Isolation of fecal coliforms from pristine sites in a tropical rain forest

Mechanisms Governing Metabolic Heterogeneity in Breast Cancer and Other Tumors

Reprogramming of metabolic priorities promotes tumor progression. Our understanding of the Warburg effect, based on studies of cultured cancer cells, has evolved to a more complex understanding of tumor metabolism within an ecosystem that provides and catabolizes diverse nutrients provided by the local tumor microenvironment. Recent studies have illustrated that heterogeneous metabolic changes occur at the level of tumor type, tumor subtype, within the tumor itself, and within the tumor microenvironment. Thus, altered metabolism occurs in cancer cells and in the tumor microenvironment (fibroblasts, immune cells and fat cells). Herein we describe how these growth advantages are obtained through either “convergent” genetic changes, in which common metabolic properties are induced as a final common pathway induced by diverse oncogene factors, or “divergent” genetic changes, in which distinct factors lead to subtype-selective phenotypes and thereby tumor heterogeneity. Metabolic heterogeneity allows subtyping of cancers and further metabolic heterogeneity occurs within the same tumor mass thought of as “microenvironmental metabolic nesting”. Furthermore, recent findings show that mutations of metabolic genes arise in the majority of tumors providing an opportunity for the development of more robust metabolic models of an individual patient’s tumor. The focus of this review is on the mechanisms governing this metabolic heterogeneity in breast cancer.

Performance of faecal indicator bacteria, microbial source tracking, and pollution risk mapping in tropical water

Faecal indicator bacteria (FIB) are used for the assessment of faecal pollution and possible water quality deterioration. There is growing evidence that FIB used in temperate regions are not adequate and reliable to detect faecal pollution in tropical regions. Hence, this study evaluated the adequacy of FIB, including total coliforms (TC), Escherichia coli (EC), Enterococci (IEC), and Clostridium perfringens (CP) in the high-altitude, tropical country of Ethiopia. In addition to FIB, for microbial source tracking (MST), a ruminant-associated molecular marker was applied at different water types and altitudes, and faecal pollution risk mapping was conducted based on consensus FIB. The performances of the indicators were evaluated at 22 sites from different water types. The results indicate that EC cell enumeration and CP spore determination perform well for faecal contamination monitoring. Most of the sub-basins of Lake Tana were found to be moderately to highly polluted, and the levels of pollution were demonstrated to be higher in the rainy season than in the post-rainy season. Markers associated with ruminants (BacR) were identified in more than three quarters of the sites. A bacterial pollution risk map was developed for sub-basins of Lake Tana, including the un-gauged sub-basins. We demonstrate how bacterial pollution risk mapping can aid in improvements to water quality testing and reduce risk to the general population from stream bacteria.

Influence of seasonality on the aerosol microbiome of the Amazon rainforest

The Amazon rainforest is the world's largest tropical forest, and this biome may be a significant contributor to primary biological aerosol (PBA) emissions on a global scale. These aerosols also play a pivotal role in modulating ecosystem dynamics, dispersing biological material over geographic barriers and influencing climate through radiation absorption, light scattering, or acting as cloud condensation nuclei. Despite their importance, there are limited studies investigating the effect of environmental variables on the bioaerosol composition in the Amazon rainforest. Here we present a 16S rRNA gene-based amplicon sequencing approach to investigate the bacterial microbiome in aerosols of the Amazon rainforest during distinct seasons and at different heights above the ground. Our data revealed that seasonal changes in temperature, relative humidity, and precipitation are the primary drivers of compositional changes in the Amazon rainforest aerosol microbiome. Interestingly, no significant differences were observed in the bacterial community composition of aerosols collected at ground and canopy levels. The core airborne bacterial families present in Amazon aerosol were Enterobacteriaceae, Beijerinckiaceae, Polyangiaceae, Bacillaceae and Ktedonobacteraceae. By correlating the bacterial taxa identified in the aerosol with literature data, we speculate that the phyllosphere may be one possible source of airborne bacteria in the Amazon rainforest. Results of this study indicate that the aerosol microbiota of the Amazon Rainforest are fairly diverse and principally impacted by seasonal changes in temperature and humidity.

Measuring Environmental Exposure to Enteric Pathogens in Low-Income Settings: Review and Recommendations of an Interdisciplinary Working Group

Infections with enteric pathogens impose a heavy disease burden, especially among young children in low-income countries. Recent findings from randomized controlled trials of water, sanitation, and hygiene interventions have raised questions about current methods for assessing environmental exposure to enteric pathogens. Approaches for estimating sources and doses of exposure suffer from a number of shortcomings, including reliance on imperfect indicators of fecal contamination instead of actual pathogens and estimating exposure indirectly from imprecise measurements of pathogens in the environment and human interaction therewith. These shortcomings limit the potential for effective surveillance of exposures, identification of important sources and modes of transmission, and evaluation of the effectiveness of interventions. In this review, we summarize current and emerging approaches used to characterize enteric pathogen hazards in different environmental media as well as human interaction with those media (external measures of exposure), and review methods that measure human infection with enteric pathogens as a proxy for past exposure (internal measures of exposure). We draw from lessons learned in other areas of environmental health to highlight how external and internal measures of exposure can be used to more comprehensively assess exposure. We conclude by recommending strategies for advancing enteric pathogen exposure assessments.

Microbial Indicators of Fecal Pollution: Recent Progress and Challenges in Assessing Water Quality

PURPOSE OF REVIEW

Fecal contamination of water is a major public health concern. This review summarizes recent developments and advancements in water quality indicators of fecal contamination.

RECENT FINDINGS

This review highlights a number of trends. First, fecal indicators continue to be a valuable tool to assess water quality and have expanded to include indicators able to detect sources of fecal contamination in water. Second, molecular methods, particularly PCR-based methods, have advanced considerably in their selected targets and rigor, but have added complexity that may prohibit adoption for routine monitoring activities at this time. Third, risk modeling is beginning to better connect indicators and human health risks, with the accuracy of assessments currently tied to the timing and conditions where risk is measured. Research has advanced although challenges remain for the effective use of both traditional and alternative fecal indicators for risk characterization, source attribution and apportionment, and impact evaluation.

The challenge of achieving safely managed drinking water supply on San Cristobal island, Galápagos

Achievement of United Nations Sustainable Development Goal 6.1 centers on the availability of a safely managed drinking water source for all. However, meeting the criteria for this goal is challenging on island systems and elsewhere with limited freshwater supplies. We measured microbial and chemical water quality over three years on San Cristobal Island, Galapagos, an island with limited freshwater supply, necessitating use of cisterns or roof tanks to ensure water availability in households. Our results showed that the municipal water treatment plants generally produced high quality drinking water but detection of Escherichia coli in 2-30% of post-treatment distribution samples suggests contamination and/or regrowth during distribution and storage. Linear regression revealed a modest, negative relationship between residual chlorine and microbial concentrations in drinking water samples, while 24-h antecedent rainfall only slightly increased microbial counts. Taken together, our results underscore the challenge of providing a safely managed drinking water source where limited freshwater quantities result in intermittent flow and require storage at the household level. Efforts to meet sustainable development goals for island systems will likely need to consider water availability for any treatment technologies or programs aimed at meeting water quality goals.

