Comparing the partitioning behavior of Giardia and Cryptosporidium with that of indicator organisms in stormwater runoff

Microbial association with particles can significantly affect the fate and transport characteristics of microbes in aquatic systems as particle-associated organisms will be less mobile in the environment than their free phase (i.e. unattached) counterparts. As such, similarities or dissimilarities in the partitioning behavior of indicator organisms and pathogens may have an impact on the suitability of a particular indicator to act as a surrogate for a pathogen. This research analyzed the partitioning behavior of two pathogens (Cryptosporidium, Giardia) and several common indicator organisms (fecal coliform, Escherichia coli, Enterococci, Clostridium perfringens spores, and coliphage) in natural waters under both dry and wet weather conditions. Samples were taken from several streams in two distinct sampling phases: (i) single grab samples; and (ii) intrastorm samples obtained throughout the duration of four storms. Partitioning behavior varied by microbial type, with 15-30% of bacterial indicators (fecal coliform, E. coli, and Enterococci) associated with settleable particles compared to 50% for C. perfringens spores. Both pathogens exhibited similar levels of particle association during dry weather (roughly 30%), with increased levels observed during wet weather events (Giardia to 60% and Cryptosporidium to 40%). The settling velocities of particle-associated microbes were also estimated, with those of the bacterial indicators (fecal coliform, E. coli, and Enterococci), as well as C. perfringens spores, being similar to that of the Giardia and Cryptosporidium, suggesting these organisms may exhibit similar transport behavior. With respect to intrastorm analysis, the highest microbial concentrations, in both particle-associated and free phase, occurred during the earlier stages of a storm. The total loadings of both indicators and pathogens were also estimated over the course of individual storms.     

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.     

Contribution of treated wastewater to the microbiological quality of Seine River in Paris

Urban part of Seine River serving as drinking water supply in Paris can be heavily contaminated by Cryptosporidium spp. and Giardia duodenalis. In the absence of agricultural practice in this highly urbanized area, we investigated herein the contribution of treated wastewater to the microbiological quality of this river focusing on these two parasites. Other microorganisms such as faecal bacterial indicators, enteroviruses and oocysts of Toxoplasma gondii were assessed concurrently. Raw wastewaters were heavily contaminated by Cryptosporidium and Giardia (oo)cysts, whereas concentrations of both protozoa in treated wastewater were lower. Treated wastewater, flowed into Seine River, had a parasite concentration closed to the one found along the river, in particular at the entry of a drinking water plant (DWP). Even if faecal bacteria were reliable indicators of a reduction in parasite concentrations during the wastewater treatment, they were not correlated to protozoal contamination of wastewater and river water. Oocysts of T. gondii were not found in both raw and treated wastewater, or in Seine River. Parasitic contamination was shown to be constant in the Seine River up to 40 km upstream Paris. Altogether, these results strongly suggest that treated wastewater does not contribute to the main parasitic contamination of the Seine River usually observed in this urbanized area.     

Quantification of pathogenic microorganisms and microbial indicators in three wastewater reclamation and managed aquifer recharge facilities in Europe

Managed Aquifer Recharge (MAR) is becoming an attractive option for water storage in water reuse processes as it provides an additional treatment barrier to improve recharged water quality and buffers seasonal variations of water supply and demand. To achieve a better understanding about the level of pathogenic microorganisms and their relation with microbial indicators in these systems, five waterborne pathogens and four microbial indicators were monitored over one year in three European MAR sites operated with reclaimed wastewater. Giardia and Cryptosporidium (oo)cysts were found in 63.2 and 36.7% of the samples respectively. Salmonella spp. and helminth eggs were more rarely detected (16.3% and 12.5% of the samples respectively) and Campylobacter cells were only found in 2% of samples. At the Belgian site advanced tertiary treatment technology prior to soil aquifer treatment (SAT) produced effluent of drinking water quality, with no presence of the analysed pathogens. At the Spanish and Italian sites amelioration of microbiological water quality was observed between the MAR injectant and the recovered water. In particular Giardia levels decreased from 0.24-6.14 cysts/L to 0-0.01 cysts/L and from 0.4-6.2 cysts/L to 0-0.07 cysts/L in the Spanish and Italian sites respectively. Salmonella gene copies and Giardia cysts were however found in the water for final use and/or the recovered groundwater water at the two sites. Significant positive Spearman correlations (p < 0.05, r_s range: 0.45-0.95) were obtained, in all the three sites, between Giardia cysts and the most resistant microbial markers, Clostridium spores and bacteriophages.     

