Bacterial Indicators Of Faecal Contamination Research Articles

Comparative stability of assay results of enterococci measured by culture and qPCR over time in bathing beach waters

The diurnal presence of the culturable bacterial indicators of fecal contamination in the water environment has been shown to be highly variable over time due to natural die-off and injury from effects of sunlight and other environmental stressors. Molecular analytes of a quantitative polymerase chain reaction (qPCR) method for measuring fecal contamination degrade considerably slower than the alternative of culturable fecal indicator bacteria. The rapid qPCR method holds the promise of more timely notification decisions with respect to postings or closure being made on the basis of microbial water quality samples collected earlier on the same day. In the case of culture-based methods requiring a 24 h or longer incubation period, decisions must be based on samples collected no sooner than the previous day. To examine the effect of this lag in assay results, temporal stability of a molecular Enterococci target analyte with that of traditional culture-based cells is compared using data from USEPA studies conducted between 2003 and 2007 on seven freshwater and marine beaches that were impacted by publicly-owned treatment works. Generally, levels of the molecular indicator were more consistent throughout the day between 8:00 am and 3:00 pm. The difference in temporal consistency is even more pronounced when the 24-h lag in culture-based results is taken into account.

Occurrence of human e nterovirus in tropical fish and shellfish and their relationship with fecal indicator bacteria.

Aim:Human enteroviruses in fish and shellfish are a health concern worldwide. Human infections occur due to the consumption of raw or insufficiently cooked fish or shellfish. The objective of this study was to determine the occurrence of human enteric viruses belonging to Enterovirus (EV) group in seafood in Mumbai and to correlate their occurrence with the bacterial indicators of fecal contamination.Materials and Methods:Samples of fresh fish and shellfish collected from fish landing centers and retail fish markets were analyzed by virus concentration, nucleic acid extraction, and reverse transcription-polymerase chain reaction (RT-PCR). Bacterial indicators of fecal contamination were estimated by the most probable number technique. The relationship between the presence of virus and fecal indicators was determined by statistical analysis.Results:A total of 89 samples comprising of fish, shrimps, oysters, clams, and mussels were screened in this study. EV was detected in 32 (35.95%) samples, and all the virus-positive samples belonged to bivalve molluscan group. None of the finfish and crustacean shellfish samples was positive for the enteric viruses. Clams were found to be the most contaminated with 48.4% of the samples being positive for EV. The prevalence of enteric viruses in seafood samples showed a strong positive correlation with the bacteriological indicators of fecal contamination, suggesting that fecal coliform bacteria are good indicators of EVs in tropical seafood.Conclusion:The presence of EVs in seafood is a public health hazard. Increasing level of coastal water contamination from anthropogenic sources is the primary reason for the contamination of seafood with EVs. Continuous monitoring of coastal waters and seafood for enteric viruses will help to ensure the safety of fish and shellfish for human consumption.

Waterborne Norovirus outbreak at a seaside resort likely originating from municipal water distribution system failure.

In May 2016 a Norovirus (NoV) gastroenteritis outbreak involved a high school class visiting a seaside resort near Taormina (Mascali, Sicily). Twenty-four students and a teacher were affected and 17 of them showed symptoms on the second day of the journey, while the others got ill within the following 2 days. Symptoms included vomiting, diarrhoea and fever, and 12 students required hospitalisation. Stool samples tested positive for NoV genome by Real-Time polymerase chain reaction assay in all 25 symptomatic subjects. The GII.P2/GII.2 NoV genotype was linked to the outbreak by ORF1/ORF2 sequence analysis. The epidemiological features of the outbreak were consistent with food/waterborne followed by person-to-person and/or vomit transmission. Food consumed at a shared lunch on the first day of the trip was associated to illness and drinking un-bottled tap water was also considered as a risk factor. The analysis of water samples revealed the presence of bacterial indicators of faecal contamination in the water used in the resort as well as in other areas of the municipal water network, linking the NoV gastroenteritis outbreak to tap water pollution from sewage leakage. From a single water sample, an amplicon whose sequence corresponded to the capsid genotype recovered from patients could be obtained.

