environmental reservoirs such as stream sediments, beach sand and vegetation have been termed "naturalized" FIB. In addition, recent research suggests that the intestines of poikilothermic animals such as fish may be colonized by enterococci and E. coli, and therefore, these animals may contribute to FIB concentrations in the aquatic environment. Naturalized FIB that are derived from fecal inputs into the environment, and subsequently adapted to maintain their population within the non-host environment are termed "naturalized enteric FIB". In contrast, an additional theory suggests that some "naturalized" FIB diverged from enteric FIB many millions of years ago and are now normal inhabitants of the environment where they are referred to as "naturalized non-enteric FIB". In the case of the Escherichia genus, the naturalized non-enteric members are identified as E. coli during routine water quality monitoring. An over-estimation of the health risk could result when these naturalized, non-enteric FIB, (that is, not derived from avian or mammalian fecal contamination), contribute to water quality monitoring results. It has been postulated that these environmental FIB belonging to the genera Escherichia and Enterococcus can be differentiated from enteric FIB by genetic methods because they lack some of the genes required for colonization of the host intestine, and have acquired genes that aid survival in the environment. Advances in molecular tools such as next generation sequencing will aid the identification of genes peculiar or "enriched" in particular habitats to discriminate between enteric and environmental FIB. In this appraisal, we have reviewed the research studying "naturalized" FIB, and discussed the techniques for their differentiation from enteric FIB. This differentiation includes the important distinction between enteric FIB derived from fresh and non-recent fecal inputs, and those truly non-enteric environmental microbes, which are currently identified as FIB during routine water quality monitoring. The inclusion of tools for the identification of naturalized FIB (enteric or environmental) would be a valuable resource for future studies assessing water quality.
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Affiliation(s)
- Megan L Devane
- Institute of Environmental Science and Research Ltd., 27 Creyke Rd, Ilam, Christchurch, New Zealand.
| | - Elaine Moriarty
- Institute of Environmental Science and Research Ltd., 27 Creyke Rd, Ilam, Christchurch, New Zealand
| | - Louise Weaver
- Institute of Environmental Science and Research Ltd., 27 Creyke Rd, Ilam, Christchurch, New Zealand
| | - Adrian Cookson
- AgResearch Ltd., Hopkirk Research Institute, Massey University, Palmerston North, New Zealand; mEpiLab, School of Veterinary Sciences, Massey University, Palmerston North, New Zealand
| | - Brent Gilpin
- Institute of Environmental Science and Research Ltd., 27 Creyke Rd, Ilam, Christchurch, New Zealand
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Abstract
Fecal microorganisms can enter water bodies in diverse ways, including runoff, sewage discharge, and direct fecal deposition. Once in water, the microorganisms experience conditions that are very different from intestinal habitats. The transition from host to aquatic environment may lead to rapid inactivation, some degree of persistence, or growth. Microorganisms may remain planktonic, be deposited in sediment, wash up on beaches, or attach to aquatic vegetation. Each of these habitats offers a panoply of different stressors or advantages, including UV light exposure, temperature fluctuations, salinity, nutrient availability, and biotic interactions with the indigenous microbiota (e.g., predation and/or competition). The host sources of fecal microorganisms are likewise numerous, including wildlife, pets, livestock, and humans. Most of these microorganisms are unlikely to affect human health, but certain taxa can cause waterborne disease. Others signal increased probability of pathogen presence, e.g., the fecal indicator bacteria Escherichia coli and enterococci and bacteriophages, or act as fecal source identifiers (microbial source tracking markers). The effects of environmental factors on decay are frequently inconsistent across microbial species, fecal sources, and measurement strategies (e.g., culture versus molecular). Therefore, broad generalizations about the fate of fecal microorganisms in aquatic environments are problematic, compromising efforts to predict microbial decay and health risk from contamination events. This review summarizes the recent literature on decay of fecal microorganisms in aquatic environments, recognizes defensible generalizations, and identifies knowledge gaps that may provide particularly fruitful avenues for obtaining a better understanding of the fates of these organisms in aquatic environments.
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Smith JE, Kiefer LA, Stocker MD, Blaustein RA, Ingram S, Pachepsky YA. Depth-Dependent Response of Fecal Indicator Bacteria in Sediments to Changes in Water Column Nutrient Levels. JOURNAL OF ENVIRONMENTAL QUALITY 2019; 48:1074-1081. [PMID: 31589666 DOI: 10.2134/jeq2018.12.0450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Concentrations of in bottom sediments can influence the assessment of microbial stream water quality. Runoff events bring nutrients to streams that can support the growth of in sediments. The objective of this work was to evaluate depth-dependent changes in populations after nutrients are introduced to the water column. Bovine feces were collected fresh and mixed into sediment. Studies were performed in a microcosm system with continuous flow of synthetic stream water over inoculated sediment. Dilutions of autoclaved bovine manure were added to water on Day 16 at two concentrations, and KBr tracer was introduced into the water column to evaluate ion diffusion. Concentrations of , total coliforms, and total aerobic heterotrophic bacteria, along with orthophosphate-P and ammonium N, were monitored in water and sediment for 32 d. Sediment samples were analyzed in 0- to 1-cm and 1- to 3-cm sectioned depths. Concentrations of and total coliforms in top sediments were approximately one order of magnitude greater than in bottom sediments throughout the experiment. Introduction of nutrients to the water column triggered an increase of nutrient levels in both top and bottom sediments and increased concentrations of bacteria in the water. However, the added nutrients had a limited effect on in sediment where bacterial inactivation continued. Vertical gradients of concentrations in sediments persisted during the inactivation periods both before and after nutrient addition to the water column.
