Occurrence, molecular characterization and antibiogram of water quality indicator bacteria in river water serving a water treatment plant

Water pollution by microorganisms of fecal origin is a current world-wide public health concern. Total coliforms, fecal coliforms (Escherichia coli) and enterococci are indicators commonly used to assess the microbiological safety of water resources. In this study, influent water samples and treated water were collected seasonally from a water treatment plant and two major water wells in a Black Belt county of Alabama and evaluated for water quality indicator bacteria. Influent river water samples serving the treatment plant were positive for total coliforms, fecal coliforms (E. coli), and enterococci. The highest number of total coliform most probable number (MPN) was observed in the winter (847.5 MPN/100 mL) and the lowest number in the summer (385.6 MPN/100 mL). Similarly E. coli MPN was substantially higher in the winter (62.25 MPN/100 mL). Seasonal variation of E. coli MPN in influent river water samples was strongly correlated with color (R² = 0.998) and turbidity (R² = 0.992). Neither E. coli nor other coliform type bacteria were detected in effluent potable water from the treatment plant. The MPN of enterococci was the highest in the fall and the lowest in the winter. Approximately 99.7 and 51.5 enterococci MPN/100 mL were recorded in fall and winter seasons respectively. One-way ANOVA tests revealed significant differences in seasonal variation of total coliforms (P < 0.05), fecal coliforms (P < 0.01) and enterococci (P < 0.01). Treated effluent river water samples and well water samples revealed no enterococci contamination. Representative coliform bacteria selected by differential screening on Coliscan Easygel were identified by 16S ribosomal RNA gene sequence analysis. E. coli isolates were sensitive to gentamicin, trimethoprim/sulfamethazole, ciprofloxacin, vancomycin, tetracycline, ampicillin, cefixime, and nitrofurantoin. Nonetheless, isolate BO-54 displayed decreased sensitivity compared to other E. coli isolates. Antibiotic sensitivity pattern can be employed in microbial source tracking.     

Microbiological quality of water from hand-dug wells used for domestic purposes in urban communities in Kumasi,Ghana

Assessment was done on the microbiological quality of water in hand-dug wells in urban communities in Kumasi, Ghana. A total of 256 water samples were taken from eight wells and examined for faecal coliforms, enterococci and helminths. High contamination levels were recorded in the wells, more so in the wet season, with faecal coliforms levels between 6.44 and 10.19 log units and faecal enterococci between 4.23 and 4.85 CFU per 100 ml. Influence on protection and lining of wells on water quality was not pronounced but mechanization reduced contamination significantly by about 3 log units. This study shows a stronger influence of poor sanitation and improper placement of wells on water quality compared to improvements made from lining and protection of wells. In the race to increase access to drinking water in poor urban settlements, quality of groundwater could be a major barrier, if provision of drinking water is not matched with improvements in sanitation and urban planning.     

Assessment of sources of human pathogens and fecal contamination in a Florida freshwater lake

We investigated the potential for a variety of environmental reservoirs to harbor or contribute fecal indicator bacteria (FIB), DNA markers of human fecal contamination, and human pathogens to a freshwater lake. We hypothesized that submerged aquatic vegetation (SAV), sediments, and stormwater act as reservoirs and/or provide inputs of FIB and human pathogens to this inland water. Analysis included microbial source tracking (MST) markers of sewage contamination (Enterococcus faecium esp gene, human-associated Bacteroides HF183, and human polyomaviruses), pathogens (Salmonella, Cryptosporidium, Giardia, and enteric viruses), and FIB (fecal coliforms, Escherichia coli, and enterococci). Bayesian analysis was used to assess relationships among microbial and physicochemical variables. FIB in the water were correlated with concentrations in SAV and sediment. Furthermore, the correlation of antecedent rainfall and major rain events with FIB concentrations and detection of human markers and pathogens points toward multiple reservoirs for microbial contaminants in this system. Although pathogens and human-source markers were detected in 55% and 21% of samples, respectively, markers rarely coincided with pathogen detection. Bayesian analysis revealed that low concentrations (<45 CFU × 100 ml⁻¹) of fecal coliforms were associated with 93% probability that pathogens would not be detected; furthermore the Bayes net model showed associations between elevated temperature and rainfall with fecal coliform and enterococci concentrations, but not E. coli. These data indicate that many under-studied matrices (e.g. SAV, sediment, stormwater) are important reservoirs for FIB and potentially human pathogens and demonstrate the usefulness of Bayes net analysis for water quality assessment.     