Assessment of commercially packaged water for faecal bacterial indicators in Kano metropolis and its environs

A total of 60 commercially packaged drinking water comprising of 48 sachet and 12 bottled water samples were randomly collected and tested for bacterial indicators of fecal contamination. Escherichia coli type 1, Streptococcus fecalis and Clostridium perfringes were used as indices to evaluate potability, using Presumptive and Differential Coliform Counts. The results obtained were analyzed using McCrady's Statistical Table of Probability to ascertain the Most Probable Number (MPN) of Coliform organisms per 100mls of the water. Of the 48 sachet water analyzed, 2 (4.2%) were positive for Presumptive Coliform Count (PCC) with the first and second water samples showing a count of 160 MPN/l00mls and 30MPN/100mls respectively. All the bottled water analyzed were negative for PCC. Since the need for consumption of packaged water cannot be underestimated, it is of great necessity that the waters are properly treated in order to meet the bacteriological Standards for Potable drinking water. Key words: Packaged water, Bacterial Indicator, Kano metropolis.

Domestic wastewater disinfection by combined treatment using multi-soil-layering system and sand filters (MSL–SF): A laboratory pilot study

This study aims to present the removal of bacterial indicators of fecal contamination and parasites in a combined treatment using a multi-soil-layering system with sand filters (MSL–SF). This experiment was carried out in a laboratory scale. The MSL pilot (height 65cm, width 36cm, depth 30cm) was composed of soil mixture layers (SML) and gravel layers that are arranged in a brick-layer like pattern. The soil mixture layers are composed of local sandy soil mixed with sawdust, metal iron and charcoal at the ratio of 70, 10, 10 and 10%, respectively, on a dry weight basis. The applied hydraulic loading rate (HLR) was 200Lm−2day−1. The experimental sand filter included three parallel similar sand columns (inside diameter 12.5cm, height 120cm). Each column was filled with 80cm of fine sand and 10cm of gravel in the top and the bottom of the filter. Three sand columns HLRs (100, 200 and 400Lm−2day−1) were compared. The obtained results indicated that the conceptual model based on the combination of the MSL method and sand filter (MSL–SF) showed very high efficiency in organic matter, nutrients, bacteria and the reduction of parasites. The high performances were noted in the low HLR. The main removal percentage of SS, BOD5, COD, TN and TP were respectively 99.73, 97.78, 98.40, 92.93 and 96.21% for the HLR-100. In addition, the Log10 removal for total coliforms, fecal coliforms and fecal streptococci were 4.46, 4.47 and 4.13 Log unit respectively. MSL-SF is capable of removing 100% of helminthes eggs. The MSL system is an efficient method, especially for organic matter and nutrients (N, P) removal. Sand filters have experimentally been proved to be useful for fecal indicators and the removal of parasites. Good operational stability and high contaminants removal efficiency of the combined systems were observed. Therefore, the combination of the MSL system and sand filter offer a good alternative option for agricultural wastewater reuse.

Preliminary assessment of small scale bacterial depuration of <i>Crassostrea gigas</i> and <i>Anadara</i> spp., Gulf of Nicoya, Costa Rica

