Application of microbial source tracking methods in a Gulf of Mexico field setting

Korajkic, Asja; Badgley, Brian D.; Brownell, Miriam; Harwood, Valerie J.

doi:10.1111/j.1365-2672.2009.04351.x

Cited by 39 publications

(30 citation statements)

References 52 publications

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“…They measured fecal coliform rather than E. coli decay rates and found that this group declined more rapidly in marine sediments than in freshwater sediments; however, the differences were not as great as those observed in this study. Our field studies have shown that fecal coliform concentrations are frequently up to 2 orders of magnitude greater than E. coli concentrations in environmental waters, suggesting that some members of the larger group are better survivors in the secondary habitat than most E. coli strains (64)(65)(66)(67).…”

Section: Discussionmentioning

confidence: 99%

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

Korajkic

Wanjugi

Harwood

2013

Appl Environ Microbiol

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The reported fate of Escherichia coli in the environment ranges from extended persistence to rapid decline. Incomplete understanding of factors that influence survival hinders risk assessment and modeling of the fate of fecal indicator bacteria (FIB) and pathogens. FIB persistence in subtropical aquatic environments was explored in outdoor mesocosms inoculated with five E. coli strains. The manipulated environmental factors were (i) presence or absence of indigenous microbiota (attained by natural, disinfected, and cycloheximide treatments), (ii) freshwater versus seawater, and (iii) water column versus sediment matrices. When indigenous microbes were removed (disinfected), E. coli concentrations decreased little despite exposure to sunlight. Conversely, under conditions that included the indigenous microbiota (natural), significantly greater declines in E. coli occurred regardless of the habitat. The presence of indigenous microbiota and matrix significantly influenced E. coli decline, but their relative importance differed in freshwater versus seawater. Cycloheximide, which inhibits protein synthesis in eukaryotes, significantly diminished the magnitude of E. coli decline in water but not in sediments. The inactivation of protozoa and bacterial competitors (disinfected) caused a greater decline in E. coli than cycloheximide alone in water and sediments. These results indicate that the autochthonous microbiota are an important contributor to the decline of E. coli in fresh and seawater subtropical systems, but their relative contribution is habitat dependent. This work advances our understanding of how interactions with autochthonous microbiota influence the fate of E. coli in aquatic environments and provides the framework for studies of the ecology of enteric pathogens and other allochthonous bacteria in similar environments.T he sanitary quality of recreational waters in Florida and across the United States is currently assessed by enumeration of fecal indicator bacteria (FIB) (i.e., fecal coliforms, Escherichia coli, and enterococci), which are also intended to act as pathogen surrogates (1, 2). The validity of this paradigm is the subject of ongoing debate, and it is argued that the current regulatory standards do not adequately protect human health, due mainly to the differences in survival and transport characteristics between the FIB and pathogens (3-9). When the assumed predictive relationship is absent (e.g., FIB not detected but pathogens present), public health may be threatened by exposure of humans to pathogens. On the other hand, FIB that are detected in the absence of pathogens can lead to unnecessary beach and shellfishing area closures, which can pose economic hardships in coastal communities.While the roles of sediments and aquatic vegetation as a refuge and a potential reservoir of FIB are the subjects of many studies (10-16), the relative influence of indigenous microbiota on the persistence and rate of decline of FIB in aquatic environments is less well characterized. Germicidal sunlight r...

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Section: Discussionmentioning

confidence: 99%

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

Korajkic

Wanjugi

Harwood

2013

Appl Environ Microbiol

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“…The occurrence of esp fm was correlated with human polyomaviruses in polluted surface waters in Florida (227) and with fecal coliforms in another study (197). It has also been used in field studies in Florida, the Great Lakes, and Australia (5,39,196,209). A quantitative PCR (qPCR) method for esp fm has been developed and used in field studies in Australia (4).…”

Section: Microbial Source Trackingmentioning

confidence: 99%

Enterococci in the Environment

Byappanahalli

Nevers

Korajkic

et al. 2012

Microbiol Mol Biol Rev

564

383

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SUMMARYEnterococci are common, commensal members of gut communities in mammals and birds, yet they are also opportunistic pathogens that cause millions of human and animal infections annually. Because they are shed in human and animal feces, are readily culturable, and predict human health risks from exposure to polluted recreational waters, they are used as surrogates for waterborne pathogens and as fecal indicator bacteria (FIB) in research and in water quality testing throughout the world. Evidence from several decades of research demonstrates, however, that enterococci may be present in high densities in the absence of obvious fecal sources and that environmental reservoirs of these FIB are important sources and sinks, with the potential to impact water quality. This review focuses on the distribution and microbial ecology of enterococci in environmental (secondary) habitats, including the effect of environmental stressors; an outline of their known and apparent sources, sinks, and fluxes; and an overview of the use of enterococci as FIB. Finally, the significance of emerging methodologies, such as microbial source tracking (MST) and empirical predictive models, as tools in water quality monitoring is addressed. The mounting evidence for widespread extraenteric sources and reservoirs of enterococci demonstrates the versatility of the genusEnterococcusand argues for the necessity of a better understanding of their ecology in natural environments, as well as their roles as opportunistic pathogens and indicators of human pathogens.

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“…Before filtration, sediment samples were weighed and diluted 1:10 (wt/vol) in sterile buffered water (20) and sonicated for 30 s at 14 W (sonic dismembrator model 100; Fisher Scientific) to dislodge bacterial particles attached to the sediment for the direct effect microcosms (1,29). For the indirect effect experiment, sediment samples were shaken for 2 min instead of being subjected to sonication (8).…”

Section: Direct Effect Experimentmentioning

confidence: 99%

Test of Direct and Indirect Effects of Agrochemicals on the Survival of Fecal Indicator Bacteria

Staley

Rohr

Harwood

2011

Appl Environ Microbiol

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Water bodies often receive agrochemicals and animal waste carrying fecal indicator bacteria (FIB) and zoonotic pathogens, but we know little about the effects of agrochemicals on these microbes. We assessed the direct effects of the pesticides atrazine, malathion, and chlorothalonil and inorganic fertilizer on Escherichia coli and enterococcal survival in simplified microcosms held in the dark. E. coli strain composition in sediments and water column were positively correlated, but none of the agrochemicals had significant direct effects on E. coli strain composition or on densities of culturable FIBs. In a companion study, microcosms with nondisinfected pond water and sediments were exposed to or shielded from sunlight to examine the potential indirect effects of atrazine and inorganic fertilizer on E. coli. The herbicide atrazine had no effect on E. coli in dark-exposed microcosms containing natural microbial and algal communities. However, in light-exposed microcosms, atrazine significantly lowered E. coli densities in the water column and significantly increased densities in the sediment compared to controls. This effect appears to be mediated by the effects of atrazine on algae, given that atrazine significantly reduced phytoplankton, which was a positive and negative predictor of E. coli densities in the water column and sediment, respectively. These data suggest that atrazine does not directly affect the survival of FIB, rather that it indirectly alters the distribution and abundance of E. coli by altering phytoplankton and periphyton communities. These results improve our understanding of the influence of agricultural practices on FIB densities in water bodies impacted by agricultural runoff.

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Application of microbial source tracking methods in a Gulf of Mexico field setting

Cited by 39 publications

References 52 publications

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

Enterococci in the Environment

Test of Direct and Indirect Effects of Agrochemicals on the Survival of Fecal Indicator Bacteria

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