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Lamori JG, Xue J, Rachmadi AT, Lopez GU, Kitajima M, Gerba CP, Pepper IL, Brooks JP, Sherchan S. Removal of fecal indicator bacteria and antibiotic resistant genes in constructed wetlands. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:10188-10197. [PMID: 30758793 DOI: 10.1007/s11356-019-04468-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 02/03/2019] [Indexed: 06/09/2023]
Abstract
Wastewater discharge evidently increased bacterial diversity in the receiving waterbodies. The objective of this study was to evaluate the effectiveness of a constructed wetland in reducing fecal indicator bacteria (FIB) and antibiotic resistant genes (ARGs). We determined the prevalence and attenuation of fecal indicator bacteria including Escherichia coli and enterococci, along with ARGs, and human-associated Bacteroidales (HF183) markers by quantitative polymerase chain reaction (qPCR) method. Three types of water samples (inlet, intermediate, and outlet) from a constructed wetland were collected once a month from May to December in 2013. The overall reduction of E. coli was 50.0% based on culture method. According to the qPCR result, the overall removal rate of E. coli was only 6.7%. Enterococci were found in 62.5% of the wetland samples. HF183 genetic marker was detected in all final effluent samples with concentration ranging from 1.8 to 4.22 log10 gene copies (GC)/100 ml. Of the ARGs tested, erythromycin resistance genes (ermF) were detected in 79.2% of the wetland samples. The class 1 integrase (intI1) was detected in all water samples with concentration ranging from 0.83 to 5.54 log10 GC/100 ml. The overall removal rates of enterococci, HF183, intI1, and ermF were 84.0%, 66.6%, 67.2%, and 13.1%, respectively.
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Affiliation(s)
- Jennifer G Lamori
- Department of Global Environmental Health Sciences, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, 70112, USA
| | - Jia Xue
- Department of Global Environmental Health Sciences, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, 70112, USA
| | - Andri T Rachmadi
- Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North13 West8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan
| | - Gerardo U Lopez
- School of Animal and Comparative Biomedical Sciences, The University of Arizona, 1007 E. Lowell St., Tucson, AZ, 85721, USA
| | - Masaaki Kitajima
- Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North13 West8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan
| | - Charles P Gerba
- Department of Soil, Water and Environmental Science, The University of Arizona, 1117 E. Lowell St., Tucson, AZ, 85721, USA
| | - Ian L Pepper
- Department of Soil, Water and Environmental Science, The University of Arizona, 1117 E. Lowell St., Tucson, AZ, 85721, USA
- Water and Energy Sustainable Technology (WEST) Center, The University of Arizona, 2959 West Calle Agua Nueva, Tucson, AZ, 85745, USA
| | - John P Brooks
- Genetics and Sustainable Agriculture Unit, USDA-ARS, Mississippi State, MS, 39762, USA
| | - Samendra Sherchan
- Department of Global Environmental Health Sciences, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, 70112, USA.
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Korajkic A, McMinn BR, Harwood VJ. Relationships between Microbial Indicators and Pathogens in Recreational Water Settings. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2018; 15:E2842. [PMID: 30551597 PMCID: PMC6313479 DOI: 10.3390/ijerph15122842] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 12/10/2018] [Accepted: 12/11/2018] [Indexed: 11/16/2022]
Abstract
Fecal pollution of recreational waters can cause scenic blight and pose a threat to public health, resulting in beach advisories and closures. Fecal indicator bacteria (total and fecal coliforms, Escherichia coli, and enterococci), and alternative indicators of fecal pollution (Clostridium perfringens and bacteriophages) are routinely used in the assessment of sanitary quality of recreational waters. However, fecal indicator bacteria (FIB), and alternative indicators are found in the gastrointestinal tract of humans, and many other animals and therefore are considered general indicators of fecal pollution. As such, there is room for improvement in terms of their use for informing risk assessment and remediation strategies. Microbial source tracking (MST) genetic markers are closely associated with animal hosts and are used to identify fecal pollution sources. In this review, we examine 73 papers generated over 40 years that reported the relationship between at least one indicator and one pathogen group or species. Nearly half of the reports did not include statistical analysis, while the remainder were almost equally split between those that observed statistically significant relationships and those that did not. Statistical significance was reported less frequently in marine and brackish waters compared to freshwater, and the number of statistically significant relationships was considerably higher in freshwater (p < 0.0001). Overall, significant relationships were more commonly reported between FIB and pathogenic bacteria or protozoa, compared to pathogenic viruses (p: 0.0022⁻0.0005), and this was more pronounced in freshwater compared to marine. Statistically significant relationships were typically noted following wet weather events and at sites known to be impacted by recent fecal pollution. Among the studies that reported frequency of detection, FIB were detected most consistently, followed by alternative indicators. MST markers and the three pathogen groups were detected least frequently. This trend was mirrored by reported concentrations for each group of organisms (FIB > alternative indicators > MST markers > pathogens). Thus, while FIB, alternative indicators, and MST markers continue to be suitable indicators of fecal pollution, their relationship with waterborne pathogens, particularly viruses, is tenuous at best and influenced by many different factors such as frequency of detection, variable shedding rates, differential fate and transport characteristics, as well as a broad range of site-specific factors such as the potential for the presence of a complex mixture of multiple sources of fecal contamination and pathogens.
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Affiliation(s)
- Asja Korajkic
- National Exposure Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, OH 45268, USA.
| | - Brian R McMinn
- National Exposure Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, OH 45268, USA.
| | - Valerie J Harwood
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, SCA 110, Tampa, FL 33620, USA.
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Stocker MD, Penrose M, Pachepsky YA. Spatial Patterns of Escherichia coli Concentrations in Sediment before and after High-Flow Events in a First-Order Creek. JOURNAL OF ENVIRONMENTAL QUALITY 2018; 47:958-966. [PMID: 30272771 DOI: 10.2134/jeq2017.11.0451] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Understanding spatial patterns of in freshwater sediments is necessary to characterize sediments as microbial reservoirs and to evaluate the impact of sediment resuspension on microbial water quality in watersheds. Sediment particle size distributions and streambed concentrations were measured along a 500-m-long reach of a first-order creek 1 d before and on Days 1, 3, 6, and 10 after each of two artificial high-flow events, with natural high-flow events also occurring within the sampling periods. Spatial variability of was greater in sediments than in water within any given sampling; however, variation between sampling days was greater for water than for sediment. The mean relative difference analysis revealed temporally stable patterns of concentrations in sediments. rich locations along the reach corresponded to areas with higher organic matter and fine particle contents. Although low ( < 0.5 d) or negative survival rates were observed at most locations along the reach during times where no precipitation was recorded, a small number of locations showed such large concentration increase that on average the survival rate remained positive at the reach scale. The studied creek appears to have hot spots of concentration increase, where conditions for populations to increase are much more favorable than in most other locations across the reach. The effect of this increase can be seen at the reach scale but is difficult to discern without individual sampling that is dense in space and time.