Rainwater harvesting, quality assessment and utilization in Kefalonia Island, Greece

The quality of harvested rainwater which is used for domestic and drinking purposes in the northern area of Kefalonia Island in SW Greece and the factors affecting it were assessed through 3-year surveillance. In 12 seasonal samplings, 156 rainwater and 144 ground- or mixed water samples were collected from ferroconcrete storage tanks (300-1000 m3 capacity), which are adjacent to cement-paved catchment areas (600-3000 m2). Common anions and major cations as well as the metals Fe, Mn, Cd, Pb, Cu, Cr, Ni and Zn were tested. The presence of three major groups of organic compounds, polycyclic aromatic hydrocarbons (PAHs), organochloride pesticides (OCPs) and volatile organic compounds (VOCs), was screened by common analytical techniques. All of the rainwater samples were within the guidelines for chemical parameters established by the 98/93/EU directive. As far as microbiological quality is concerned, total coliforms, Escherichia coli and enterococci were detected in 80.3%, 40.9% and 28.8% of the rainwater samples, respectively, although they were found in low concentrations. Chemical and microbiological parameters showed seasonal fluctuations. Principal component analysis revealed that microbiological parameters were affected mainly by the cleanness level of catchment areas, while chemical parameters were influenced by the sea proximity and human activities. Disinfection should be applied into the tanker trucks which distribute the water to the consumers and not into the big storage tanks in order to avoid by-products formation. Due to the lack of fluoride in rainwater samples, the consumers must become aware of the fact that the supplementation of this element is needed.     

Sustainable microbial water quality monitoring programme design using phage-lysis and multivariate techniques

Contamination of surface waters is a pervasive threat to human health, hence, the need to better understand the sources and spatio-temporal variations of contaminants within river catchments. River catchment managers are required to sustainably monitor and manage the quality of surface waters. Catchment managers therefore need cost-effective low-cost long-term sustainable water quality monitoring and management designs to proactively protect public health and aquatic ecosystems. Multivariate and phage-lysis techniques were used to investigate spatio-temporal variations of water quality, main polluting chemophysical and microbial parameters, faecal micro-organisms sources, and to establish ‘sentry’ sampling sites in the Ouse River catchment, southeast England, UK. 350 river water samples were analysed for fourteen chemophysical and microbial water quality parameters in conjunction with the novel human-specific phages of Bacteroides GB-124 (Bacteroides GB-124). Annual, autumn, spring, summer, and winter principal components (PCs) explained approximately 54%, 75%, 62%, 48%, and 60%, respectively, of the total variance present in the datasets. Significant loadings of Escherichia coli, intestinal enterococci, turbidity, and human-specific Bacteroides GB-124 were observed in all datasets. Cluster analysis successfully grouped sampling sites into five clusters. Importantly, multivariate and phage-lysis techniques were useful in determining the sources and spatial extent of water contamination in the catchment. Though human faecal contamination was significant during dry periods, the main source of contamination was non-human. Bacteroides GB-124 could potentially be used for catchment routine microbial water quality monitoring. For a cost-effective low-cost long-term sustainable water quality monitoring design, E. coli or intestinal enterococci, turbidity, and Bacteroides GB-124 should be monitored all-year round in this river catchment.     