Occurrence and levels of indicator bacteriophages in bathing waters throughout Europe

Somatic coliphages, F-specific RNA bacteriophages, bacteriophages infecting Bacteroides fragilis, Escherichia coli and enterococci were counted in bathing waters in the late spring and summer. We tested fresh and marine bathing waters from North, South, East and West Europe expected to contain between 100 and 500 E. coli per 100 ml, although wider ranges were sometimes found. Bacteriophages were counted after concentration, since a preliminary study proved that this step was necessary to obtain positive counts. During monitoring, a first-line quality control with reference materials for bacteria and bacteriophages was performed by all the laboratories participating in the study. The same microbes were also counted in raw sewage samples from various areas in Europe, where the bacterial indicators and the three groups of bacteriophages were detected in roughly the same numbers. All groups of bacteriophages were detected in both fresh and marine bathing waters throughout Europe. Reliable and complete results from 147 samples showed that for log-transformed values, E. coli and bacteriophages were slightly correlated. However, the slope of the regression line changed according to E. coli concentration and the correlation diminished when this concentration was close to zero per 100 ml. The ratios between E. coli and phages in bathing waters differed significantly from those in sewage. The relative amounts of bacteriophages, mainly somatic coliphages and phages infecting Bact. fragilis RYC2056, increased in bathing waters with low E. coli concentration, especially in seawater samples containing <100 E. coli per 100 ml. The relationship of bacteriophages with respect to enterococci paralleled that of bacteriophages with respect to E. coli. Somatic coliphages and bacteriophages infecting Bact. fragilis are useful to predict the presence of some pathogens with the same origin as present bacterial indicators but with higher survival rates.     

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.     

Intensive exploitation of a karst aquifer leads to Cryptosporidium water supply contamination

Groundwater from karst aquifers is an important source of drinking water worldwide. Outbreaks of cryptosporidiosis linked to surface water and treated public water are regularly reported. Cryptosporidium oocysts are resistant to conventional drinking water disinfectants and are a major concern for the water industry. Here, we examined conditions associated with oocyst transport along a karstic hydrosystem, and the impact of intensive exploitation on Cryptosporidium oocyst contamination of the water supply. We studied a well-characterized karstic hydrosystem composed of a sinkhole, a spring and a wellbore. Thirty-six surface water and groundwater samples were analyzed for suspended particulate matter, turbidity, electrical conductivity, and Cryptosporidium and Giardia (oo)cyst concentrations. (Oo)cysts were identified and counted by means of solid-phase cytometry (ChemScan RDI^®), a highly sensitive method. Cryptosporidium oocysts were detected in 78% of both surface water and groundwater samples, while Giardia cysts were found in respectively 22% and 8% of surface water and groundwater samples. Mean Cryptosporidium oocyst concentrations were 29, 13 and 4/100 L at the sinkhole, spring and wellbore, respectively. Cryptosporidium oocysts were transported from the sinkhole to the spring and the wellbore, with respective release rates of 45% and 14%, suggesting that oocysts are subject to storage and remobilization in karst conduits. Principal components analysis showed that Cryptosporidium oocyst concentrations depended on variations in hydrological forcing factors. All water samples collected during intensive exploitation contained oocysts. Control of Cryptosporidium oocyst contamination during intensive exploitation is therefore necessary to ensure drinking water quality.     