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14
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Pachepsky YA, Allende A, Boithias L, Cho K, Jamieson R, Hofstra N, Molina M. Microbial Water Quality: Monitoring and Modeling. JOURNAL OF ENVIRONMENTAL QUALITY 2018; 47:931-938. [PMID: 30272779 DOI: 10.2134/jeq2018.07.0277] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Microbial water quality lies in the nexus of human, animal, and environmental health. Multidisciplinary efforts are under way to understand how microbial water quality can be monitored, predicted, and managed. This special collection of papers in the was inspired by the idea of creating a special section containing the panoramic view of advances and challenges in the arena of microbial water quality research. It addresses various facets of health-related microorganism release, transport, and survival in the environment. The papers analyze the spatiotemporal variability of microbial water quality, selection of predictors of the spatiotemporal variations, the role of bottom sediments and biofilms, correlations between concentrations of indicator and pathogenic organisms and the role for risk assessment techniques, use of molecular markers, subsurface microbial transport as related to microbial water quality, antibiotic resistance, real-time monitoring and nowcasting, watershed scale modeling, and monitoring design. Both authors and editors represent international experience in the field. The findings underscore the challenges of observing and understanding microbial water quality; they also suggest promising research directions for improving the knowledge base needed to protect and improve our water sources.
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15
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Xue J, Feng Y. Determination of adsorption and desorption of DNA molecules on freshwater and marine sediments. J Appl Microbiol 2018; 124:1480-1492. [DOI: 10.1111/jam.13739] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 01/30/2018] [Accepted: 02/15/2018] [Indexed: 01/30/2023]
Affiliation(s)
- J. Xue
- Department of Crop, Soil and Environmental Sciences; Auburn University; Auburn AL USA
| | - Y. Feng
- Department of Crop, Soil and Environmental Sciences; Auburn University; Auburn AL USA
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16
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Hong EM, Park Y, Muirhead R, Jeong J, Pachepsky YA. Development and evaluation of the bacterial fate and transport module for the Agricultural Policy/Environmental eXtender (APEX) model. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 615:47-58. [PMID: 28963896 DOI: 10.1016/j.scitotenv.2017.09.231] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 09/16/2017] [Accepted: 09/21/2017] [Indexed: 06/07/2023]
Abstract
The Agricultural Policy/Environmental eXtender (APEX) is a watershed-scale water quality model that includes detailed representation of agricultural management. The objective of this work was to develop a process-based model for simulating the fate and transport of manure-borne bacteria on land and in streams with the APEX model. The bacteria model utilizes manure erosion rates to estimate the amount of edge-of-field bacteria export. Bacteria survival in manure is simulated as a two-stage process separately for each manure application event. In-stream microbial fate and transport processes include bacteria release from streambeds due to sediment resuspension during high flow events, active release from the streambed sediment during low flow periods, bacteria settling with sediment, and survival. Default parameter values were selected from published databases and evaluated based on field observations. The APEX model with the newly developed microbial fate and transport module was applied to simulate fate and transport of the fecal indicator bacterium Escherichia coli in the Toenepi watershed, New Zealand that was monitored for seven years. The stream network of the watershed ran through grazing lands with daily bovine waste deposition. Results show that the APEX with the bacteria module reproduced well the monitored pattern of E. coli concentrations at the watershed outlet. The APEX with the microbial fate and transport module will be utilized for predicting microbial quality of water as affected by various agricultural practices, evaluating monitoring protocols, and supporting the selection of management practices based on regulations that rely on fecal indicator bacteria concentrations.
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Affiliation(s)
- Eun-Mi Hong
- USDA-ARS, Environmental Microbial and Food Safety Lab, 10300 Baltimore Avenue, BARC-East Bldg. 173, Beltsville, MD 20705, USA; Oak Ridge Institute of Science and Engineering, ARS Research Participation Program, MS 36 P.O. Box 117, Oak Ridge, TN 37831, USA
| | - Yongeun Park
- USDA-ARS, Environmental Microbial and Food Safety Lab, 10300 Baltimore Avenue, BARC-East Bldg. 173, Beltsville, MD 20705, USA; School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, Republic of Korea
| | - Richard Muirhead
- Farm Systems & Environment, AgResearch Ltd, Invermay Research Centre, Private Bag 50034, Mosgiel 9053, New Zealand
| | - Jaehak Jeong
- Texas A&M AgriLife Research, Temple, TX 76502, USA
| | - Yakov A Pachepsky
- USDA-ARS, Environmental Microbial and Food Safety Lab, 10300 Baltimore Avenue, BARC-East Bldg. 173, Beltsville, MD 20705, USA.