Monitoring source water for microbial contamination: evaluation of water quality measures

Watershed management programs often rely on monitoring for a large number of water quality parameters to define contaminant issues. While coliforms have traditionally been used to identify microbial contamination, these indicators cannot discriminate among potential contaminant sources. Microbial source tracking (MST) can provide the missing link that implicates the sources of contamination. The objective of this study was to use a weight-of-evidence approach (land use analysis using GIS, sanitary surveys, traditional water quality monitoring, and MST targets) to identify sources of pollution within a watershed that contains a raw drinking water source. For the study watersheds, statistical analyses demonstrated that one measure each of particulate matter (turbidity, particle counts), organic matter (total organic carbon, dissolved organic carbon, UV(254) absorbance), and indicator organisms (fecal coliforms, enterococci) were adequate for characterizing water quality. While these traditional parameters were useful for assessing overall water quality, they were not intended to differentiate between microbial sources at different locations. In contrast, the MST targets utilized (Rhodococcus coprophilus, sorbitol-fermenting Bifidobacteria, and male-specific coliphages) pinpointed specific sources of microbial pollution. However, these targets could not be used for routine monitoring due to a high percentage of non-detects.     

Microbial indicators and pathogens: removal, relationships and predictive capabilities in water reclamation facilities

Four water reclamation facilities in north-eastern Spain were monitored over 2 years to determine the occurrence and concentrations of a set of microbial indicators (total coliforms, Escherichia coli, enterococci, spores of sulphite reducing clostridia, somatic coliphages, F-specific RNA phages, phages infecting Bacteroides fragilis strain RYC2056 and phages infecting Bacteroides tethaiotaomicron strain GA-17), and two selected pathogens (cytopathogenic enteroviruses and viable Cryptosporidium oocysts). The indicator (survival) and index (presence) functions of the various indicators tested were evaluated through the wastewater treatments. The inactivation pattern of all groups of bacteriophages tested was closer to the inactivation of enteroviruses than to the inactivation of the conventional bacterial indicators tested. The inactivation of sulfite reducing clostridia spores and bacteriophages more closely approximates the reduction of viable Cryptosporidium than do the conventional bacterial indicators. We observed neither index functions nor a predictive relationship between any of microbial indicators and viable Cryptosporidium oocysts. In contrast, several regression models (r > 0.6) and discriminant functions (67-88% well classified samples) based mostly on numbers of bacteriophages were able to predict both the presence and concentrations of enteroviruses. A combination of both bacterial and bacteriophage indicators seem to be the best choice for ensuring the microbial quality of reclaimed water.     

Contamination of potable roof-collected rainwater in Auckland, New Zealand

One-hundred and twenty-five domestic roof-collected rainwater supplies in four rural Auckland districts were investigated in a cross-sectional survey to determine water quality. Samples of cold faucet water were analysed for physico-chemical and microbiological determinands, including metals (zinc, copper and lead), bacterial indicator organisms--heterotrophic plate count (HPC), total coilforms (TC), faecal coliforms (FC), enterococci (ENT), bacterial pathogens including Salmonella spp., Legionella spp., Campylobacter spp., Aeromonas spp. and the protozoa, Cryptosporidium and Giardia. Twenty-two supplies (17.6%) exceeded one or more of the maximum acceptable values (MAV) or maximum guideline values for chemical determinands of the New Zealand Drinking Water Standards (NZDWS) and 70 (56.0%) supplies exceeded the microbiological criteria of < 1 FC/100 mL. Eighteen supplies (14.4%) exceeded the NZDWS MAV for lead of 0.01 mg/L and three (2.4%) exceeded that for copper, of 2 mg/L. Those supplies with lead or galvanised iron comprising part of the roof or collecting system were more likely to show lead contamination (p = 0.019) as were those supplies with a pH less than 7 (p = 0.013). The presence of the indicator organisms HPC, TC, FC and ENT were all significantly correlated with one another. Aeromonas spp. were identified in 20 (16.0%) supplies. There was a positive association between the presence of Aeromonas and the bacterial indicator organisms. Households reporting at least one member with gastrointestinal symptoms in the month prior to sampling, were more likely to have Aeromonas spp. identified in their water supply than those households without symptoms (odds ratio 3.22, 95% CI 1.15-9.01, p = 0.021). Salmonella typhimurium was detected in one of 115 (0.9%) supplies. Legionella spp. and Campylobacter spp. were not detected. There were 50 supplies sampled for protozoa (sampling criteria: > or = 30 FC or > or = 60 ENT). Cryptosporidium oocysts were detected in 2 (4%) of these. Giardia was not detected. This study demonstrates that roof-collected rainwater systems provide potable supplies of relatively poor physiochemical and microbiological quality in the Auckland area. Further research is required on Aeromonas spp. as potential indicators of both microbiological quality and health risk along with design and maintenance strategies to minimise contamination of potable roof-collected rainwater supplies.     