Human fecal contamination of water, soil, and surfaces in households sharing poor-quality sanitation facilities in Maputo, Mozambique

Identifying the origin of fecal contamination can support more effective interventions to interrupt enteric pathogen transmission. Microbial source tracking (MST) assays may help to identify environmental routes of pathogen transmission although these assays have performed poorly in highly contaminated domestic settings, highlighting the importance of both diagnostic validation and understanding the context-specific ecological, physical, and sociodemographic factors driving the spread of fecal contamination. We assessed fecal contamination of compounds (clusters of 2-10 households that share sanitation facilities) in low-income neighborhoods of urban Maputo, Mozambique, using a set of MST assays that were validated with animal stool and latrine sludge from study compounds. We sampled five environmental compartments involved in fecal microbe transmission and exposure: compound water source, household stored water and food preparation surfaces, and soil from the entrance to the compound latrine and the entrances to each household. Each sample was analyzed by culture for the general fecal indicator Escherichia coli (cEC) and by real-time PCR for the E. coli molecular marker EC23S857, human-associated markers HF183/BacR287 and Mnif, and GFD, an avian-associated marker. We collected 366 samples from 94 households in 58 compounds. At least one microbial target (indicator organism or marker gene) was detected in 96% of samples (353/366), with both E. coli targets present in the majority of samples (78%). Human targets were frequently detected in soils (59%) and occasionally in stored water (17%) but seldom in source water or on food surfaces. The avian target GFD was rarely detected in any sample type but was most common in soils (4%). To identify risk factors of fecal contamination, we estimated associations with sociodemographic, meteorological, and physical sample characteristics for each microbial target and sample type combination using Bayesian censored regression for target concentration responses and Bayesian logistic regression for target detection status. Associations with risk factors were generally weak and often differed in direction between different targets and sample types, though relationships were somewhat more consistent for physical sample characteristics. Wet soils were associated with elevated concentrations of cEC and EC23S857 and odds of detecting HF183. Water storage container characteristics that expose the contents to potential contact with hands and other objects were weakly associated with human target detection. Our results describe a setting impacted by pervasive domestic fecal contamination, including from human sources, that was largely disconnected from the observed variation in socioeconomic and sanitary conditions. This pattern suggests that in such highly contaminated settings, transformational changes to the community environment may be required before meaningful impacts on fecal contamination can be realized.

Predictors of Enteric Pathogens in the Domestic Environment from Human and Animal Sources in Rural Bangladesh

Fecal indicator organisms are measured to indicate the presence of fecal pollution, yet the association between indicators and pathogens varies by context. The goal of this study was to empirically evaluate the relationships between indicator Escherichia coli, microbial source tracking markers, select enteric pathogen genes, and potential sources of enteric pathogens in 600 rural Bangladeshi households. We measured indicators and pathogen genes in stored drinking water, soil, and on mother and child hands. Additionally, survey and observational data on sanitation and domestic hygiene practices were collected. Log10 concentrations of indicator E. coli were positively associated with the prevalence of pathogenic E. coli genes in all sample types. Given the current need to rely on indicators to assess fecal contamination in the field, it is significant that in this study context indicator E. coli concentrations, measured by IDEXX Colilert-18, provided quantitative information on the presence of pathogenic E. coli in different sample types. There were no significant associations between the human fecal marker (HumM2) and human-specific pathogens in any environmental sample type. There was an increase in the prevalence of Giardia lamblia genes, any E. coli virulence gene, and the specific E. coli virulence genes stx1/2 with every log10 increase in the concentration of the animal fecal marker (BacCow) on mothers' hands. Thus, domestic animals were important contributors to enteric pathogens in these households.

Variation of Bacterial Communities with Water Quality in an Urban Tropical Catchment

A major challenge for assessment of water quality in tropical environments is the natural occurrence and potential growth of Fecal Indicator Bacteria (FIB). To gain a better understanding of the relationship between measured levels of FIB and the distribution of sewage-associated bacteria, including potential pathogens, in the tropics this study compared the abundance of FIB (Total coliforms and E. coli) and the Bacteroidales (HF183 marker) with bacterial community structure determined by next-generation amplicon sequencing. Water was sampled twice over 6 months from 18 sites within a tropical urban catchment and reservoir, followed by extraction of DNA from microorganisms, and sequencing targeting the V3-V4 region of the 16S rRNA gene. Multivariate statistical analyses indicated that bacterial community composition (BCC) varied between reservoir and catchment, within catchment land-uses, and with E. coli concentration. Beta-regression indicated that the proportion of sequences from sewage-associated taxa (SAT) or pathogen-like sequences (PLS) were predicted most significantly by measured levels of E. coli(log MPN/100 mL) (χ² > 8.7; p < 0.003). In addition, SAT were significantly predicted by log HF183 levels (χ²=13.1; p = 0.0003) while PLS were not. Our study suggests that measurements of E. coli concentration could be useful in predicting samples enriched in sewage-associated and pathogen-like bacteria in tropical environments despite the potential for nonconservative behavior.

Seasonality of Coliform Bacteria Detection Rates in New Jersey Domestic Wells

It is important that indicators of fecal pollution are reliable. Coliform bacteria are a commonly used indicator of fecal pollution. As other investigators have reported elsewhere, we observed a seasonal pattern of coliform bacteria detections in domestic wells in New Jersey. Examination of a statewide database of 10 years of water quality data from 93,447 samples, from 78,207 wells, generated during real estate transactions, revealed that coliform bacteria were detected in a higher proportion of wells during warm weather months. Further examination of the seasonal pattern of other data, including well water pH, precipitation, ground and surface water temperatures, surface water coliform bacteria concentrations, and vegetation, resulted in the hypothesis that these bacteria may be derived from nonfecal (or environmentally adapted) as well as fecal sources. We provide evidence that the coliform seasonality may be the result of seasonal changes in groundwater extraction volumes (and to a lesser extent precipitation), and temperature-driven changes in the concentration of surface or near-surface coliform sources. Nonfecal coliform sources may not indicate the presence of fecal wastes and hence the potential presence of pathogens, or do so in an inconsistent fashion. Additional research is needed to identify the sources of the coliforms detected in groundwater.

Integrated Multivariate Analysis with Nondetects for the Development of Human Sewage Source-Tracking Tools Using Bacteriophages of Enterococcus faecalis

We developed sewage-specific microbial source tracking (MST) tools using enterococci bacteriophages and evaluated their performance with univariate and multivariate analyses involving data below detection limits. Newly isolated Enterococci faecalis bacterial strains AIM06 (DSM100702) and SR14 (DSM100701) demonstrated 100% specificity and 90% sensitivity to human sewage without detecting 68 animal manure pooled samples of cats, chickens, cows, dogs, ducks, pigs, and pigeons. AIM06 and SR14 bacteriophages were present in human sewage at 2-4 orders of magnitude. A principal component analysis confirmed the importance of both phages as main water quality parameters. The phages presented only in the polluted water, as classified by a cluster analysis, and at median concentrations of 1.71 × 10² and 4.27 × 10² PFU/100 mL, respectively, higher than nonhost specific RYC2056 phages and sewage-specific KS148 phages (p < 0.05). Interestingly, AIM06 and SR14 phages exhibited significant correlations with each other and with total coliforms, E. coli, enterococci, and biochemical oxygen demand (Kendall's tau = 0.348 to 0.605, p < 0.05), a result supporting their roles as water quality indicators. This research demonstrates the multiregional applicability of enterococci hosts in MST application and highlights the significance of multivariate analysis with nondetects in evaluating the performance of new MST host strains.