Cryptosporidium spp. and Giardia duodenalis in two areas of Galicia (NW Spain)

The aim of the present study was to investigate the environmental dispersal of Cryptosporidium spp. and Giardia duodenalis in two distinct areas (coastal and inland) in Galicia (NW Spain). Faecal samples were collected from healthy asymptomatic domestic (cows and sheep) and wild animals (deer and wild boars) in the selected areas. In each of the selected areas, samples of untreated water (influent) and of treated water (final effluent) were collected from each of the 12 drinking water treatments plants (DWTPs) and 12 wastewater treatment plants (WTPs) under study. Analysis of a single sample from each of the 635 (coastal) and 851 (inland) domestic and wild animals selected at random revealed that the prevalences of cryptosporidiosis and giardiosis in coastal area were 9.2% and 15.9% respectively, and in inland area, 13.7% and 26.7% respectively. In the coastal area, Cryptosporidium spp. oocysts were detected in influent and effluent samples from 2/12 (16.6%) DWTPs and 8/12 (66.6%) WTPs, while G. duodenalis cysts were detected in influent and effluent samples from 3/12 (25.0%) DWTPs and 12/12 (100%) WTPs. The concentrations were notably higher in WTPs; the mean parasite concentrations in the final treated effluent were 10 oocysts per litre and 137.8 cysts per litre for Cryptosporidium and Giardia, respectively. The mean concentration of G. duodenalis cysts per litre was significantly higher (P < 0.05) than the mean concentration of Cryptosporidium spp. oocysts per litre in both the influent and the effluent samples from all the treatment plants. In the coastal area, C. parvum, C. hominis and G. duodenalis assemblages A (I and II) and E were most repeatedly detected. In the inland area, C. parvum, C. andersoni and G. duodenalis assemblages A (I and II), B and E were most frequently identified.     

The assessment of particle association and UV disinfection of wastewater using indigenous spore-forming bacteria

Studies have shown that association between particles and coliform bacteria in wastewater influence the inactivation of these microorganisms by ultraviolet (UV) irradiation. This research investigated the potential use of indigenous aerobic spore-forming (ASF) bacteria for studying the particle - microorganism interaction and its effect on UV disinfection of protozoan pathogens, such as Giardia spp. and Cryptosporidium spp., present in effluents from full-scale municipal wastewater treatment plants. The effect of particle - ASF association was determined by homogenizing wastewater effluent samples before and after exposure to controlled UV doses delivered by a bench-scale collimated beam apparatus. Particle association between Bacillus subtilis spores added to wastewater and wastewater particles was also assessed. The results indicate that spores are not significantly associated with wastewater particulate matter and particle association does not significantly affect the inactivation of indigenous spores present in wastewater by UV radiation in this study.     

Ecotoxicological assessment of pulsed ultraviolet light‐treated water containing microbial species and Cryptosporidium parvum using a microbiotest test battery

Development of a pulsed ultraviolet (PUV) light system as an alternative disinfection method for water treatment has been investigated, yet little is known about the impact of applying such emerging technologies on the natural aquatic environment. This study reports on the use of a battery of ecotoxicological tests representative of different ecological trophic levels to determine the safety and potability of PUV‐treated water containing known pathogens. Water samples containing Cryptosporidium oocysts and Escherichia coli were treated with PUV light, and the ecotoxicological safety was determined by assessing toxicity in a range of representative microbiotests and the Rainbow Trout Hepatocyte (RTH)‐149 fish cell line. Results show that PUV rapidly inactivated Cryptosporidium and the selected microbial species; greater rates of inactivation were observed at higher ultraviolet doses. PUV‐treated samples did not elicit ecotoxicological effects in the trophic levels studied. This study highlights that PUV is an effective means of disinfecting water containing pathogens such as Cryptosporidium.     

The burden of drinking water-associated cryptosporidiosis in China: the large contribution of the immunodeficient population identified by quantitative microbial risk assessment