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17
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Porter KDH, Reaney SM, Quilliam RS, Burgess C, Oliver DM. Predicting diffuse microbial pollution risk across catchments: The performance of SCIMAP and recommendations for future development. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 609:456-465. [PMID: 28755595 DOI: 10.1016/j.scitotenv.2017.07.186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 07/20/2017] [Accepted: 07/21/2017] [Indexed: 06/07/2023]
Abstract
Microbial pollution of surface waters in agricultural catchments can be a consequence of poor farm management practices, such as excessive stocking of livestock on vulnerable land or inappropriate handling of manures and slurries. Catchment interventions such as fencing of watercourses, streamside buffer strips and constructed wetlands have the potential to reduce faecal pollution of watercourses. However these interventions are expensive and occupy valuable productive land. There is, therefore, a requirement for tools to assist in the spatial targeting of such interventions to areas where they will have the biggest impact on water quality improvements whist occupying the minimal amount of productive land. SCIMAP is a risk-based model that has been developed for this purpose but with a focus on diffuse sediment and nutrient pollution. In this study we investigated the performance of SCIMAP in predicting microbial pollution of watercourses and assessed modelled outputs of E. coli, a common faecal indicator organism (FIO), against observed water quality information. SCIMAP was applied to two river catchments in the UK. SCIMAP uses land cover risk weightings, which are routed through the landscape based on hydrological connectivity to generate catchment scale maps of relative in-stream pollution risk. Assessment of the model's performance and derivation of optimum land cover risk weightings was achieved using a Monte-Carlo sampling approach. Performance of the SCIMAP framework for informing on FIO risk was variable with better performance in the Yealm catchment (rs=0.88; p<0.01) than the Wyre (rs=-0.36; p>0.05). Across both catchments much uncertainty was associated with the application of optimum risk weightings attributed to different land use classes. Overall, SCIMAP showed potential as a useful tool in the spatial targeting of FIO diffuse pollution management strategies; however, improvements are required to transition the existing SCIMAP framework to a robust FIO risk-mapping tool.
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Affiliation(s)
- Kenneth D H Porter
- Biological & Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK.
| | - Sim M Reaney
- Department of Geography, Durham University, Durham DH1 3LE, UK
| | - Richard S Quilliam
- Biological & Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK
| | - Chris Burgess
- Environment Agency, King's Meadow House, King's Meadow Rd, Reading RG1 8DQ, UK
| | - David M Oliver
- Biological & Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK
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Gregory LF, Karthikeyan R, Aitkenhead-Peterson JA, Gentry TJ, Wagner KL, Harmel RD. Nutrient loading impacts on culturable E. coli and other heterotrophic bacteria fate in simulated stream mesocosms. WATER RESEARCH 2017; 126:442-449. [PMID: 28992591 DOI: 10.1016/j.watres.2017.09.043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 09/06/2017] [Accepted: 09/22/2017] [Indexed: 06/07/2023]
Abstract
Understanding fecal indicator bacteria persistence in aquatic environments is important when making management decisions to improve instream water quality. Routinely, bacteria fate and transport models that rely on published kinetic decay constants are used to inform such decision making but may not adequately represent instream conditions. The objective of this work was to evaluate bacterial responses to applied nutrient amendments and provide additional information regarding bacterial response to applied changes that can be incorporated into future modeling efforts. Re-created stream mesocosms were established in laboratory-based, repurposed algae raceways filled with water and sediment from a small, 3rd order Southeast Texas stream. Mesocosm treatments consisted of low (10x) or high (50x) nutrient doses above ambient water concentrations operated at low (0.032 m/s) or high (0.141 m/s) flow rates. Escherichia coli and heterotrophic bacterial concentrations were quantified in water and sediment over 22 days. No significant differences in kinetic constants were observed among E. coli in water or sediment, and only E. coli in sediment showed any growth response. Heterotrophic plate counts revealed a pronounced growth response in water and sediment within 24 h of nutrient addition but did not differ significantly from control mesocosms. Significant kinetic constant differences between E. coli and heterotrophic bacteria in water were identified (p < 0.01) but did not differ significantly in sediment (p > 0.48). Results indicate that nutrient addition does affect microbial numbers instream, but competition from heterotrophic bacteria may prevent an E. coli growth response.
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Affiliation(s)
- L F Gregory
- Texas Water Resources Institute, Texas A&M AgriLife Research, 2260 TAMU, College Station, TX 77843-2260, USA.
| | - R Karthikeyan
- Department of Biological and Agricultural Engineering, Texas A&M University, 2117 TAMU, College Station, TX 77843-2117, USA
| | - J A Aitkenhead-Peterson
- Department of Soil and Crop Sciences, Texas A&M University, 2474 TAMU, College Station, TX 77843-2474, USA
| | - T J Gentry
- Department of Soil and Crop Sciences, Texas A&M University, 2474 TAMU, College Station, TX 77843-2474, USA
| | - K L Wagner
- Oklahoma Water Resources Center, Oklahoma State University, 139 Ag Hall, Stillwater, OK 74078, USA
| | - R D Harmel
- Center for Agricultural Resources Research, ARS-USDA, 2150 Centre Avenue, Fort Collins, CO 80526-8119, USA
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19
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Hassard F, Andrews A, Jones DL, Parsons L, Jones V, Cox BA, Daldorph P, Brett H, McDonald JE, Malham SK. Physicochemical Factors Influence the Abundance and Culturability of Human Enteric Pathogens and Fecal Indicator Organisms in Estuarine Water and Sediment. Front Microbiol 2017; 8:1996. [PMID: 29089931 PMCID: PMC5650961 DOI: 10.3389/fmicb.2017.01996] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 09/28/2017] [Indexed: 02/06/2023] Open
Abstract
To assess fecal pollution in coastal waters, current monitoring is reliant on culture-based enumeration of bacterial indicators, which does not account for the presence of viable but non-culturable or sediment-associated micro-organisms, preventing effective quantitative microbial risk assessment (QMRA). Seasonal variability in viable but non-culturable or sediment-associated bacteria challenge the use of fecal indicator organisms (FIOs) for water monitoring. We evaluated seasonal changes in FIOs and human enteric pathogen abundance in water and sediments from the Ribble and Conwy estuaries in the UK. Sediments possessed greater bacterial abundance than the overlying water column, however, key pathogenic species (Shigella spp., Campylobacter jejuni, Salmonella spp., hepatitis A virus, hepatitis E virus and norovirus GI and GII) were not detected in sediments. Salmonella was detected in low levels in the Conwy water in spring/summer and norovirus GII was detected in the Ribble water in winter. The abundance of E. coli and Enterococcus spp. quantified by culture-based methods, rarely matched the abundance of these species when measured by qPCR. The discrepancy between these methods was greatest in winter at both estuaries, due to low CFU's, coupled with higher gene copies (GC). Temperature accounted for 60% the variability in bacterial abundance in water in autumn, whilst in winter salinity explained 15% of the variance. Relationships between bacterial indicators/pathogens and physicochemical variables were inconsistent in sediments, no single indicator adequately described occurrence of all bacterial indicators/pathogens. However, important variables included grain size, porosity, clay content and concentrations of Zn, K, and Al. Sediments with greater organic matter content and lower porosity harbored a greater proportion of non-culturable bacteria (including dead cells and extracellular DNA) in winter. Here, we show the link between physicochemical variables and season which govern culturability of human enteric pathogens and FIOs. Therefore, knowledge of these factors is critical for accurate microbial risk assessment. Future water quality management strategies could be improved through monitoring sediment-associated bacteria and non-culturable bacteria. This could facilitate source apportionment of human enteric pathogens and FIOs and direct remedial action to improve water quality.