Assessing the microbial quality of a tropical watershed with an urbanization gradient using traditional and alternate fecal indicators

Urbanization affects the microbial loading into tropical streams, but its impact on water quality varies across watersheds. Rainfall in tropical environments also complicates microbial dynamics due to high seasonal and annual variations. Understanding the dynamics of fecal contamination in tropical surface waters may be further hindered by limitations from the utilization of traditional microbial indicators. We measured traditional (Enterococcus spp. and Escherichia coli), as well as alternate (enterophages and coliphages) indicators of fecal contamination in a tropical watershed in Puerto Rico during a 1-year period, and examined their relationship with rainfall events across an urbanization gradient. Enterococcus spp. and E. coli concentrations were 4 to 5 logs higher in non-urbanized or pristine sites when compared to enterophages and coliphages, suggesting that traditional fecal indicator bacteria may be natural inhabitants of pristine tropical waters. All of the tested indicators were positively correlated with rainfall and urbanization, except in the most urbanized sites, where rainfall may have had a dilution effect. The present study indicates that utilizing novel indicators of microbial water quality may improve the assessment of fecal contamination and pathogen risk for tropical watersheds.

The hyporheic zone and its functions: revision and research status in Neotropical regions

AbstractThe hyporheic zone (HZ), as the connecting ecotone between surface- and groundwater, is functionally part of both fluvial and groundwater ecosystems. Its hydrological, chemical, biological and metabolic features are specific of this zone, not belonging truly neither to surface- nor to groundwater. Exchanges of water, nutrients, and organic matter occur in response to variations in discharge and bed topography and porosity. Dynamic gradients exist at all scales and vary temporally. Across all scales, the functional significance of the HZ relates to its activity and connection with the surface stream. The HZ is a relatively rich environment and almost all invertebrate groups have colonized this habitat. This fauna, so-called hyporheos, is composed of species typical from interstitial environment, and also of benthic epigean and phreatic species. The hyporheic microbiocenose consists in bacteria, archaea, protozoa and fungi. The HZ provides several ecosystem services, playing a pivotal role in mediating exchange processes, including both matter and energy, between surface and subterranean ecosystems, functioning as regulator of water flow, benthic invertebrates refuge and place of storage, source and transformation of organic matter. The hyporheic zone is one of the most threatened aquatic environments, being strongly influenced by human activities, and the least protected by legislation worldwide. Its maintenance and conservation is compelling in order to preserve the ecological interconnectivity among the three spatial dimensions of the aquatic environment. Although several researchers addressed the importance of the hyporheic zone early, and most contemporary stream ecosystem models explicitly include it, very little is known about the HZ of Neotropical regions. From a biological standpoint, hyporheos fauna in Neotropical regions are still largely underestimated. This review focuses on a brief presentation of the hyporheic zone and its functions and significance as an ecotone. We also highlighted the key aspects considering also the current status of research in Neotropical regions.

A Survey of Escherichia coli and Salmonella in the Hyporheic Zone of a Subtropical Stream: Their Bacteriological, Physicochemical and Environmental Relationships

The Hyporheic Zone is among the most important interstitial freshwater habitats, but the relationship between biotic and abiotic factors in this zone remains under-explored. Enterobacteria were expected to be present, but no specific studies had ever confirmed this prediction. The aim of this study was, therefore, to evaluate the total coliforms, Escherichia coli and Salmonella spp. in hyporheic water and to determine the relationship of the physical, chemical and environmental factors at different depths in a rainforest stream. To this end, thirty-six water samples were collected at three depths in sites located in the first, second and third orders in diverse substrates. The total coliforms, Escherichia coli and Salmonella sp. were evaluated in terms of their CFU/ml. In the interstitial samples, coliforms were detected in 100% of the samples. The total coliform counts had higher values at intermediate depths, while E. coli and Salmonella spp. instead had higher values at intermediate and large depths, often reaching or exceeding the values of the surface samples. Our results revealed that Salmonella spp. and the coliforms have different microhabitat preferences. Salmonella spp. and coliform species prefer deposition areas, such as lateral sides of pools, curves and bars, but they have a tendency to distribute into different depths, likely due to temperature differences. Salmonella spp. prefer compact substrata, with fewer fluids passing through and with upwelling areas with lower oxygen inflow. The coliform species showed the opposite preference. Our results suggest that bacterial variation is related to environmental factors and physical-chemical parameters within the HZ and may play a key role in the microbial diversity and distribution in these ecosystems.

Associations of chemical tracers and faecal indicator bacteria in a tropical urban catchment

Surface water contamination by human faecal wastes is a widespread hazard for human health. Faecal indicator bacteria (FIB) are the most widely used indicators to assess surface water quality but are less-human-specific and have the potential to survive longer and/or occur naturally in tropical areas. In this study, 13 wastewater chemicals (chloride, boron, orthosphophate, detergents as methylene blue active substances, cholesterol, cholestanol, coprostanol, diethylhexyl phthalate, caffeine, acetaminophen, ibuprofen, sucralose and saccharin) were investigated in order to evaluate tracers for human faecal and sewage contamination in tropical urban catchments. Surface water samples were collected at an hourly interval from sampling locations with distinct major land uses: high-density residential, low-density residential, commercial and industrial. Measured concentrations were analysed to investigate the association among indicators and tracers for each land-use category. Better correlations were found between different indicators and tracers in each land-use dataset than in the dataset for all land uses, which shows that land use is an important determinant of drain water quality. Data were further segregated based on the hourly FIB concentrations. There were better correlations between FIB and chemical tracers when FIB concentrations were higher. Therefore, sampling programs must be designed carefully to take the time of sampling and land use into account in order to effectively assess human faecal and sewage contamination in urban catchments. FIB is recommended as the first tier in assessment of surface water quality impairment and chemical tracers as the second tier. Acetaminophen and coprostanol are recommended as chemical tracers for high-density residential areas, while chloride, coprostanol and caffeine are recommended for low-density residential areas.

A short review of fecal indicator bacteria in tropical aquatic ecosystems: knowledge gaps and future directions

Given the high numbers of deaths and the debilitating nature of diseases caused by the use of unclean water it is imperative that we have an understanding of the factors that control the dispersion of water borne pathogens and their respective indicators. This is all the more important in developing countries where significant proportions of the population often have little or no access to clean drinking water supplies. Moreover, and notwithstanding the importance of these bacteria in terms of public health, at present little work exists on the persistence, transfer and proliferation of these pathogens and their respective indicator organisms, e.g., fecal indicator bacteria (FIB) such as Escherichia coli and fecal coliforms in humid tropical systems, such as are found in South East Asia or in the tropical regions of Africa. Both FIB and the waterborne pathogens they are supposed to indicate are particularly susceptible to shifts in water flow and quality and the predicted increases in rainfall and floods due to climate change will only exacerbate the problems of contamination. This will be furthermore compounded by the increasing urbanization and agricultural intensification that developing regions are experiencing. Therefore, recognizing and understanding the link between human activities, natural process and microbial functioning and their ultimate impacts on human health are prerequisites for reducing the risks to the exposed populations. Most of the existing work in tropical systems has been based on the application of temperate indicator organisms, models and mechanisms regardless of their applicability or appropriateness for tropical environments. Here, we present a short review on the factors that control FIB dynamics in temperate systems and discuss their applicability to tropical environments. We then highlight some of the knowledge gaps in order to stimulate future research in this field in the tropics.

Microbes in Beach Sands: Integrating Environment, Ecology and Public Health

Beach sand is a habitat that supports many microbes, including viruses, bacteria, fungi and protozoa (micropsammon). The apparently inhospitable conditions of beach sand environments belie the thriving communities found there. Physical factors, such as water availability and protection from insolation; biological factors, such as competition, predation, and biofilm formation; and nutrient availability all contribute to the characteristics of the micropsammon. Sand microbial communities include autochthonous species/phylotypes indigenous to the environment. Allochthonous microbes, including fecal indicator bacteria (FIB) and waterborne pathogens, are deposited via waves, runoff, air, or animals. The fate of these microbes ranges from death, to transient persistence and/or replication, to establishment of thriving populations (naturalization) and integration in the autochthonous community. Transport of the micropsammon within the habitat occurs both horizontally across the beach, and vertically from the sand surface and ground water table, as well as at various scales including interstitial flow within sand pores, sediment transport for particle-associated microbes, and the large-scale processes of wave action and terrestrial runoff. The concept of beach sand as a microbial habitat and reservoir of FIB and pathogens has begun to influence our thinking about human health effects associated with sand exposure and recreational water use. A variety of pathogens have been reported from beach sands, and recent epidemiology studies have found some evidence of health risks associated with sand exposure. Persistent or replicating populations of FIB and enteric pathogens have consequences for watershed/beach management strategies and regulatory standards for safe beaches. This review summarizes our understanding of the community structure, ecology, fate, transport, and public health implications of microbes in beach sand. It concludes with recommendations for future work in this vastly under-studied area.