Seasonal relationships among indicator bacteria, pathogenic bacteria, Cryptosporidium oocysts, Giardia cysts, and hydrological indices for surface waters within an agricultural landscape

The South Nation River basin in eastern Ontario, Canada is characterized by mixed agriculture. Over 1600 water samples were collected on a bi-weekly basis from up to 24 discrete sampling sites on river tributaries of varying stream order within the river basin between 2004 and 2006. Water samples were analyzed for: densities of indicator bacteria (Escherichia coli, Clostridium perfringens, enterococci, total and fecal coliforms), the presence of pathogenic bacteria (Listeria monocytogenes, E. coli O157:H7, Salmonella spp., Campylobacter spp.), and densities of parasite Giardia cysts and Cryptosporidium oocysts. Relationships between indicator bacteria, pathogens, and parasite oocysts/cysts were overall weak, seasonally dependent, site specific, but primarily positive. However, L. monocytogenes was inversely related with indicator bacteria densities. Campylobacter, Salmonella, Giardia cysts and Cryptosporidium oocysts were most frequently detected in the fall. E. coli O157:H7 was detected at a very low frequency. Exploratory decision tree analyses found overall that E. coli densities were the most utilitarian classifiers of parasite/pathogen presence and absence, followed closely by fecal coliforms, and to a lesser extent enterococci and total coliforms. Indicator bacteria densities that classified pathogen presence and absence groupings, were all below 100 CFU per 100 mL⁻¹. Microorganism relationships with rainfall indices and tributary discharge variables were globally weak to modest, and generally inconsistent among season, site and microorganism. But, overall rainfall and discharge were primarily positively associated with indicator bacteria densities and pathogen detection. Instances where a pathogen was detected in the absence of a detectable bacterial indicator were extremely infrequent; thus, the fecal indicators were conservative surrogates for a variety of pathogenic microorganisms in this agricultural setting. The results from this study indicate that no one indicator or simple hydrological index is entirely suitable for all environmental systems and pathogens/parasites, even within a common geographic setting. These results place more firmly into context that robust prediction and/or indicator utility will require a more firm understanding of microorganism distribution in the landscape, the nature of host sources, and transport/environmental fate affinities among pathogens and indicators.     

Temporal flux and spatial dynamics of nutrients, fecal indicators, and zoonotic pathogens in anaerobic swine manure lagoon water

Confined animal feeding operations (CAFOs) often use anaerobic lagoons for manure treatment. In the USA, swine CAFO lagoon water is used for crop irrigation that is regulated by farm-specific nutrient management plans (NMPs). Implementation of stricter US environmental regulations in 2013 will set soil P limits; impacting land applications of manure and requiring revision of NMPs. Precise knowledge of lagoon water quality is needed for formulating NMPs, for understanding losses of N and C in ammonia and greenhouse gas emissions, and for understanding risks of environmental contamination by fecal bacteria, including zoonotic pathogens. In this study we determined year-round levels of nutrients and bacteria from swine CAFO lagoon water. Statistical analysis of data for pH, electrical conductivity (EC), inorganic and organic C, total N, water-soluble and total minerals (Ca, Cu, Fe, K, Mg, Mn, P, and Zn) and bacteria (Escherichia coli, enterococci, Clostridium perfringens, Campylobacter spp., Listeria spp., Salmonella spp., and staphylococci) showed that all differed significantly by dates of collection. During the irrigation season, levels of total N decreased by half and the N:P ratio changed from 9.7 to 2.8. Some seasonal differences were correlated with temperature. Total N and inorganic C increased below 19 °C, and decreased above 19 °C, consistent with summer increases in ammonia and greenhouse gas emissions. Water-soluble Cu, Fe, and Zn increased with higher summer temperatures while enterococci and zoonotic pathogens (Campylobacter, Listeria, and Salmonella) decreased. Although their populations changed seasonally, the zoonotic pathogens were present year-round. Increasing levels of E. coli were statistically correlated with increasing pH. Differences between depths were also found. Organic C, total nutrients (C, Ca, Cu, Fe, Mg, Mn, N, P, and Zn) and C. perfringens were higher in deeper samples, indicating stratification of these parameters. No statistical interactions were found between collection dates and depths.     