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Affiliation(s)
- Francis Hassard
- School of Ocean Sciences, Bangor University, Bangor, United Kingdom.,Cranfield Water Science Institute, Cranfield University, Bedford, United Kingdom
| | | | - Davey L Jones
- School of Environment, Natural Resources and Geography, Bangor University, Bangor, United Kingdom
| | - Louise Parsons
- School of Ocean Sciences, Bangor University, Bangor, United Kingdom
| | | | | | | | | | - James E McDonald
- School of Biological Sciences, Bangor University, Bangor, United Kingdom
| | - Shelagh K Malham
- School of Ocean Sciences, Bangor University, Bangor, United Kingdom
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20
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Donahue A, Feng Z, Kelly E, Reniers A, Solo-Gabriele HM. Significance of beach geomorphology on fecal indicator bacteria levels. MARINE POLLUTION BULLETIN 2017; 121:160-167. [PMID: 28595980 PMCID: PMC5548550 DOI: 10.1016/j.marpolbul.2017.05.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 04/29/2017] [Accepted: 05/10/2017] [Indexed: 05/28/2023]
Abstract
Large databases of fecal indicator bacteria (FIB) measurements are available for coastal waters. With the assistance of satellite imagery, we illustrated the power of assessing data for many sites by evaluating beach features such as geomorphology, distance from rivers and canals, presence of piers and causeways, and degree of urbanization coupled with the enterococci FIB database for the state of Florida. We found that beach geomorphology was the primary characteristic associated with enterococci levels that exceeded regulatory guidelines. Beaches in close proximity to marshes or within bays had higher enterococci exceedances in comparison to open coast beaches. For open coast beaches, greater enterococci exceedances were associated with nearby rivers and higher levels of urbanization. Piers and causeways had a minimal contribution, as their effect was often overwhelmed by beach geomorphology. Results can be used to understand the potential causes of elevated enterococci levels and to promote public health.
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Affiliation(s)
- Allison Donahue
- Department of Biology, University of Miami, Coral Gables, FL, USA; Center for Oceans and Human Health, Rosenstiel School for Marine and Atmospheric Science, Key Biscayne, FL, USA; Department of Civil, Architectural, and Environmental Engineering, Coral Gables, FL, USA
| | - Zhixuan Feng
- Center for Oceans and Human Health, Rosenstiel School for Marine and Atmospheric Science, Key Biscayne, FL, USA; Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Elizabeth Kelly
- Center for Oceans and Human Health, Rosenstiel School for Marine and Atmospheric Science, Key Biscayne, FL, USA; Department of Civil, Architectural, and Environmental Engineering, Coral Gables, FL, USA; Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, FL, USA
| | - Ad Reniers
- Center for Oceans and Human Health, Rosenstiel School for Marine and Atmospheric Science, Key Biscayne, FL, USA; Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft 2628CN, The Netherlands
| | - Helena M Solo-Gabriele
- Center for Oceans and Human Health, Rosenstiel School for Marine and Atmospheric Science, Key Biscayne, FL, USA; Department of Civil, Architectural, and Environmental Engineering, Coral Gables, FL, USA; Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, FL, USA.
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21
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Zimmer-Faust AG, Thulsiraj V, Marambio-Jones C, Cao Y, Griffith JF, Holden PA, Jay JA. Effect of freshwater sediment characteristics on the persistence of fecal indicator bacteria and genetic markers within a Southern California watershed. WATER RESEARCH 2017; 119:1-11. [PMID: 28433878 DOI: 10.1016/j.watres.2017.04.028] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 03/22/2017] [Accepted: 04/09/2017] [Indexed: 06/07/2023]
Abstract
In this study, the aging of culturable FIB and DNA representing genetic markers for Enterococcus spp. (ENT1A), general Bacteroides (GB3), and human-associated Bacteroides (HF183) in freshwater sediments was evaluated. Freshwater sediment was collected from four different sites within the upper and lower reach of the Topanga Creek Watershed and two additional comparator sites within the Santa Monica Bay, for a total of six sites. Untreated (ambient) and oven-dried (reduced microbiota) sediment was inoculated with 5% sewage and artificial freshwater. Microcosms were held for a 21-day period and sampled on day 0, 1, 3, 5, 7, 12, and 21. There were substantial differences in decay among the sediments tested, and decay rates were related to sediment characteristics. In the ambient sediments, smaller particle size and higher levels of organic matter and nutrients (nitrogen and phosphorus) were associated with increased persistence of the GB3 marker and culturable Escherichia coli (cEC) and enterococci (cENT). The HF183 marker exhibited decay rates of -0.50 to -0.96 day-1, which was 2-5 times faster in certain ambient sediments than decay of culturable FIB and the ENT1A and GB3 markers. The ENT1A and GB3 markers decayed at rates of between -0.07 and -0.28 and -0.10 to -0.44 day-1, and cEC and cENT decayed at rates of between -0.22 and -0.81 and -0.03 and -0.40 day-1, respectively. In the oven-dried sediments, increased persistence of all indicators and potential for limited growth of culturable FIB and the GB3 and ENT1A markers was observed. A simplified two-box model using the HF183 marker and cENT decay rates generated from the microcosm experiments was applied to two reaches within the Topanga Canyon watershed in order to provide context for the variability in decay rates observed. The model predicted lower ambient concentrations of enterococci in sediment in the upper (90 MPN g-1) versus lower Topanga watershed (530 MPN g-1) and low ambient levels of the HF183 marker (below the LLOQ) in sediments in both lower and upper watersheds. It is important to consider the variability in the persistence of genetic markers and FIB when evaluating indicators of fecal contamination in sediments, even within one watershed.