Tank bromeliad water: similar or distinct environments for research of bacterial bioactives?

The Atlantic Rainforest does not have a uniform physiognomy, its relief determines different environmental conditions that define the composition of its flora and fauna. Within this ecosystem, bromeliads that form tanks with their leaves hold water reservoirs throughout the year, maintaining complex food chains, based mainly on autotrophic and heterotrophic bacteria. Some works concluded that the water held by tank bromeliads concentrate the microbial diversity of their ecosystem. To investigate the bacterial diversity and the potential biotechnology of these ecosystems, tank bromeliads of the Neoregelia cruenta species from the Atlantic Rainforest in Brazil were used as models for this research. Bacteria isolated from these models were tested for production of bioactive compounds. DGGE of the water held by tank bromeliads was performed in different seasons, locations and sun exposure to verify whether these environmental factors affect bacterial communities. The DGGE bands profile showed no grouping of bacterial community by the environmental factors tested. Most of the isolates demonstrated promising activities in the tests performed. Collectively, these results suggest that tank bromeliads of the N. cruenta species provide important habitats for a diverse microbial community, suggesting that each tank forms a distinct micro-habitat. These tanks can be considered excellent sources for the search for new enzymes and/or new bioactive composites of microbial origin.

Fecal contamination of drinking-water in low- and middle-income countries: a systematic review and meta-analysis

BACKGROUND

Access to safe drinking-water is a fundamental requirement for good health and is also a human right. Global access to safe drinking-water is monitored by WHO and UNICEF using as an indicator "use of an improved source," which does not account for water quality measurements. Our objectives were to determine whether water from "improved" sources is less likely to contain fecal contamination than "unimproved" sources and to assess the extent to which contamination varies by source type and setting.

METHODS AND FINDINGS

Studies in Chinese, English, French, Portuguese, and Spanish were identified from online databases, including PubMed and Web of Science, and grey literature. Studies in low- and middle-income countries published between 1990 and August 2013 that assessed drinking-water for the presence of Escherichia coli or thermotolerant coliforms (TTC) were included provided they associated results with a particular source type. In total 319 studies were included, reporting on 96,737 water samples. The odds of contamination within a given study were considerably lower for "improved" sources than "unimproved" sources (odds ratio [OR] = 0.15 [0.10-0.21], I2 = 80.3% [72.9-85.6]). However over a quarter of samples from improved sources contained fecal contamination in 38% of 191 studies. Water sources in low-income countries (OR = 2.37 [1.52-3.71]; p<0.001) and rural areas (OR = 2.37 [1.47-3.81] p<0.001) were more likely to be contaminated. Studies rarely reported stored water quality or sanitary risks and few achieved robust random selection. Safety may be overestimated due to infrequent water sampling and deterioration in quality prior to consumption.

CONCLUSION

Access to an "improved source" provides a measure of sanitary protection but does not ensure water is free of fecal contamination nor is it consistent between source types or settings. International estimates therefore greatly overstate use of safe drinking-water and do not fully reflect disparities in access. An enhanced monitoring strategy would combine indicators of sanitary protection with measures of water quality.

Distribution and abundance of human-specific Bacteroides and relation to traditional indicators in an urban tropical catchment

AIMS

The study goals were to determine the relationship between faecal indicator bacteria (FIB), the HF183 marker and land use, and the phylogenetic diversity of HF183 marker sequences in a tropical urban watershed.

METHODS AND RESULTS

Total coliforms, Escherichia coli, and HF183 were quantified in 81 samples categorized as undeveloped, residential and horticultural from the Kranji Reservoir and Catchment in Singapore. Quantitative-PCR for HF183 followed by analysis of variance indicated that horticultural areas had significantly higher geometric means for marker levels (4·3 × 10(4) HF183-GE 100 ml(-1)) than nonhorticultural areas (3·07 × 10(3) HF183-GE 100 ml(-1)). E. coli and HF183 were moderately correlated in horticultural areas (R = 0·59, P = 0·0077), but not elsewhere in the catchment. Initial upstream surveys of candidate sources revealed elevated HF183 in a wastewater treatment effluent but not in aquaculture ponds. The HF183 marker was cloned, sequenced and determined by phylogenetic analysis to match the original marker description.

CONCLUSION

We show that quantification of the HF183 marker is a useful tool for mapping the spatial distribution and potential sources of human sewage contamination in tropical environments such as Singapore.

SIGNIFICANCE AND IMPACT

A major challenge for assessment of water quality in tropical environments is the natural occurrence and nonconservative behaviour of FIB. The HF183 marker has been employed in temperate environments as an alternative indicator for human sewage contamination. Our study supports the use of the HF183 marker as an indicator for human sewage in Singapore and motivates further work to determine HF183 marker levels that correspond to public health risk in tropical environments.

Antibiotic-resistance and virulence genes in Enterococcus isolated from tropical recreational waters

The prevalence of enterococci harboring tetracycline- and vancomycin-resistance genes, as well as the enterococcal surface protein (esp) has mostly been determined in clinical settings, but their prevalence in tropical recreational waters remains largely unknown. The present study determined the prevalence of tetM (tetracycline-resistance), vanA and vanB (vancomycin-resistance) in the bacterial and viral fractions, enterococci and their induced phages isolated from tropical recreational marine and fresh waters, dry and wet sands. Since lysogenic phages can act as vectors for antibiotic-resistance and virulence factors, the prevalence of the mentioned genes, as well as that of an integrase-encoding gene (int) specific for Enterococcus faecalis phages was determined. Up to 60 and 54% of the bacterial fractions and enterococci, respectively, harbored at least one of the tested genes suggesting that bacteria in tropical environments may be reservoirs of antibiotic-resistance and virulence genes. int was detected in the viral fractions and in one Enterococcus isolate after induction. This study presents the opportunity to determine if the presence of bacteria harboring antibiotic-resistance and virulence genes in tropical recreational waters represents a threat to public health.

H2S as an indicator of water supply vulnerability and health risk in low-resource settings: a prospective cohort study

In this large-scale longitudinal study conducted in rural Southern India, we compared a presence/absence hydrogen sulfide (H2S) test with quantitative assays for total coliforms and Escherichia coli as measures of water quality, health risk, and water supply vulnerability to microbial contamination. None of the three indicators showed a significant association with child diarrhea. The presence of H2S in a water sample was associated with higher levels of total coliform species that may have included E. coli but that were not restricted to E. coli. In addition, we observed a strong relationship between the percent positive H2S test results and total coliform levels among water source samples (R(2) = 0.87). The consistent relationships between H2S and total coliform levels indicate that presence/absence of H2S tests provide a cost-effective option for assessing both the vulnerability of water supplies to microbial contamination and the results of water quality management and risk mitigation efforts.