Bivalve molluscs are sold without any sanitary control in Costa Rica, which represents a public health risk dueto the possible accumulation of pathogenic bacteria. Small scale bacterial depuration treatments were preliminarilyevaluated on Crassostrea gigas and Anadara spp. from the Gulf of Nicoya, Costa Rica, through the useof a recirculating system with UV irradiation. The levels of Escherichia coli in the water were determined usingthe MPN method. The MPN of E. coli and the presence of Salmonella spp., Vibrio parahaemolyticus and V. cholerae were determined in molluscs. Results confirm the effectiveness of the E. coli depuration system designin C. gigas and Anadara spp. The MPN of E. coli in the molluscs was reduced between 79% and 100% after 24h. None of the other types of bacteria were found in the samples analyzed. This is the first C. gigas depurationstudy in Costa Rica and the first report concerning UV depuration for bacterial indicators of fecal contaminationin Anadara spp. This research serves as a basis for the implementation and improvement of mollusc purification conditions in the country. It is recommended to monitor extraction and harvesting areas, as well as to implement the depuration of bivalve molluscs so that traditional producers can offer an innocuous product with added value.Los moluscos bivalvos son comercializados sin ningún control sanitario en Costa Rica; por tanto, representan un riesgo para la salud pública, debido a que pueden acumular bacterias patógenas. Se evaluaron preliminarmente tratamientos para la depuración bacteriana a pequeña escala de Crassostrea gigas y Anadara spp. en el Golfo de Nicoya, Costa Rica, utilizando un sistema recirculado e irradiado con luz UV. Los niveles de Escherichia coli en el agua se determinaron mediante el método del NMP. A los moluscos se les determinó el NMP de E. coli y la presencia de Salmonella spp., Vibrio parahaemolyticus y V. cholerae. Los resultados confirman la efectividad del diseño del sistema para la depuración de E. coli en C. gigas y Anadara spp. A las 24 h, el NMP de E. coli en los moluscos se redujo entre el 79% y el 100%. No se comprobó la presencia de las demás bacterias en las muestras analizadas. Este es el primer estudio sobre depuración de C. gigas en Costa Rica y el primer reporte de depuración con UV de indicadores bacterianos de contaminación fecal en Anadara spp. Este trabajo sirve de base para implementar y mejorar las condiciones de la depuración de moluscos en el país. Se recomienda monitorear las áreas de extracción y cultivo e implementar la depuración de los moluscos bivalvos para que los productores artesanales puedan ofrecer un producto inocuo y con valor agregado.

Evidence for Coexistence of Distinct Escherichia coli Populations in Various Aquatic Environments and Their Survival in Estuary Water

Escherichia coli, a commensal bacterium from the intestinal tracts of humans and vertebrate animals, has been used as one of two bacterial indicators of fecal contamination, along with intestinal enterococci, to monitor the microbiological quality of water. However, water environments are now recognized as a secondary habitat where some strains can survive. We investigated the survival of E. coli isolates collected from bodies of water in France exhibiting distinct profiles of contamination, defined according to the following criteria: vicinity of the point sources of contamination, land use, hydrology, and physicochemical characteristics of the receiving water. We selected 88 E. coli strains among a collection of 352 strains to carry out a microcosm experiment in filtered estuarine water for 14 days at 10°C. The relationship between the survival of E. coli strains and genotypic and phenotypic characteristics was analyzed. This work showed that distinct E. coli survival types, able to survive from between 7 and 14 days to less than 2 days, coexisted in the water. E. coli isolates that rapidly lost their culturability were more frequently isolated in water recently contaminated by fecal bacteria of human origin, and most were multiresistant to antibiotics and harbored several virulence factors. In contrast, persistent strains able to survive from 4 to 14 days were more often found in water with low levels of fecal bacteria, belonged mainly to the B1 phylogroup, often harbored only one virulence factor, kspE or ompT, and were able to grow at 7°C.

Quantitative real-time PCR of enteric viruses in influent and effluent samples from wastewater treatment plants in Italy.

