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      Detection and occurrence of indicator organisms and pathogens

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          Abstract

          This review paper focuses on detection and quantification techniques of indicator organisms that can be used for water quality assessment. The environmental pathogens that are critical to understand and better evaluate water quality are also discussed in this paper. Several recent studies using culture‐independent methods such as microbial source tracking, pulsed field gel electrophoresis, mitochondrial DNA, and next generation sequencing to assess various environmental samples and water bodies have been reviewed.

          Practitioner points

          • Various waterborne pathogens and cases of outbreak occurances due to presence of pathogens are studied in this review paper.

          • Recent studies for detecting major indicator organisms to evaluate the presence of pathogens in water bodies are reviewed.

          • Culture‐independent techniques as robust tools to detect and quantify waterborne pathogens are discussed in this review paper.

          Abstract

          Characterization of indicator organisms and microbial source tracking are robust tools, which can detect the potential pathogens and contribute to classify microorganisms based on their phenotypic or genotypic fingerprints. Microbial source tracking incorporates genetic sequences (called as markers) unique to specific bacterial or viral species from specific animal hosts, which conveys insight into sources of fecal contamination.

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          Most cited references39

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          Is Open Access

          Next-generation sequencing (NGS) for assessment of microbial water quality: current progress, challenges, and future opportunities

          Water quality is an emergent property of a complex system comprised of interacting microbial populations and introduced microbial and chemical contaminants. Studies leveraging next-generation sequencing (NGS) technologies are providing new insights into the ecology of microbially mediated processes that influence fresh water quality such as algal blooms, contaminant biodegradation, and pathogen dissemination. In addition, sequencing methods targeting small subunit (SSU) rRNA hypervariable regions have allowed identification of signature microbial species that serve as bioindicators for sewage contamination in these environments. Beyond amplicon sequencing, metagenomic and metatranscriptomic analyses of microbial communities in fresh water environments reveal the genetic capabilities and interplay of waterborne microorganisms, shedding light on the mechanisms for production and biodegradation of toxins and other contaminants. This review discusses the challenges and benefits of applying NGS-based methods to water quality research and assessment. We will consider the suitability and biases inherent in the application of NGS as a screening tool for assessment of biological risks and discuss the potential and limitations for direct quantitative interpretation of NGS data. Secondly, we will examine case studies from recent literature where NGS based methods have been applied to topics in water quality assessment, including development of bioindicators for sewage pollution and microbial source tracking, characterizing the distribution of toxin and antibiotic resistance genes in water samples, and investigating mechanisms of biodegradation of harmful pollutants that threaten water quality. Finally, we provide a short review of emerging NGS platforms and their potential applications to the next generation of water quality assessment tools.
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            Identification of nonpoint sources of fecal pollution in coastal waters by using host-specific 16S ribosomal DNA genetic markers from fecal anaerobes.

            We describe a new PCR-based method for distinguishing human and cow fecal contamination in coastal waters without culturing indicator organisms, and we show that the method can be used to track bacterial marker sequences in complex environments. We identified two human-specific genetic markers and five cow-specific genetic markers in fecal samples by amplifying 16S ribosomal DNA (rDNA) fragments from members of the genus Bifidobacterium and the Bacteroides-Prevotella group and performing length heterogeneity PCR and terminal restriction fragment length polymorphism analyses. Host-specific patterns suggested that there are species composition differences in the Bifidobacterium and Bacteroides-Prevotella populations of human and cow feces. The patterns were highly reproducible among different hosts belonging to the same species. Additionally, all host-specific genetic markers were detected in water samples collected from areas frequently contaminated with fecal pollution. Ease of detection and longer survival in water made Bacteroides-Prevotella indicators better than Bifidobacterium indicators. Fecal 16S rDNA sequences corresponding to our Bacteroides-Prevotella markers comprised closely related gene clusters, none of which exactly matched previously published Bacteroides or Prevotella sequences. Our method detected host-specific markers in water at pollutant concentrations of 2.8 x 10(-5) to 2.8 x 10(-7) g (dry weight) of feces/liter and 6.8 x 10(-7) g (dry weight) of sewage/liter. Although our aim was to identify nonpoint sources of fecal contamination, the method described here should be widely applicable for monitoring spatial and temporal fluctuations in specific bacterial groups in natural environments.
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              Discovering new indicators of fecal pollution.

              Fecal pollution indicators are essential to identify and remediate contamination sources and protect public health. Historically, easily cultured facultative anaerobes such as fecal coliforms, Escherichia coli, or enterococci have been used but these indicators generally provide no information as to their source. More recently, molecular methods have targeted fecal anaerobes, which are much more abundant in humans and other mammals, and some strains appear to be associated with particular host sources. Next-generation sequencing and microbiome studies have created an unprecedented inventory of microbial communities associated with fecal sources, allowing reexamination of which taxonomic groups are best suited as informative indicators. The use of new computational methods, such as oligotyping coupled with well-established machine learning approaches, is providing new insights into patterns of host association. In this review we examine the basis for host-specificity and the rationale for using 16S rRNA gene targets for alternative indicators and highlight two taxonomic groups, Bacteroidales and Lachnospiraceae, which are rich in host-specific bacterial organisms. Finally, we discuss considerations for using alternative indicators for water quality assessments with a particular focus on detecting human sewage sources of contamination.
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                Author and article information

                Contributors
                motlagh@csus.edu
                Journal
                Water Environ Res
                Water Environ. Res
                10.1002/(ISSN)1554-7531
                WER
                Water Environment Research
                John Wiley and Sons Inc. (Hoboken )
                1061-4303
                1554-7531
                21 September 2019
                October 2019
                : 91
                : 10 ( doiID: 10.1002/wer.v91.10 )
                : 1402-1408
                Affiliations
                [ 1 ] Department of Civil Engineering California State University Sacramento California
                Author notes
                [*] [* ] Correspondence to: Amir M. Motlagh, Department of Civil Engineering, California State University, Sacramento, CA.

                Email: motlagh@ 123456csus.edu

                [*]

                WEF Member/Fellow

                Author information
                https://orcid.org/0000-0002-2039-0291
                Article
                WER1238
                10.1002/wer.1238
                7169830
                31505073
                365c9925-4043-4eaa-b546-4b4fa6ff67b7
                © 2019 Water Environment Federation

                This article is being made freely available through PubMed Central as part of the COVID-19 public health emergency response. It can be used for unrestricted research re-use and analysis in any form or by any means with acknowledgement of the original source, for the duration of the public health emergency.

                History
                : 30 May 2019
                : 03 September 2019
                : 04 September 2019
                Page count
                Figures: 0, Tables: 0, Pages: 7, Words: 6231
                Categories
                Annual Literature Review
                Annual Literature Review
                Custom metadata
                2.0
                October 2019
                Converter:WILEY_ML3GV2_TO_JATSPMC version:5.8.0 mode:remove_FC converted:15.04.2020

                environmental health,indicator organisms,microbial source tracking,outbreak,pathogen

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