Tracking the primary sources of fecal pollution in a tropical watershed in a one-year study

A study was conducted to determine the primary sources of fecal pollution in a subtropical watershed using host-specific assays developed in temperate regions. Water samples (n = 534) from 10 different sites along the Rio Grande de Arecibo (RGA) watershed were collected mostly on a weekly basis (54 sampling events) during 13 months. DNA extracts from water samples were used in PCR assays to determine the occurrence of fecal bacteria (Bacteroidales, Clostridium coccoides, and enterococci) and human-, cattle-, swine-, and chicken-specific fecal sources. Feces from 12 different animals (n = 340) and wastewater treatment samples (n = 16) were analyzed to determine the specificity and distribution of host-specific assays. The human-specific assay (HF183) was found to be highly specific, as it did not cross-react with nontarget samples. The cattle marker (CF128) cross-reacted to some extent with swine, chicken, and turkeys and was present in 64% of the cattle samples tested. The swine assays showed poor host specificity, while the three chicken assays showed poor host distribution. Differences in the detection of host-specific markers were noted per site. While human and cattle assays showed moderate average detection rates throughout the watershed, areas impacted by wastewater treatment plants and cattle exhibited the highest prevalence of these markers. When conditional probability for positive signals was determined for each of the markers, the results indicated higher confidence levels for the human assay and lower levels for all the other assays. Overall, the results from this study suggest that additional assays are needed, particularly to track cattle, chicken, and swine fecal pollution sources in the RGA watershed. The results also suggest that the geographic stability of genetic markers needs to be determined prior to conducting applied source tracking studies in tropical settings.

Hands and water as vectors of diarrheal pathogens in Bagamoyo, Tanzania

Diarrheal disease is a leading cause of under-five childhood mortality worldwide, with at least half of these deaths occurring in sub-Saharan Africa. Transmission of diarrheal pathogens occurs through several exposure routes including drinking water and hands, but the relative importance of each route is not well understood. Using molecular methods, this study examines the relative importance of different exposure routes by measuring enteric bacteria (pathogenic Escherichia coli) and viruses (rotavirus, enterovirus, adenovirus) in hand rinses, stored water, and source waters in Bagamoyo, Tanzania. Viruses were most frequently found on hands, suggesting that hands are important vectors for viral illness. The occurrence of E. coli virulence genes (ECVG) was equivalent across all sample types, indicating that both water and hands are important for bacterial pathogen transmission. Fecal indicator bacteria and turbidity were good predictors of ECVG, whereas turbidity and human-specific Bacteroidales were good predictors of viruses. ECVG were more likely found in unimproved water sources, but both ECVG and viral genes were detected in improved water sources. ECVG were more likely found in stored water of households with unimproved sanitation facilities. The results provide insights into the distribution of pathogens in Tanzanian households and offer evidence that hand-washing and improved water management practices could alleviate viral and bacterial diarrhea.

Evidence for occurrence, persistence, and growth potential of Escherichia coli and enterococci in Hawaii's soil environments

High densities of Escherichia coli and enterococci are common in freshwaters on Oahu and other Hawaiian Islands. Soil along stream banks has long been suspected as the likely source of these bacteria; however, the extent of their occurrence and distribution in a wide range of soils remained unknown until the current investigation. Soil samples representing the seven major soil associations were collected on the island of Oahu and analyzed for fecal coliforms, E. coli, and enterococci by the most probable number method. Fecal coliforms, E. coli, and enterococci were found in most of the samples analyzed; log mean densities (MPN ± SE g soil⁻¹) were 1.96±0.18, n=61; 1.21±0.17, n=57; and 2.99±0.12, n=62, respectively. Representative, presumptive cultures of E. coli and enterococci collected from the various soils were identified and further speciated using the API scheme; at least six species of Enterococcus, including Enterococcus faecalis and Enterococcus faecium, were identified. In mesocosm studies, E. coli and enterococci increased by 100-fold in 4 days, after mixing sewage-spiked soil (one part) with autoclaved soil (nine parts). E. coli remained metabolically active in the soil and readily responded to nutrients, as evidenced by increased dehydrogenase activity. Collectively, these findings indicate that populations of E. coli and enterococci are part of the natural soil microflora, potentially influencing the quality of nearby water bodies.

Interrelationships of food safety and plant pathology: the life cycle of human pathogens on plants

Bacterial food-borne pathogens use plants as vectors between animal hosts, all the while following the life cycle script of plant-associated bacteria. Similar to phytobacteria, Salmonella, pathogenic Escherichia coli, and cross-domain pathogens have a foothold in agricultural production areas. The commonality of environmental contamination translates to contact with plants. Because of the chronic absence of kill steps against human pathogens for fresh produce, arrival on plants leads to persistence and the risk of human illness. Significant research progress is revealing mechanisms used by human pathogens to colonize plants and important biological interactions between and among bacteria in planta. These findings articulate the difficulty of eliminating or reducing the pathogen from plants. The plant itself may be an untapped key to clean produce. This review highlights the life of human pathogens outside an animal host, focusing on the role of plants, and illustrates areas that are ripe for future investigation.

Microbial quality of tropical inland waters and effects of rainfall events

Novel markers of fecal pollution in tropical waters are needed since conventional methods recommended for other geographical regions may not apply. To address this, the prevalence of thermotolerant coliforms, enterococci, coliphages, and enterophages was determined by culture methods across a watershed. Additionally, human-, chicken-, and cattle-specific PCR assays were used to identify potential fecal pollution sources in this watershed. An enterococcus quantitative PCR (qPCR) assay was tested and correlated with culture methods at three sites since water quality guidelines could incorporate this technique as a rapid detection method. Various rainfall events reported before sample collection at three sites were considered in the data analyses. Thermotolerant coliforms, enterococci, coliphages, and enterophages were detected across the watershed. Human-specific Bacteroides bacteria, unlike the cattle- and chicken-specific bacteria, were detected mostly at sites with the corresponding fecal impact. Enterococci were detected by qPCR as well, but positive correlations with the culture method were noted at two sites, suggesting that either technique could be used. However, no positive correlations were noted for an inland lake tested, suggesting that qPCR may not be suitable for all water bodies. Concentrations of thermotolerant coliforms and bacteriophages were consistently lower after rainfall events, pointing to a possible dilution effect. Rainfall positively correlated with enterococci detected by culturing and qPCR, but this was not the case for the inland lake. The toolbox of methods and correlations presented here could be potentially applied to assess the microbial quality of various water types.

Rethinking indicators of microbial drinking water quality for health studies in tropical developing countries: case study in northern coastal Ecuador

To address the problem of the health impacts of unsafe drinking water, methods are needed to assess microbiologic contamination in water. However, indicators of water quality have provided mixed results. We evaluate five assays (three for Escherichia coli and one each for enterococci and somatic coliphage) of microbial contamination in villages in rural Ecuador that rely mostly on untreated drinking water. Only membrane filtration for E. coli using mI agar detected a significant association with household diarrheal disease outcome (odds ratio = 1.29, 95% confidence interval = 1.02-1.65 in household containers and odds ratio = 1.18, 95% confidence interval = 1.02-1.37) in source samples. Our analysis and other published research points to the need for further consideration of study design factors, such as sample size and variability in measurements, when using indicator organisms, especially when relating water quality exposure to health outcomes. Although indicator organisms are used extensively in health studies, we argue that their use requires a full understanding of their purposes and limitations.