Inactivation mechanisms of bacterial pathogen indicators during electro-dewatering of activated sludge biosolids

Electro-dewatering is an energy-efficient technology in which an electric field can increase the dryness of biosolids from secondary wastewater treatment from 15% w/w to 30-50% w/w. Here, we address bacterial pathogen indicators inactivation (total coliforms, Escherichia coli and aerobic endospores) during electro-dewatering, investigating the roles of electrochemically generated oxidants, extreme pH, and high temperature (from Joule heating). Our results demonstrate that temperature is the primary factor affecting total coliforms and E. coli inactivation. First, several electro-dewatering cycles were used to increase sludge temperature to about 100 °C after 6 min, during which time the average pH decreased from 7 to 3.6 after 10 min. Total coliforms and E. coli MPNs reached their detection limits after 6 min (with 4-5 logs of inactivation for total coliforms and 3-4 logs for E. coli). In contrast, aerobic endospores were not inactivated under these conditions; rather, their germination appeared to be stimulated by 6-8 min of electro-dewatering. Second, the dewatering cake was separated into four horizontal layers. After 8 min of electro-dewatering, the pH in the top layers decreased to 3, whereas the pH in the bottom layers increased to 8. Inactivation of total coliforms and E. coli in the sludge cake was similar in all layers, increasing with time, suggesting that oxidants and extreme pH are secondary inactivation factors. Finally, electrodes were cooled to maintain a temperature less than 34 °C. Although pH decreased significantly after 12 min of electro-dewatering, there was no significant bacterial pathogen indicator inactivation at low temperature.     

Comparison of the microbiological and chemical characterization of harvested rainwater and reservoir water as alternative water resources

Rainwater harvesting (RWH) offers considerable potential as an alternative water supply. In this study, all of the harvested rainwater samples met the requirements for grey water but not for drinking water. In terms of microbiological parameters, total coliform (TC) and Escherichia coli (EC) were measured in 91.6% and 72%, respectively, of harvested rainwater samples at levels exceeding the guidelines for drinking water, consistent with rainfall events. In the case of the reservoir water samples, TC and EC were detected in 94.4% and 85.2%, respectively, of the samples at levels exceeding the guidelines for drinking water. Both indicators gradually increased in summer and fall. The highest median values of both TC and EC were detected during the fall. Chemical parameters such as common anions and major cations as well as metal ions in harvested rainwater were within the acceptable ranges for drinking water. By contrast, Al shows a notable increase to over 200 μg L^− 1 in the spring due to the intense periodic dust storms that can pass over the Gobi Desert in northern China. In terms of statistical analysis, the harvested rainwater quality showed that TC and EC exhibit high positive correlations with NO₃⁻ (ρ_TC = 0.786 and ρ_EC = 0.42) and PO₄⁻ (ρ_TC = 0.646 and ρ_EC = 0.653), which originally derive from catchment contamination, but strong negative correlations with Cl⁻ (ρ_TC = − 0.688 and ρ_EC = − 0.484) and Na⁺ (ρ_TC = − 0.469 and ρ_EC = − 0.418), which originate from seawater.     

Dilemma of roof rainwater quality: applications of physical and organic treatment methods in a water scarce region of Mekelle,Ethiopia

The public health field has built a body of literature showing health benefits from improvements in water quality. However, the connection between roof harvested rainwater and health is not well documented especially in developing countries. Understanding the application of locally available treatment methods provides insight into this problem. This paper reports on experimental investigations where rainwater collected from a typical domestic roof in Mekelle, Ethiopia was treated using Moringa stenopetala seed, sand filter and boiling. The quality of the raw and treated roof harvested rainwater were compared against the Ethiopian and World Health Organization drinking water standards to investigate its suitability as a supplement for potable water supply. The pollutants analysed were total coliforms and turbidity. A significant improvement of turbidity and total coliforms was observed. This implies that application of plant coagulant followed by filtration can sufficiently treat rainwater and can be used as a low-cost treatment option in water scarce areas.     