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Affiliation(s)
- Amity G Zimmer-Faust
- Department of Civil and Environmental Engineering, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Vanessa Thulsiraj
- Department of Civil and Environmental Engineering, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Catalina Marambio-Jones
- Department of Civil and Environmental Engineering, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Yiping Cao
- Southern California Coastal Water Research Project, 3535 Harbor Blvd Ste 110, Costa Mesa, CA 92626, United States
| | - John F Griffith
- Southern California Coastal Water Research Project, 3535 Harbor Blvd Ste 110, Costa Mesa, CA 92626, United States
| | - Patricia A Holden
- Earth Research Institute and Bren School of Environmental Science & Management, University of California, Santa Barbara, CA 93106, United States
| | - Jennifer A Jay
- Department of Civil and Environmental Engineering, University of California at Los Angeles, Los Angeles, CA 90095, United States.
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Abia ALK, James C, Ubomba-Jaswa E, Benteke Momba MN. Microbial Remobilisation on Riverbed Sediment Disturbance in Experimental Flumes and a Human-Impacted River: Implication for Water Resource Management and Public Health in Developing Sub-Saharan African Countries. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2017; 14:E306. [PMID: 28295001 PMCID: PMC5369142 DOI: 10.3390/ijerph14030306] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 03/09/2017] [Accepted: 03/10/2017] [Indexed: 11/29/2022]
Abstract
Resuspension of sediment-borne microorganisms (including pathogens) into the water column could increase the health risk for those using river water for different purposes. In the present work, we (1) investigated the effect of sediment disturbance on microbial resuspension from riverbed sediments in laboratory flow-chambers and in the Apies River, Gauteng, South Africa; and (2) estimated flow conditions for sediment-borne microorganism entrainment/resuspension in the river. For mechanical disturbance, the top 2 cm of the sediment in flow-chambers was manually stirred. Simulating sudden discharge into the river, water (3 L) was poured within 30 s into the chambers at a 45° angle to the chamber width. In the field, sediment was disturbed by raking the riverbed and by cows crossing in the river. Water samples before and after sediment disturbance were analysed for Escherichia coli. Sediment disturbance caused an increase in water E. coli counts by up to 7.9-35.8 times original values. Using Shields criterion, river-flow of 0.15-0.69 m³/s could cause bed particle entrainment; while ~1.57-7.23 m³/s would cause resuspension. Thus, sediment disturbance in the Apies River would resuspend E. coli (and pathogens), with possible negative health implications for communities using such water. Therefore, monitoring surface water bodies should include microbial sediment quality.
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Affiliation(s)
- Akebe Luther King Abia
- Departments of Biotechnology, Vaal university of Technology, Private Bag X021, Andries Potgieter Blvd, Vanderbijlpark 1911, South Africa.
| | - Chris James
- School of Civil & Environmental Engineering, University of the Witwatersrand, Johannesburg 2050, South Africa.
| | - Eunice Ubomba-Jaswa
- Natural Resources and the Environment, CSIR, P.O. Box 395, Pretoria 0001, South Africa.
| | - Maggy Ndombo Benteke Momba
- Department of Environmental, Water and Earth Science, Tshwane University of Technology, Arcadia Campus, 175 Nelson Mandela Drive, Pretoria 0001, South Africa.
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Pachepsky Y, Stocker M, Saldaña MO, Shelton D. Enrichment of stream water with fecal indicator organisms during baseflow periods. ENVIRONMENTAL MONITORING AND ASSESSMENT 2017; 189:51. [PMID: 28063117 DOI: 10.1007/s10661-016-5763-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 12/27/2016] [Indexed: 06/06/2023]
Abstract
Fecal indicator organisms (FIOs) are generally believed to be present in surface waters due solely to direct deposition of feces or through transport in runoff. However, emerging evidence points toward hyporheic exchange between sediment pore water and the overlying water column during baseflow periods as a source of FIOs is surface waters. The objective of this work was to (a) propose a mass balance-based technique for estimating changes of FIO concentrations in the same volume of water (or "slug") from the inlet to outlet of stream reaches in baseflow conditions and (b) to use such enumeration to estimate rate of the FIO release to stream water column. Concentrations of Escherichia coli (E. coli) and enterococci were measured in the slug while simultaneously monitoring the movement of a conservative tracer, Br that labeled the slug. Concentrations of E. coli in the slug were significantly larger (P = 0.035, P = 0.001, and P = 0.001, respectively) at the outlet reach in all three replications, while enterococci concentrations were significantly larger in two of three replications (P = 0.001, P < 0.001, and P = 0.602). When estimated without accounting for die-off in water column, FIO net release rates across replications ranged from 36 to 57 cells m-2 s-1 and 43 to 87 cells m-2 s-1 for E. coli and enterococci, respectively. These release rates were 5 to 20% higher when the die-off in water column was taken into account. No diurnal trends were observed in indicator concentrations. No FIO sources other than bottom sediment have been observed during the baseflow period. FIOs are released into stream water column through hyporheic exchange during baseflow periods.