The prevalence of enteric viruses in wastewater, the efficacy of wastewater treatments in eliminating such viruses, and potential health risks from their release into the environment or by recycling of treated wastewaters, are very important issues in environmental microbiology. In this study we performed a quantitative TaqMan real-time PCR (polymerase chain reaction) analysis of enteric viruses on samples of influents and effluents from 5 wastewater treatment plants in and around Rome. Three epidemiologically important, waterborne enteric viruses were analyzed: adenoviruses, enteroviruses and noroviruses (GI and GII) and compared to classical bacterial indicators of fecal contamination. The concentration of adenoviruses was the highest, in both raw and treated waters. Mean values in influents were ranked as follows: adenovirus > norovirus GI > norovirus GII > enterovirus. In effluents, the ranking was: adenovirus > norovirus GI > enterovirus > norovirus GII. Removal efficiencies ranged from 35% (enterovirus) to 78% (norovirus GI), while removal efficiency for bacterial indicators was up to 99%. Since molecular quantification does not necessarily indicate an actual threat to human health, we proceeded to evaluate the infectivity of enterovirus particles in treated effluents through integrated cell culture and real-time PCR. Infectivity assays detected live virions in treated water, pointing to potential public health risks through the release of these viruses into the environment. A better understanding of viral presence and resistance to sewage purification processes have the potential of contributing to the effective management of risks linked to the recycling of treated wastewater, and its discharge into the environment.

Pressure Monitoring and Characterization of External Sources of Contamination at the Site of the Payment Drinking Water Epidemiological Studies

The 1990s epidemiological studies by Payment and colleagues suggested that an increase in gastrointestinal illnesses observed in the population consuming tap water from a system meeting all water quality regulations might be associated with distribution system deficiencies. In the current study, the vulnerability of this distribution system to microbial intrusion was assessed by characterizing potential sources of contamination near pipelines and monitoring the frequency and magnitude of negative pressures. Bacterial indicators of fecal contamination were recovered more frequently in the water from flooded air-valve vaults than in the soil or water from pipe trenches. The level of fecal contamination in these various sources was more similar to levels from river water rather than wastewater. Because of its configuration, this distribution system is vulnerable to negative pressures when pressure values out of the treatment plant reach or drop below 172 kPa (25 psi), which occurred nine times during a monitoring period of 17 months. The results from this investigation suggest that this distribution system is vulnerable to contamination by intrusion. Comparison of the frequency of occurrence of negative pressure events and repair rates with data from other distribution systems suggests that the system studied by Payment and colleagues is not atypical.

Physicochemical water quality of the Mfoundi River watershed at Yaoundé, Cameroon, and its relevance to the distribution of bacterial indicators of faecal contamination

Water quality of the Mfoundi River and four of its tributaries was studied by assessing some physicochemical variables (temperature, pH, conductivity, chlorides, phosphates and nitrogen ammonia, dissolved oxygen and carbon dioxide, organic matter content and Biological Oxygen Demand) and their influence on the distribution of bacterial indicators of faecal contamination (total coliform, faecal coliform and faecal streptococci). For this, standard methods for the examination of physicochemical parameters in water were followed, and statistical analysis (Pearson correlations) used to establish any relationships between physicochemical and biological variables. Our results revealed that almost all of the examined physicochemical variables exceeded World Health Organization (WHO) guidelines for recreational water. This was in agreement with a previous microbiological study indicating that these waters were not safe for human use or primary contact according to water quality standards established by the WHO. Results of our correlation analysis suggested that physicochemical and biological variables interact in complicated ways reflecting the complex processes occurring in the natural environment. It was also concluded that pollution in the Mfoundi River watershed poses an increased risk of infection for users and there exists an urgent need to control dumping of wastewater into this watershed.

Phosphorus and carbohydrate limitation of fecal coliform and fecal enterococcus within tidal creek sediments

Aquatic sediments can be a significant reservoir of bacterial indicators of fecal contamination at levels higher than the waters above them. Several environmental factors have been identified that can enhance the role of sediments as a reservoir for enteric pathogens, including carbon and/or phosphorus availability. In order to investigate the influence of these and other environmental factors on sediment fecal bacteria populations, sediment samples were collected from a coastal watershed in southeastern North Carolina and analyzed for fecal coliform and fecal enterococcus using a modified membrane filtration technique. Measurements of sediment phosphorus, sediment carbohydrate, and environmental factors were made and relationships with bacteria concentrations were assessed. These observations were accompanied by an experimental laboratory manipulation of phosphorus and carbohydrate and their effects on sediment-associated fecal coliform and enterococcus. Field results suggested that sediment-associated indicator bacteria were not limited by sediment phosphorus or carbohydrate. Experimental results suggested that sediment-associated fecal bacteria were more frequently limited by bioavailable carbohydrate. Sediment phosphorus was limiting for fecal enterococcus only where sediment P was initially low (<31 μg P g−1). A strong positive response by sediment fecal coliform concentrations to recent (24 h) precipitation was evidence that stormwater runoff delivers fecal bacteria loadings that are only partly measurable by conventional water sampling schemes, and by driving sediment and sediment P-loading plays a significant role in enhancing aquatic sediments as reservoirs for fecal microbes.