Assessment of drinking water quality using ICP-MS and microbiological methods in the Bholakpur area, Hyderabad, India

A total of 16 people died and over 500 people were hospitalized due to diarrhoeal illness in the Bholakpur area of Hyderabad, India on 6th May 2009. A study was conducted with immediate effect to evaluate the quality of municipal tap water of the Bholakpur locality. The study consists of the determination of physico-chemical properties, trace metals, heavy metals, rare earth elements and microbiological quality of drinking water. The data showed the variation of the investigated parameters in samples as follows: pH 7.14 to 8.72, EC 455 to 769 μS/cm, TDS 303.51 to 515.23 ppm and DO 1.01 to 6.83 mg/L which are within WHO guidelines for drinking water quality. The water samples were analyzed for 27 elements (Li, Be, B, Na, Mg, Al, Si, K, Ca, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Se, Rb, Sr, Mo, Ag, Cd, Sb, Ba and Pb) using inductively coupled plasma-mass spectrometry (ICP-MS). The concentrations of Fe (0.12 to 1.13 mg/L), Pb (0.01 to 0.07 mg/L), Cu (0.01 to 0.19 mg/L), Ni (0.01 to 0.15 mg/L), Al (0.16 to 0.49 mg/L), and Na (38.36 to 68.69 mg/L) were obtained, which exceed the permissible limits of the World Health Organization (WHO) for drinking water quality guidelines. The remaining elements were within the permissible limits. The microbiological quality of water was tested using standard plate count, membrane filtration technique, thermotolerant coliform (TTC), and most probable number (MPN) methods. The total heterotrophic bacteria ranged from 1.0 × 10(5) to 18 × 10(7 )cfu/ml. Total viable bacteria in all the water samples were found to be too numerable to count and total number of coliform bacteria in all water samples were found to be of order of 1,100 to >2,400 MPN index/100 ml. TTC tested positive for coliform bacteria at 44.2°C. All the water samples of the study area exceeded the permissible counts of WHO and that (zero and minimal counts) of the control site (National Geophysical Research Institute) water samples. Excessively high colony numbers indicate that the water is highly contaminated with microorganisms and is hazardous for drinking purposes. Bacteriological pollution of drinking water supplies caused diarrhoeal illness in Bholakpur, which is due to the infiltration of contaminated water (sewage) through cross connection, leakage points, and back siphoning.

Bacteria in beach sands: an emerging challenge in protecting coastal water quality and bather health

To protect bather health at recreational beaches, fecal indicator bacterial standards are used to monitor water quality, and waters exceeding the standards are subsequently closed to bathers. However beachgoers are also in contact with beach sands, the sanitary quality of which is not included within beach monitoring programs. In fact, sands and sediments provide habitat where fecal bacterial populations may persist, and in some cases grow, in the coastal zone. Specific pathogens are less well studied in beach sands and sediments, but there is a body of evidence that they too may persist in these environments. This paper reviews the current state of knowledge regarding the abundance and distribution of fecal indicator bacteria and pathogens in beach sands of diverse climatological regions, and at beaches subjected to varied levels of anthropogenic impact. In all regions fecal indicator bacteria are nearly ubiquitous in beach sands, and similar relationships emerge among fecal indicator abundance in dry sand, submerged sands, and water. Taken together, these studies contextualize a potential public health issue and identify research questions that must be addressed in order to support future policy decisions.

Sorbitol-fermenting Bifidobacteria are indicators of very recent human faecal pollution in streams and groundwater habitats in urban tropical lowlands

Sorbitol-fermenting Bifidobacteria (SFB) proved to be an excellent indicator of very recent human faecal pollution (hours to days) in the investigated tropical stream and groundwater habitats. SFB were recovered from human faeces and sources potentially contaminated with human excreta. SFB were undetectable in animal faeces and environmental samples not contaminated with human faeces. Microcosm studies demonstrated a rapid die-off rate in groundwater (T90 value 0.6 days) and stream water (T90 value 0.9-1.7 days). Discrimination sensitivity analysis, including E. coli, faecal coliforms, total coliforms and Clostridium perfringens spores, revealed high ability of SFB to distinguish differing levels of faecal pollution especially for streams although high background levels of interfering bacteria can complicate its recovery on the used medium. Due to its faster die-off, as compared to many waterborne pathogens, SFB cannot replace microbiological standard parameters for routine water quality monitoring but it is highly recommendable as a specific and complementary tool when human faecal pollution has to be localized or verified. Because of its exclusive faecal origin and human specificity it seems also worthwhile to include SFB in future risk evaluation studies at tropical water resources in order to evaluate under which situations risks of infection may be indicated.

Isolation and characterization of Bacteroides host strain HB-73 used to detect sewage specific phages in Hawaii

Previous studies have shown that Escherichia coli and enterococci are unreliable indicators of fecal contamination in Hawaii because of their ability to multiply in environmental soils. In this study, the method of detecting Bacteroides phages as specific markers of sewage contamination in Hawaii's recreational waters was evaluated because these sewage specific phages cannot multiply under environmental conditions. Bacteroides hosts (GB-124, GA-17), were recovered from sewage samples in Europe and were reported to be effective in detecting phages from sewage samples obtained in certain geographical areas. However, GB-124 and GA-17 hosts were ineffective in detecting phages from sewage samples obtained in Hawaii. Bacteroides host HB-73 was isolated from a sewage sample in Hawaii, confirmed as a Bacteroides sp. and shown to recover phages from multiple sources of sewage produced in Hawaii at high concentrations (5.2-7.3 x 10(5) PFU/100 mL). These Bacteroides phages were considered as potential markers of sewage because they also survived for three days in fresh stream water and two days in marine water. Water samples from Hawaii's coastal swimming beaches and harbors, which were known to be contaminated with discharges from streams, were shown to contain moderate (20-187 CFU/100 mL) to elevated (173-816 CFU/100 mL) concentrations of enterococci. These same samples contained undetectable levels (<10 PFU/100 mL) of F+ coliphage and Bacteroides phages and provided evidence to suggest that these enterococci may not necessarily be associated with the presence of raw sewage. These results support previous conclusions that discharges from streams are the major sources of enterococci in coastal waters of Hawaii and the most likely source of these enterococci is from environmental soil rather than from sewage.

Growth and survival of Escherichia coli and enterococci populations in the macro-alga Cladophora (Chlorophyta)

The macro-alga Cladophora glomerata is found in streams and lakes worldwide. High concentrations of Escherichia coli and enterococci have been reported in Cladophora along the Lake Michigan shore. The objective of this study was to determine if Cladophora supported growth of these indicator bacteria. Algal leachate readily supported in vitro multiplication of E. coli and enterococci, suggesting that leachates contain necessary growth-promoting substances. Growth was directly related to the concentration of algal leachate. E. coli survived for over 6 months in dried Cladophora stored at 4 degrees C; residual E. coli grew after mat rehydration, reaching a carrying capacity of 8 log CFU g(-1) in 48 h. Results of this study also show that the E. coli strains associated with Cladophora are highly related; in most instances they are genetically different from each other, suggesting that the relationship between E. coli and Cladophora may be casual. These findings indicate that Cladophora provides a suitable environment for indicator bacteria to persist for extended periods and to grow under natural conditions.

Rainfall simulation in greenhouse microcosms to assess bacterial-associated runoff from land-applied poultry litter

Runoff water following a rain event is one possible source of environmental contamination after a manure application. This greenhouse study used a rainfall simulator to determine bacterial-associated runoff from troughs of common bermudagrass [Cynodon dactylon (L.) Pers.] that were treated with P-based, N-based, and N plus lime rates of poultry (Gallus gallus) litter, recommended inorganic fertilizer, and control. Total heterotrophic plate count (HPC) bacteria, total and thermotolerant coliforms, enterococci, staphylococci, Clostridium perfringens, Salmonella, and Campylobacter, as well as antibiotic resistance profiles for the staphylococci and enterococci isolates were all monitored in runoff waters. Analysis following five rainfall events indicated that staphylococci, enterococci, and clostridia levels were related to manure application rate. Runoff release of staphylococci, enterococci, and C. perfringens were approximately 3 to 6 log10 greater in litter vs. control treatment. In addition, traditional indicators such as thermotolerant and total coliforms performed poorly as fecal indicators. Some isolated enterococci demonstrated increased antibiotic resistance to polymixin b and/or select aminoglyocosides, while many staphylococci were susceptible to most antimicrobials tested. Results indicated poultry litter application can lead to microbial runoff following simulated rain events. Future studies should focus on the use of staphylococci, enterococci, and C. perfringens as indicators.