Investigation of bacterial removal during the filtration process in constructed wetlands

In this study, bacterial removal efficiencies of planted and unplanted subsurface vertical flow constructed wetlands are compared. Indicator organisms such as faecal coliforms (Escherichia coli, total coliforms) and enterococci, and a number of heterotrophic bacteria (heterotrophic plate counts) have been analysed from the influent and effluent of the constructed wetlands as well as at different depths (water and substrate samples). Furthermore dry matter content and total organic carbon (TOC) have been analysed and correlated. The investigated systems show a high removal rate for indicator organisms (a log removal rate of 2.85 for HPC, 4.35 for E. coli, 4.31 for total coliforms and 4.80 for enterococci was observed). In general no significant difference in the removal efficiency of planted and unplanted vertical flow beds could be measured. Only enterococci measured in the substrate samples of the main layer of the filter could a statistically significant difference be observed.     

The ecology of "fecal indicator" bacteria commonly found in pulp and paper mill water systems

Coliform bacteria have long been used to indicate fecal contamination of water and thus a health hazard. In this study, the in-mill water and external effluent treatment systems of seven typical Canadian pulp and paper mills were all shown to support the growth of numerous coliforms, especially Klebsiella Spp., Escherichia coli. Enterobacter spp., and Citrobacter spp. In all mills and most sampled locations, klebsiellas were the predominant coliforms. Although all but one of the mills had no sewage input and most disinfected their feed (input) water, all contained the most typical fecal indicator bacterium, E. coli. Many of the mill coliforms were classified as fecal coliforms by standard "MPN" and metabolic tests, but this was shown to be due to their thermotolerance, not their origin. Mill coliforms were shown not to be just simple transients from feedwater or furnish (wood), but to be continuously growing, especially in some of the primary clarifiers. Isolated mill coliforms grew very well on a sterilized raw combined mill effluent. The fecal streptococci (enterococci), alternative indicators of fecal health hazards, were common in all mills in the absence of sewage. Ten strains of E. coli isolated from four mills were all shown to be non-toxigenic strains of harmless serotypes. No salmonellas were found. Therefore, the use of total coliform, fecal coliform, enterococci, or E. coli counts as indicators of fecal contamination, and thus of health hazard in pulp and paper mill effluents or biosolids (sludges) known to be free of fecal input is invalid.     

Detection of the human specific Bacteroides genetic marker provides evidence of widespread sewage contamination of stormwater in the urban environment

Human sewage contamination of surface waters is a major human health concern. We found urban stormwater systems that collect and convey runoff from impervious surfaces act as a conduit for sewage originating from breeches in sanitary sewer infrastructure. A total of 828 samples at 45 stormwater outfalls were collected over a four-year period and assessed by culture based methods, PCR, and quantitative PCR (qPCR) to test for traditional and alternative indicators of fecal pollution. All outfalls had the HF183 (human) Bacteroides genetic marker detected in at least one sample, suggesting sewage contamination is nearly ubiquitous in the urban environment. However, most outfalls were intermittently positive, ranging from detection in 11%-100% of the samples. Positive results did not correlate with seasonality, rainfall amounts, or days since previous rainfall. Approximately two-thirds of the outfalls had high (>5000 copy number, i.e. CN, per 100 ml) or moderate levels (1000-5000 CN per 100 ml) of the human Bacteroides genetic marker. Escherichia coli (E. coli) and enterococci levels did not correlate to human Bacteroides. A total of 66% of all outfall samples had standard fecal indicator levels above 10,000 CFU per 100 ml. A tiered assessment using this benchmark to identify high priority sites would have failed to flag 35% of the samples that had evidence of sewage contamination. In addition, high fecal indicators would have flagged 33% of samples as priority that had low or no evidence of sewage. Enteric virus levels in one outfall with high levels of the human Bacteroides genetic marker were similar to untreated wastewater, which illustrates stormwater can serve as a pathway for pathogen contamination. The major source of fecal pollution at four of five river sites that receive stormwater discharge appeared to be from sewage sources rather than non-human sources based on the ratios of human Bacteroides to total Bacteroides spp. This study shows the feasibility and benefits of employing molecular methods to test for alternative indicators of fecal pollution to identify sewage sources and potential health risks and for prioritization of remediation efforts.     