Duplex Real Time PCR for the detection of hepatitis A virus in shellfish using Feline Calicivirus as a process control

The consumption of bivalve shellfish is a common cause of foodborne outbreaks of viral origin. The evaluation of the sanitary quality of these products, however, is still based on bacterial indicators of fecal contamination (Reg. (EC) No. 2073/2005 and No.1441/2007) even if it is known that they are not reliable indicators of viral contamination. In this study a duplex Real Time PCR method for quantitative detection of hepatitis A (HAV) in shellfish was developed. Feline Calicivirus (FCV) was used as a control for assessing the effectiveness of the concentration and extraction process and the ability to eliminate PCR inhibitors present in the food matrix. The specific primers and probes for detection of HAV and FCV, chosen respectively from the 5′-UTR region and in the ORF1 region, were labeled with two different dyes and detected simultaneously. The method was applied on spiked and non-spiked shellfish from a local market. The amplification of HAV in the presence of FCV showed good linearity ( R 2 = 0.994) and the sensitivity limit of the reaction was at least 5 × 10 2 TCID 50 g −1 of an hepatopancreas extract.

Assessment of Antibacterial Activity of Solanum surrattense Against Waterborne Pathogens Isolated from Surface Drinking Water of the Potohar Region in Pakistan

ABSTRACT People dwelling in different cities of the Potohar region, Pakistan, are mostly dependent on surface water for drinking and domestic use. In an attempt to make available potable, safe water, filtration plants were constructed along with dams in the Potohar region. Water samples from these filtration plants were collected and analyzed for total and faecal coliform bacteria as well as for total viable count. Results showed that bacterial indicators of faecal contamination were numerous and significantly greater than World Health Organization recommended guidelines. Accordingly, antibacterial activity of methanolic and aqueous extracts of different parts of Solanum surrattense were assessed in vitro against waterborne pathogens. Fruits exhibited more antibacterial activities at incubation at 37°C than shoots and roots, which showed lowest Minimum Inhibitory Concentration (MIC) and zones of inhibition. These results suggest that plants offer a great potential for purification of drinking water that needs to be explored further because fruit extract of the aforementioned plant can be of practical use against waterborne pathogens.

Tracking human faecal contamination in tropical reservoirs in Puerto Rico

Using a combination of chemical and microbiological (culture-dependent and -independent) approaches, sources of human faecal contamination were identified in two water reservoirs in Puerto Rico ‐ Guajataca and La Plata. Fluorescence from optical brighteners (OB) ‐ commonly found in laundry detergents ‐ was used as an indicator of contamination from septic systems and other household discharges. Traditional indicators of faecal contamination (e.g. Escherichia coli; faecal enterococci) were enumerated, and human faecal contamination was confirmed through detection of Bifidobacterium adolescentis utilizing polymerase chain reaction (PCR)-based analyses. For Guajataca Reservoir, four of 19 sampling sites (21%) were positive for the presence of B. adolescentis under baseflow conditions. The OB fluorescence data suggested that the most likely source for three of these sites was residential, whereas the source of contamination at the remaining site, although of human origin, was probably non-residential. B. adolescentis was present in 83% (19 of 23) of the sampling sites in La Plata. The La Plata sources were more difficult to identify because samples were taken under stormflow conditions, although the presence of OB fluorescence suggested a residential origin in a number of instances. OB fluorescence and traditional bacterial indicators of faecal contamination produced a number of false positive and negative findings for both reservoirs, pointing to the importance of understanding the limitations of these tools for tropical freshwater systems. The results of this study should be useful in developing a weight-of-evidence approach for the identification of potential sources and extent of human faecal contamination in similar tropical reservoirs, a necessary step in the development of management plans to reduce or eliminate these sources.