A Preliminary Investigation of Fecal Indicator Bacteria, Human Pathogens, and Source Tracking Markers in Beach Water and Sand

Data suggesting that fecal indicating bacteria may persist and/or regrow in sand has raised concerns that fecal indicators may become uncoupled from sources of human fecal pollution. To investigate this possibility, wet and dry beach sand, beach water, riverine water, canal water, and raw sewage samples were screened by PCR for certain pathogenic microbes and molecular markers of human fecal pollution. The targets included in this study were human specific Bacteroides (HF8 marker), human-specific enterococci (esp gene), Staphylococcus aureus, Escherichia coli 0157:H7, Campylobacter jejuni, and adenovirus. Sewage samples were also tested for Salmonella species. The results were compared to concentrations of enterococci, Escherichia coli, and Bacteroides species, as determined by membrane filtration methods. Molecular analysis yielded positive results for human specific Bacteroides, and S. aureus, in samples of raw sewage. Two of the environmental samples were positive for human specific Bacteroides and one was positive for S. aureus. The PCR screen was negative for other samples and targets, despite exceedance of EPA single sample guidelines for recreational waters on several of the sample dates (5/11 dates). However, estimates of the number of cells delivered to the PCR reaction suggested that few of the samples met the detection limit of the PCR reaction due to a variety of factors. The analysis indicated a need to improve nucleic acid processing in order to enable better delivery of DNA to downstream molecular methods.

Forest fragmentation as cause of bacterial transmission among nonhuman primates, humans, and livestock, Uganda

We conducted a prospective study of bacterial transmission among humans, nonhuman primates (primates hereafter), and livestock in western Uganda. Humans living near forest fragments harbored Escherichia coli bacteria that were approximately 75% more similar to bacteria from primates in those fragments than to bacteria from primates in nearby undisturbed forests. Genetic similarity between human/livestock and primate bacteria increased approximately 3-fold as anthropogenic disturbance within forest fragments increased from moderate to high. Bacteria harbored by humans and livestock were approximately twice as similar to those of red-tailed guenons, which habitually enter human settlements to raid crops, than to bacteria of other primate species. Tending livestock, experiencing gastrointestinal symptoms, and residing near a disturbed forest fragment increased genetic similarity between a participant's bacteria and those of nearby primates. Forest fragmentation, anthropogenic disturbance within fragments, primate ecology, and human behavior all influence bidirectional, interspecific bacterial transmission. Targeted interventions on any of these levels should reduce disease transmission and emergence.

Escherichia coli O157 can grow in natural freshwater at low carbon concentrations

Whereas much information on the die-off of Escherichia coli in the aquatic environment is available, only few data support its growth under such conditions. We therefore investigated batch growth in microcosms containing different types of sterile freshwater. The water samples were inoculated with low starting cell concentrations of E. coli O157 (3 x 10(3) cells ml(-1)) and growth was followed using nucleic acid staining combined with flow cytometry. We demonstrated that E. coli O157 is able to grow in sterile freshwater at low carbon concentrations, which is against the common view that cell numbers decline over time when added to freshwater samples. A correlation between apparent assimilable organic carbon (AOC(app)) concentration and the final cell concentration reached by E. coli O157 was established (P < 0.01). A considerable fraction of the AOC(app) (34 +/- 13%) was used by E. coli O157 but the numerical cell yield was about five-times lower in comparison with the bacterial AOC-test community, which originated from natural freshwater. On average, the maximum specific growth rate (mu(max)) of E. coli O157 growing in sterile freshwater at 30 degrees C was 0.19 +/- 0.07 h(-1). Batch growth assays at five different temperatures revealed a positive influence of temperature on mu(max) of E. coli O157. The results give new information on the behaviour of this common pathogen in the aquatic environment and contribute to microbial risk assessment in order to prevent spreading of water-borne diseases.

Genetic diversity and population structure of Escherichia coli isolated from freshwater beaches

Escherichia coli is an important member of the gastrointestinal tract of humans and warm-blooded animals (primary habitat). In the external environment outside the host (secondary habitat), it is often considered to be only a transient member of the microbiota found in water and soil, although recent evidence suggests that some strains can persist in temperate soils and freshwater beaches. Here we quantified the population genetic structure of E. coli from a longitudinal collection of environmental strains isolated from six freshwater beaches along Lake Huron and the St. Clair River in Michigan. Multilocus enzyme electrophoresis (MLEE) and multilocus sequence typing (MLST) revealed extensive genetic diversity among 185 E. coli isolates with an average of 40 alleles per locus. Despite evidence for extensive recombination generating new alleles and genotypic diversity, several genotypes marked by distinct MLEE and MLST profiles were repeatedly recovered from separate sites at different times. A PCR-based phylogrouping technique showed that the persistent, naturalized E. coli belonged to the B1 group. These results support the hypothesis that persistent genotypes have an adaptive advantage in the secondary habitat outside the host.

Oceans and human health: Emerging public health risks in the marine environment

There has been an increasing recognition of the inter-relationship between human health and the oceans. Traditionally, the focus of research and concern has been on the impact of human activities on the oceans, particularly through anthropogenic pollution and the exploitation of marine resources. More recently, there has been recognition of the potential direct impact of the oceans on human health, both detrimental and beneficial. Areas identified include: global change, harmful algal blooms (HABs), microbial and chemical contamination of marine waters and seafood, and marine models and natural products from the seas. It is hoped that through the recognition of the inter-dependence of the health of both humans and the oceans, efforts will be made to restore and preserve the oceans.

Occurrence and growth characteristics ofEscherichia coliand enterococci within the accumulated fluid of the northern pitcher plant (Sarracenia purpureaL.)

Sarracenia purpurea L., a carnivorous bog plant (also known as the pitcher plant), represents an excellent model of a well-defined, self-contained ecosystem; the individual pitchers of the plant serve as a microhabitat for a variety of micro- and macro-organisms. Previously, fecal indicator bacteria (Escherichia coli and enterococci) were shown as incidental contaminants in pitcher fluid; however, whether their occurrence in pitcher fluid is incidental or common has not been established. The purpose of this study was to investigate the occurrence, distribution, and growth potential of E. coli and enterococci in pitcher plant fluid from a protected bog in northwest Indiana. Escherichia coli and enterococci were recovered in pitcher fluids (n = 43 plants), with mean densities (log CFU mL–1) of 1.28 ± 0.23 and 1.97 ± 0.27, respectively. In vitro experiments showed that E. coli growth in fluid not containing insects or indigenous organisms was directly proportional to the fluid concentration (growth was 10-fold in 24 h in 100% fluid); however, in the presence of other indigenous organisms, E. coli and enterococci were only sustained for 5 days at 26 °C. Pulsed-field gel electrophoresis (PFGE) analysis showed that the plant Enterococcus faecalis isolates were genetically distinct from the human isolates; identical PFGE patterns were observed among plant isolates that fell into one of six clonal groups. These findings suggest that (i) E. coli and enterococci occurrence in pitcher plants is rather common in the bog studied, although their originating source is unclear, and (ii) the pitcher fluid contains adequate nutrients, especially carbon and energy sources, to promote the growth of indicator bacteria; however, under natural conditions, the biotic factors (e.g., competition for nutrients) may restrict their growth.Key words: indicator bacteria, environmental occurrence, microcosm, pitcher plant fluid, temperate bog.