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Affiliation(s)
- Yakov Pachepsky
- USDA-ARS Environmental Microbial and Food Safety Laboratory, Beltsville, MD, USA.
| | - Matthew Stocker
- USDA-ARS Environmental Microbial and Food Safety Laboratory, Beltsville, MD, USA
- Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN, USA
| | - Manuel Olmeda Saldaña
- Department of Environmental Sciences, University of Puerto Rico - Rio Piedras, San Juan, Puerto Rico
| | - Daniel Shelton
- USDA-ARS Environmental Microbial and Food Safety Laboratory, Beltsville, MD, USA
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Hassard F, Gwyther CL, Farkas K, Andrews A, Jones V, Cox B, Brett H, Jones DL, McDonald JE, Malham SK. Abundance and Distribution of Enteric Bacteria and Viruses in Coastal and Estuarine Sediments-a Review. Front Microbiol 2016; 7:1692. [PMID: 27847499 PMCID: PMC5088438 DOI: 10.3389/fmicb.2016.01692] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 10/10/2016] [Indexed: 11/26/2022] Open
Abstract
The long term survival of fecal indicator organisms (FIOs) and human pathogenic microorganisms in sediments is important from a water quality, human health and ecological perspective. Typically, both bacteria and viruses strongly associate with particulate matter present in freshwater, estuarine and marine environments. This association tends to be stronger in finer textured sediments and is strongly influenced by the type and quantity of clay minerals and organic matter present. Binding to particle surfaces promotes the persistence of bacteria in the environment by offering physical and chemical protection from biotic and abiotic stresses. How bacterial and viral viability and pathogenicity is influenced by surface attachment requires further study. Typically, long-term association with surfaces including sediments induces bacteria to enter a viable-but-non-culturable (VBNC) state. Inherent methodological challenges of quantifying VBNC bacteria may lead to the frequent under-reporting of their abundance in sediments. The implications of this in a quantitative risk assessment context remain unclear. Similarly, sediments can harbor significant amounts of enteric viruses, however, the factors regulating their persistence remains poorly understood. Quantification of viruses in sediment remains problematic due to our poor ability to recover intact viral particles from sediment surfaces (typically <10%), our inability to distinguish between infective and damaged (non-infective) viral particles, aggregation of viral particles, and inhibition during qPCR. This suggests that the true viral titre in sediments may be being vastly underestimated. In turn, this is limiting our ability to understand the fate and transport of viruses in sediments. Model systems (e.g., human cell culture) are also lacking for some key viruses, preventing our ability to evaluate the infectivity of viruses recovered from sediments (e.g., norovirus). The release of particle-bound bacteria and viruses into the water column during sediment resuspension also represents a risk to water quality. In conclusion, our poor process level understanding of viral/bacterial-sediment interactions combined with methodological challenges is limiting the accurate source apportionment and quantitative microbial risk assessment for pathogenic organisms associated with sediments in aquatic environments.
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Affiliation(s)
| | - Ceri L. Gwyther
- Department of Engineering and Innovation, Open UniversityMilton Keynes, UK
| | - Kata Farkas
- School of Environment, Natural Resources and Geography, Bangor UniversityBangor, UK
| | | | | | | | | | - Davey L. Jones
- School of Environment, Natural Resources and Geography, Bangor UniversityBangor, UK
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Cho KH, Pachepsky YA, Oliver DM, Muirhead RW, Park Y, Quilliam RS, Shelton DR. Modeling fate and transport of fecally-derived microorganisms at the watershed scale: State of the science and future opportunities. WATER RESEARCH 2016; 100:38-56. [PMID: 27176652 DOI: 10.1016/j.watres.2016.04.064] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 04/27/2016] [Accepted: 04/28/2016] [Indexed: 06/05/2023]
Abstract
Natural waters serve as habitat for a wide range of microorganisms, a proportion of which may be derived from fecal material. A number of watershed models have been developed to understand and predict the fate and transport of fecal microorganisms within complex watersheds, as well as to determine whether microbial water quality standards can be satisfied under site-specific meteorological and/or management conditions. The aim of this review is to highlight and critically evaluate developments in the modeling of microbial water quality of surface waters over the last 10 years and to discuss the future of model development and application at the watershed scale, with a particular focus on fecal indicator organisms (FIOs). In doing so, an agenda of research opportunities is identified to help deliver improvements in the modeling of microbial water quality draining through complex landscape systems. This comprehensive review therefore provides a timely steer to help strengthen future modeling capability of FIOs in surface water environments and provides a useful resource to complement the development of risk management strategies to reduce microbial impairment of freshwater sources.
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Affiliation(s)
- Kyung Hwa Cho
- School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Ulsan, 689-798, South Korea
| | - Yakov A Pachepsky
- USDA-ARS, Environmental Microbial and Food Safety Laboratory, 10300 Baltimore Ave. Building 173, BARC-EAST, Beltsville, MD 20705, USA
| | - David M Oliver
- Biological & Environmental Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Richard W Muirhead
- Land & Environment, AgResearch Ltd, Invermay Research Centre, Private Bag 50034, Mosgiel 9053, New Zealand
| | - Yongeun Park
- USDA-ARS, Environmental Microbial and Food Safety Laboratory, 10300 Baltimore Ave. Building 173, BARC-EAST, Beltsville, MD 20705, USA
| | - Richard S Quilliam
- Biological & Environmental Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Daniel R Shelton
- USDA-ARS, Environmental Microbial and Food Safety Laboratory, 10300 Baltimore Ave. Building 173, BARC-EAST, Beltsville, MD 20705, USA
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Jalliffier-Verne I, Heniche M, Madoux-Humery AS, Galarneau M, Servais P, Prévost M, Dorner S. Cumulative effects of fecal contamination from combined sewer overflows: Management for source water protection. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2016; 174:62-70. [PMID: 27011341 DOI: 10.1016/j.jenvman.2016.03.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 02/26/2016] [Accepted: 03/01/2016] [Indexed: 05/06/2023]
Abstract
The quality of a drinking water source depends largely on upstream contaminant discharges. Sewer overflows can have a large influence on downstream drinking water intakes as they discharge untreated or partially treated wastewaters that may be contaminated with pathogens. This study focuses on the quantification of Escherichia coli discharges from combined sewer overflows (CSOs) and the dispersion and diffusion in receiving waters in order to prioritize actions for source water protection. E. coli concentrations from CSOs were estimated from monitoring data at a series of overflow structures and then applied to the 42 active overflow structures between 2009 and 2012 using a simple relationship based upon the population within the drainage network. From these estimates, a transport-dispersion model was calibrated with data from a monitoring program from both overflow structures and downstream drinking water intakes. The model was validated with 15 extreme events such as a large number of overflows (n > 8) or high concentrations at drinking water intakes. Model results demonstrated the importance of the cumulative effects of CSOs on the degradation of water quality downstream. However, permits are typically issued on a discharge point basis and do not consider cumulative effects. Source water protection plans must consider the cumulative effects of discharges and their concentrations because the simultaneous discharge of multiple overflows can lead to elevated E. coli concentrations at a drinking water intake. In addition, some CSOs have a disproportionate impact on peak concentrations at drinking water intakes. As such, it is recommended that the management of CSOs move away from frequency based permitting at the discharge point to focus on the development of comprehensive strategies to reduce cumulative and peak discharges from CSOs upstream of drinking water intakes.