Screening and identification of unknown contaminants in water destined to human consumption: A case study

As a response to a recent emergency case of suspected deliberate contamination of bottled drinking water addressed to sensitive personalities, samples were submitted to our laboratory for investigation; an analytical framework for wide screening and identification of unknown hazardous chemicals and microbiological agents in water has been developed and experienced for the purpose. The proposed approach combines several physico-chemical (inverse-phase liquid chromatography with spectrophotometric or mass spectrometric detection, suppressed ion chromatography, inductively coupled plasma–optical emission spectrometry, gas chromatography with mass spectrometric detection), microbiological (defined substrate technology) and biological assays (viability and macromolecular synthesis of cultured cells), thus allowing the detection of different classes of contaminants (inorganic and organic compounds, metals, algal toxins, bacterial indicators of faecal contamination, enteric pathogens, staphylococci, actinomycetes) and their effects. The application of the developed strategy to the suspected samples did not highlight the presence of specific and considerable risks for human health although a few organoleptic and microbiological parameters were compromised and water was not suitable for human consumption. Therefore, we were able to classify this episode as a water contamination threat instead of confirming an incident. The proposed screening-confirmatory analytical scheme can be a valuable tool for obtaining conclusive and relatively rapid results in investigations concerning accidental or intentional contamination of drinking water.

Comparison and Verification of Bacterial Water Quality Indicator Measurement Methods Using Ambient Coastal Water Samples

More than 30 laboratories routinely monitor water along southern California's beaches for bacterial indicators of fecal contamination. Data from these efforts frequently are combined and compared even though three different methods (membrane filtration (MF), multiple tube fermentation (MTF), and chromogenic substrate (CS) methods) are used. To assess data comparability and quantify variability within method and across laboratories, 26 laboratories participated in an intercalibration exercise. Each laboratory processed three replicates from eight ambient water samples employing the method or methods they routinely use for water quality monitoring. Verification analyses also were conducted on a subset of wells from the CS analysis to confirm or exclude the presence of the target organism. Enterococci results were generally comparable across methods. Confirmation revealed a 9% false positive rate and a 4% false negative rate in the CS method for enterococci, though these errors were small in the context of within- and among-laboratory variability. Fecal coliforms also were comparable across all methods, though CS underestimated the other methods by about 10%, probably because it measures only E. coli, rather than the larger fecal coliform group measured by MF and MTF. CS overestimated total coliforms relative to the other methods by several fold and was found to have a 40% false positive rate in verification. Across-laboratory variability was small relative to within- and among-method variability, but only after data entry errors were corrected. One fifth of the laboratories committed data entry errors that were much larger than any method-related errors. These errors are particularly significant because these data were submitted in a test situation where laboratories were aware they would be under increased scrutiny. Under normal circumstances, it is unlikely that these errors would have been detected and managers would have been obliged to issue beach water quality warnings.

Bacterial indicators of faecal contamination of the Gangetic river system right at its source

Abstract Gangotri glacier is situated in the Uttaranchal, India between 30°56′N and 79°04′–79°15′ E. The Gangotri glacier around 30 km in length covering an area of 143 km2 flowing north–west, is the largest valley type glacier in the western Himalaya. Water samples from 21 different sites moving down stream from the glacier, which is the source of river Ganges, during winter, summer and monsoon seasons taken for the analysis of total viable count, total coliform count, faecal coliform count and faecal streptococci count, which are indicator organisms of faecal contamination. Total viable counts were found in the range of 2 × 102 to 40 × 102 ml−1 in winter, 7 × 102 to 40 × 102 ml−1 in summer and 2 × 102 to 40 × 102 ml−1 in monsoon. The range of MPN 100 ml−1 for total coliform was found 34–1600, 300–1600 and 40–1600, for faecal coliform, it was 2–500, 2–900, 2–900 and for faecal streptococci, it was 33–900, 40–900 and 40–1600 in winter, summer and monsoon, respectively. The overall objective of this work is to investigate the incidence of these indicator organisms, coliforms, faecal coliforms and faecal streptococci in runoff of the Gangotri glacier, western Himalaya, India.