Statistical analyses: possible reasons for unreliability of source tracking efforts

Analyses for the presence of indicator organisms provide information on the microbiological quality of water. Indicator organisms recommended by the United States Environmental Protection Agency for monitoring the microbiological quality of water include Escherichia coli, a thermotolerant coliform found in the feces of warm-blooded animals. These bacteria can also be isolated from environmental sources such as the recreational and pristine waters of tropical rain forests in the absence of fecal contamination. In the present study, E. coli isolates were compared to E. coli K12 (ATCC 29425) by restriction fragment length polymorphism using pulsed-field gel electrophoresis. Theoretically, genomic DNA patterns generated by PFGE are highly specific for the different isolates of an organism and can be used to identify variability between environmental and fecal isolates. Our results indicate a different band pattern for almost every one of the E. coli isolates analyzed. Cluster analysis did not show any relations between isolates and their source of origin. Only the discriminant function analysis grouped the samples with the source of origin. The discrepancy observed between the cluster analysis and discriminant function analysis relies on their mathematical basis. Our validation analyses indicate the presence of an artifact (i.e., grouping of environmental versus fecal samples as a product of the statistical analyses used and not as a result of separation in terms of source of origin) in the classification results; therefore, the large genetic heterogeneity observed in these E. coli populations makes the grouping of isolates by source rather difficult, if not impossible.

Discrimination efficacy of fecal pollution detection in different aquatic habitats of a high-altitude tropical country, using presumptive coliforms, Escherichia coli, and Clostridium perfringens spores

The performance of rapid and practicable techniques that presumptively identify total coliforms (TC), fecal coliforms (FC), Escherichia coli, and Clostridium perfringens spores (CP) by testing them on a pollution gradient in differing aquatic habitats in a high-altitude tropical country was evaluated during a 12-month period. Site selection was based on high and low anthropogenic influence criteria of paired sites including six spring, six stream, and four lakeshore sites spread over central and eastern parts of Uganda. Unlike the chemophysical water quality, which was water source type dependent (i.e., spring, lake, or stream), fecal indicators were associated with the anthropogenic influence status of the respective sites. A total of 79% of the total variability, including all the determined four bacteriological and five chemophysical parameters, could be assigned to either a pollution, a habitat, or a metabolic activity component by principal-component analysis. Bacteriological indicators revealed significant correlations to the pollution component, reflecting that anthropogenic contamination gradients were followed. Discrimination sensitivity analysis revealed high ability of E. coli to differentiate between high and low levels of anthropogenic influence. CP also showed a reasonable level of discrimination, although FC and TC were found to have worse discrimination efficacy. Nonpoint influence by soil erosion could not be detected during the study period by correlation analysis, although a theoretical contamination potential existed, as investigated soils in the immediate surroundings often contained relevant concentrations of fecal indicators. The outcome of this study indicates that rapid techniques for presumptive E. coli and CP determination may be reliable for fecal pollution monitoring in high-altitude tropical developing countries such as those of Eastern Africa.

Monitoring marine recreational water quality using multiple microbial indicators in an urban tropical environment

The microbial water quality at two beaches, Hobie Beach and Crandon Beach, in Miami-Dade County, Florida, USA was measured using multiple microbial indicators for the purpose of evaluating correlations between microbes and for identifying possible sources of contamination. The indicator microbes chosen for this study (enterococci, Escherichia coli, fecal coliform, total coliform and C. perfringens) were evaluated through three different sampling efforts. These efforts included daily measurements at four locations during a wet season month and a dry season month, spatially intensive water sampling during low- and high-tide periods, and a sand sampling effort. Results indicated that concentrations did not vary in a consistent fashion between one indicator microbe and another. Daily water quality frequently exceeded guideline levels at Hobie Beach for all indicator microbes except for fecal coliform, which never exceeded the guideline. Except for total coliform, the concentrations of microbes did not change significantly between seasons in spite of the fact that the physical-chemical parameters (rainfall, temperature, pH, and salinity) changed significantly between the two monitoring periods. Spatially intense water sampling showed that the concentrations of microbes were significantly different with distance from the shoreline. The highest concentrations were observed at shoreline points and decreased at offshore points. Furthermore, the highest concentrations of indicator microbe concentrations were observed at high tide, when the wash zone area of the beach was submerged. Beach sands within the wash zone tested positive for all indicator microbes, thereby suggesting that this zone may serve as the source of indicator microbes. Ultimate sources of indicator microbes to this zone may include humans, animals, and possibly the survival and regrowth of indicator microbes due to the unique environmental conditions found within this zone. Overall, the results of this study indicated that the concentrations of indicator microbes do not necessarily correlate with one another. Exceedence of water quality guidelines, and thus the frequency of beach advisories, depends upon which indicator microbe is chosen.

A Pilot Study of Microbial Contamination of Subtropical Recreational Waters

Microbial water quality indicators are used to determine whether a water body is safe for recreational purposes. There have been concerns raised about the appropriate use of microbial indicators to regulate recreational uses of water bodies, in particular those located in tropical and sub-tropical environments. This prospective cohort pilot study evaluated the relationship between microbial water quality indicators and public health within two public beaches without known sewage discharge, but with historically high microbial levels for one beach, in subtropical Miami-Dade County (Florida). Monitoring was conducted in three phases: daily water monitoring, beach sand sampling, and spatially intense water sampling. An epidemiological questionnaire from a Los Angeles recreational beach-goer study was used to assess the self-reported swimming-related symptoms and exposures. There was no significant association between the number nor the type of reported symptoms and the different sampling months or beach sites, although persons who returned repeatedly to the beach were more likely to report symptoms. The number of indicator organisms correlated negatively with the frequency of symptoms reported by recreational beach goers. Results of the daily monitoring indicated that different indicators provided conflicting results concerning beach water quality.Larger epidemiologic studies with individual exposure monitoring are recommended to further evaluate these potentially important associations in subtropical recreational waters.

Occurrence of Escherichia coli and enterococci in Cladophora (Chlorophyta) in nearshore water and beach sand of Lake Michigan

Each summer, the nuisance green alga Cladophora (mostly Cladophora glomerata) amasses along Lake Michigan beaches, creating nearshore anoxia and unsightly, malodorous mats that can attract problem animals and detract from visitor enjoyment. Traditionally, elevated counts of Escherichia coli are presumed to indicate the presence of sewage, mostly derived from nearby point sources. The relationship between fecal indicator bacteria and Cladophora remains essentially unstudied. This investigation describes the local and regional density of Escherichia coli and enterococci in Cladophora mats along beaches in the four states (Wisconsin, Illinois, Indiana, and Michigan) bordering Lake Michigan. Samples of Cladophora strands collected from 10 beaches (n = 41) were assayed for concentrations of E. coli and enterococci during the summer of 2002. Both E. coli and enterococci were ubiquitous (up to 97% occurrence), with overall log mean densities (+/- standard errors) of 5.3 (+/- 4.8) and 4.8 (+/- 4.5) per g (dry weight). E. coli and enterococci were strongly correlated in southern Lake Michigan beaches (P < 0.001, R(2) = 0.73, n = 17) but not in northern beaches (P = 0.892, n = 16). Both E. coli and enterococci survived for over 6 months in sun-dried Cladophora mats stored at 4 degrees C; the residual bacteria in the dried alga readily grew upon rehydration. These findings suggest that Cladophora amassing along the beaches of Lake Michigan may be an important environmental source of indicator bacteria and call into question the reliability of E. coli and enterococci as indicators of water quality for freshwater recreational beaches.