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Affiliation(s)
- Isabelle Jalliffier-Verne
- Department of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, 2900, boul. Édouard-Montpetit, Montréal, QC, H3T 1J4, Canada.
| | - Mourad Heniche
- Department of Chemical Engineering, École Polytechnique de Montréal, 2900, boul. Édouard-Montpetit, Montréal, QC, H3T 1J4, Canada.
| | - Anne-Sophie Madoux-Humery
- Department of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, 2900, boul. Édouard-Montpetit, Montréal, QC, H3T 1J4, Canada.
| | - Martine Galarneau
- Engineering Department, City of Laval, 1333, boulevard Chomedey, Rez-de-chaussée, C.P. 422 Succ. Saint-Martin, Laval, QC, H7V 3Z4, Canada.
| | - Pierre Servais
- Écologie des Systèmes Aquatiques, Université Libre de Bruxelles, Campus Plaine, CP 221, 1050, Brussels, Belgium.
| | - Michèle Prévost
- Department of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, 2900, boul. Édouard-Montpetit, Montréal, QC, H3T 1J4, Canada.
| | - Sarah Dorner
- Department of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, 2900, boul. Édouard-Montpetit, Montréal, QC, H3T 1J4, Canada.
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Chandrasekaran R, Hamilton MJ, Wang P, Staley C, Matteson S, Birr A, Sadowsky MJ. Geographic isolation of Escherichia coli genotypes in sediments and water of the Seven Mile Creek - A constructed riverine watershed. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 538:78-85. [PMID: 26298250 DOI: 10.1016/j.scitotenv.2015.08.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/03/2015] [Accepted: 08/04/2015] [Indexed: 06/04/2023]
Abstract
Escherichia coli is used to indicate fecal contamination in freshwater systems and is an indicator of the potential presence of human pathogens. However, naturalized E. coli strains that persist and grow in the environment confound the use of this bacterium as a fecal indicator. Here we examined the spatial and temporal distribution of E. coli in water and sediments of the Seven Mile Creek (SMC), a constructed, ephemeral watershed. E. coli concentrations showed variation by site and date, likely due to changes in temperature and rainfall. Horizontal fluorophore enhanced rep-PCR (HFERP) DNA fingerprint analyses indicated that E. coli populations were very diverse and consisted of transient and naturalized strains, which were especially prevalent in sediment. E. coli fingerprints from water and sediment collected in the same year clustered together with significant overlap, indicating exchange of strains between matrices. Isolates obtained during periods of flow, but not during non-flow conditions, clustered together regardless of sample site, indicating that transport between sites occurred. Naturalized E. coli strains were found in the SMC and strains become geographically isolated and distinct during non-flow conditions. Isolates collected during late spring to fall clustered together at each site, suggesting that temperature and growth of naturalized strains are likely factors affecting population dynamics. Results of this study show that newly introduced and naturalized E. coli strains are present in the SMC. Results of this study highlight an important concern for resource managers using this species for water quality monitoring.
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Affiliation(s)
| | - Matthew J Hamilton
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA; Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN 55108, USA
| | - Ping Wang
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA
| | - Christopher Staley
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA
| | - Scott Matteson
- Water Resource Center, Minnesota State University, Mankato, MN 55108, USA.
| | - Adam Birr
- Minnesota Department of Agriculture, St. Paul, MN 55108, USA.
| | - Michael J Sadowsky
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA; Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN 55108, USA.
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28
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Oliver DM, Porter KDH, Heathwaite AL, Zhang T, Quilliam RS. Impact of low intensity summer rainfall on E. coli-discharge event dynamics with reference to sample acquisition and storage. ENVIRONMENTAL MONITORING AND ASSESSMENT 2015; 187:426. [PMID: 26065889 DOI: 10.1007/s10661-015-4628-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/19/2015] [Indexed: 06/04/2023]
Abstract
Understanding the role of different rainfall scenarios on faecal indicator organism (FIO) dynamics under variable field conditions is important to strengthen the evidence base on which regulators and land managers can base informed decisions regarding diffuse microbial pollution risks. We sought to investigate the impact of low intensity summer rainfall on Escherichia coli-discharge (Q) patterns at the headwater catchment scale in order to provide new empirical data on FIO concentrations observed during baseflow conditions. In addition, we evaluated the potential impact of using automatic samplers to collect and store freshwater samples for subsequent microbial analysis during summer storm sampling campaigns. The temporal variation of E. coli concentrations with Q was captured during six events throughout a relatively dry summer in central Scotland. The relationship between E. coli concentration and Q was complex with no discernible patterns of cell emergence with Q that were repeated across all events. On several occasions, an order of magnitude increase in E. coli concentrations occurred even with slight increases in Q, but responses were not consistent and highlighted the challenges of attempting to characterise temporal responses of E. coli concentrations relative to Q during low intensity rainfall. Cross-comparison of E. coli concentrations determined in water samples using simultaneous manual grab and automated sample collection was undertaken with no difference in concentrations observed between methods. However, the duration of sample storage within the autosampler unit was found to be more problematic in terms of impacting on the representativeness of microbial water quality, with unrefrigerated autosamplers exhibiting significantly different concentrations of E. coli relative to initial samples after 12-h storage. The findings from this study provide important empirical contributions to the growing evidence base in the field of catchment microbial dynamics.
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Affiliation(s)
- David M Oliver
- Division of Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, Scotland, FK9 4LA, UK,
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