Hygienic risk assessment by monitoring pathogens in municipal sewage

The purpose of this study was to monitor the levels of human enteric viruses and enteric protozoa and to relate their presence to the microbes used as hygienic quality indicators in domestic sewage from a small community in Finland during a period of one year. Genome-based sensitive detection methods for the pathogens selected (astro- and Norwalk-like viruses, Giardia and Cryptosporidium) have become available only recently and thus no earlier data was available. The effluent sewage is delivered into a river that serves as raw water for a larger town and the pathogens therefore constitute a health risk. The results showed that all the monitored pathogens could be detected, and that enteric viruses were present at considerable concentrations in sewage. High concentrations of astrovirus in raw sewage were observed during a diarrhea epidemic in the local day-care centre. The presence of viruses did not correlate with the monitored bacterial indicators of faecal contamination (coliforms, E. coli and enterococci) or with bacteriophages (somatic coliphages, F-specific RNA phages and B. fragilis phages). Giardia cysts and Cryptosporidium oocysts were detected from one sample (1/10) each.

Fates of bacteriophages and bacterial indicators in the Moselle river (France)

It has been suggested that bacteriophages can provide useful information about the pathogenic microorganisms, particularly enteric viruses, present in water. This information is complementary to that obtained from bacterial indicators of faecal contamination, which would be of great value for evaluating the risks associated with the use of certain types of water. Before bacteriophages can be used as indicators of faecal contamination, we need to confirm that bacteriophages give a different response to that given by the well-known bacteria indicators and to determine what happens to bacteriophages in river water. Indeed, drinking water is often produced from river water, either by natural filtration through the soil or after undergoing various treatments. We collected 96 river water samples from six different sites between February and November 2000. The samples were analysed for three faecal indicator bacteria (thermotolerant coliforms, enterococci and spores of sulphite-reducing anaerobes) and three types of bacteriophages (somatic coliphages, F-specific phages and Bacteroides fragilis phages). The densities of thermotolerant coliforms and enterococci depended mainly on physical factors such as flow rate and water temperature. High temperature and low flow rate led to a decrease in the density of these microorganisms, especially in the absence of a major input of faecal pollution. Conversely, the densities of somatic coliphages, F-specific phages and spores of sulphite-reducing anaerobes remained constant regardless of the flow rate and temperature. The density of Bacteroides fragilis phages was too low for unambiguous determination of their fate in river water.

Leaching of bacterial indicators of faecal contamination through four New Zealand soils

Land application of animal waste can result in bacterial contamination of shallow groundwater and/or waterways. Using 500-mm-diameter barrel lysimeters, we investigated the potential for bacterial indicators to leach through 4 New Zealand soils treated with dairy shed effluent (DSE). DSE was applied to soil lysimeters containing poorly drained Gley Soils (Te Kowhai and Netherton) and well-drained Allophanic (Waihou) and Pumice Soils (Atiamuri) at 50 mm/h, a typical field application rate used by farmers. Simulated rainfall was applied continuously at a rate of 5–10 mm/h, and leachate collected at a depth of 700 or 750 mm was analysed for faecal coliforms, Escherichia coli, and faecal enterococci. Bacterial indicators of faecal contamination readily moved through the Te Kowhai and Netherton soils, but not the Waihou and Atiamuri soils. Differential microbial movement was attributed to differences in soil structure. The poorly drained soils have coarse subsoil structures with macropores, favouring bypass flow. In contrast, the welldrained soils have a finer, more uniformly porous soil structure that minimised bypass flow and allowed matrix flow.