The Microbiological Quality of Private Water Supplies

This paper provides a detailed assessment of the microbiological quality of a selection of private water supplies. Samples were taken from 91 supplies and analyzed for total coliforms, faecal coliforms and faecal streptococci. The microbiological quality of the samples was generally poor, with almost 50% of the supplies failing to meet the required standards on at least one occasion. Given the high level of sanitary microbiological failures, there is the possibility that harmful microorganisms could be present and a significant risk to health cannot be discounted.     

The Microbiological Quality of Private Water Supplies

This paper provides a detailed assessment of the microbiological quality of a selection of private water supplies. Samples were taken from 91 supplies and analyzed for total coliforms, faecal coliforms and faecal streptococci. The microbiological quality of the samples was generally poor, with almost 50% of the supplies failing to meet the required standards on at least one occasion. Given the high level of sanitary microbiological failures, there is the possibility that harmful microorganisms could be present and a significant risk to health cannot be discounted.     

Enterococcus and Escherichia coli fecal source apportionment with microbial source tracking genetic markers – Is it feasible?

Fecal pollution is measured in surface waters using culture-based measurements of enterococci and Escherichia coli bacteria. Source apportionment of these two fecal indicator bacteria is an urgent need for prioritizing remediation efforts and quantifying health risks associated with source-specific pathogens. There are a number of quantitative real-time PCR (QPCR) assays that estimate concentrations of source-associated genetic markers; however, their concentrations are not necessarily amenable to source apportionment because the markers may differ in prevalence across sources. Here we mathematically derive and test, under ideal conditions, a method that utilizes the ratios of fecal source-associated genetic markers and culture and molecular measurements of general fecal indicators to apportion enterococci and E. coli. The source contribution is approximately equal to the ratio of the source-associated and the general fecal indicator concentrations in a water sample divided by their ratio in the source material, so long as cross-reactivity is negligible. We illustrate the utility of the ratio method using samples consisting of mixtures of various fecal pollution sources. The results from the ratio method correlated well with the actual source apportionment in artificial samples. However, aging of contamination can confound source allocation predictions. In particular, culturable enterococci and E. coli, the organisms presently regulated in the United States and much of the world, decay at different rates compared to source-associated markers and as a result cannot be apportioned using this method. However, limited data suggest a similar decay rate between source-associated and QPCR-measured Enterococcus and E. coli genetic markers, indicating that apportionment may be possible for these organisms; however further work is needed to confirm.     

Risk factors contributing to microbiological contamination of shallow groundwater in Kampala,Uganda

A study of water quality variation in shallow protected springs in Kampala was undertaken over a 12-month period to assess the causes of microbiological contamination. The microbiological quality of water was assessed using thermotolerant coliforms and faecal streptococci. Sanitary inspections and hazard assessments were undertaken to identify faecal sources (hazards), contaminant pathways and contributory factors. Data were collected on rainfall and population as additional factors potentially exerting an influence on microbiological quality. Initial analysis of the data showed a significant relationship between median level of contamination and rainfall, in particular to short-term rainfall events. Total sanitary risk score showed a significant relationship with median level of contamination, but population density may be a confounding factor. The raw microbiological data were transformed into five water quality targets: <1 and < or =10 cfu 100ml(-1) for faecal streptococci; and <1, < or =10 and < or=50 cfu 100 ml(-1) for thermotolerant coliforms. The presence of individual risk factors as well as variables for rainfall and population density were analysed with respect to failure to meet these water quality targets using contingency tables. Logistic regression models were developed for each of the five water quality targets. The analysis strongly suggested that there is rapid recharge of the springs after rainfall and this leads to microbiological contamination. On-site sanitation was less important than other sources of faecal matter, which was consistent with a low sanitation coverage in the study area. The study suggested that improving sanitary completion and local environmental hygiene was more important than controlling on-site sanitation in improving the quality of these springs.