A comprehensive quantitative microbial risk assessment (QMRA) of Cryptosporidium infection, considering pathogen removal efficiency, different exposure pathways and different susceptible subpopulations, was performed based on the result of a survey of source water from 66 waterworks in 33 major cities across China. The Cryptosporidium concentrations in source water were 0-6 oocysts/10 L, with a mean value of 0.7 oocysts/10 L. The annual diarrhea morbidity caused by Cryptosporidium in drinking water was estimated to be 2701 (95% confidence interval (CI): 138-9381) cases per 100,000 immunodeficient persons and 148 (95% CI: 1-603) cases per 100,000 immunocompetent persons, giving an overall rate of 149.0 (95% CI: 1.3-606.4) cases per 100,000 population. The cryptosporidiosis burden associated with drinking water treated with the conventional process was calculated to be 8.31 × 10⁻⁶ (95% CI: 0.34-30.93 × 10⁻⁶) disability-adjusted life years (DALYs) per person per year, which was higher than the reference risk level suggested by the World Health Organization (WHO), but lower than that suggested by the United States Environmental Protection Agency (USEPA). Sixty-six percent of the total health burden due to cryptosporidiosis that occurred in the immunodeficient subpopulation, and 90% of the total DALYs was attributed to adults aged 15-59 years. The sensitivity analysis highlighted the great importance of stability of the treatment process and the importance of watershed protection. The results of this study will be useful in better evaluating and reducing the burden of Cryptosporidium infection.     

Comparative disinfection of treated sewage with chlorine and ozone: Effect of nitrification

Chlorine and ozone were compared in pilot plants (capacity about 3.2 m³ h⁻¹), which were fed with the same activated sludge treated and filtered water. Together with physico-chemical analysis the water was analysed for different types of microorganisms, including vegetative bacteria (total and thermotolerant coliforms, faecal streptococci and Pseudomonas aeruginosa), bacterial spores (spores of aerobic bacteria at 37°C and sulphite reducing clostridia) and bacterial viruses (somatic coliphages and F-specific bacteriophages).The average chlorine and ozone dose were, respectively, 3.65 and 15.3 mg l⁻¹ of water, while after a contact time for both of about 25 min the average residual concentrations were 1.79 and 0.35 mg l⁻¹ of water. These residuals were measured with the DPD-method. The ammonia-N concentration varied greatly (0.06–72.0 mg l⁻¹) and was used to group the data into four classes: (1) non-nitrified water, defined as water in which nitrate-N was smaller than ammonia-N; (2) moderately nitrified water, in which nitrate-N was larger than ammonia-N and the ammonia-N was higher than 2 mg l⁻¹; (3) well nitrified water, defined as water in which ammonia-N was lower than 2 mg l⁻¹; (4) very well nitrified water, in which ammonia-N was smaller than 0.5 mg l⁻¹.This classification indicated that the concentrations of most other impurities decreased with a better nitrification. Statistical analysis of the data showed also that ozone was a better disinfectant than chlorine in the case where the disinfection is based upon their residual content. The degree of nitrification had a greater effect on chlorine disinfection than on ozone disinfection.During chlorination the total residual chlorine decreased, with better nitrification; the chlorine demand increased; the composition of the residual chlorine changed very much and the inactivation of bacterial viruses improved. The vegetative bacteria showed a varying pattern; most were inactivated in moderately nitrified water, when the dichloramine concentration was highest and false positive FAC concentration was lowest of the four classes. Reduction of bacterial spores was not observed.During ozonization other effects were indicated. Reductions of most organims increased slightly with better nitrification; only reductions of F-specific bacteriophages decreased. There was also a small decrease of bacterial spores. The treated effluent had a high ozone consumption and the inactivation of the organisms was low in relation to ozone dose and residual ozone.The bromide concentration (0.3–2.9 mg l⁻¹) effected the chemistry of chlorine and ozone and had a positive effect on chlorine and ozone disinfection of total coliforms.For most types of micoorganisms the disinfection coefficients of the Selleck model and the germicidal efficiencies could be determined.     

Responses of soil microbial communities to weak electric fields

Electrokinetically stimulated bioremediation of soils (electro-bioremediation) requires that the application of weak electric fields has no negative effect on the contaminant degrading microbial communities. This study evaluated the hypothesis that weak direct electric current (DC) fields per se do not negatively influence the physiology and composition of soil microbial communities given that secondary electrokinetic phenomena such as soil pH changes and temperatures are minimized. Mildly buffered, water-saturated laboratory mesocosms with agricultural soil were subjected for 34 days to a constant electric field (X = 1.4 V cm^− 1; J ≈ 1.0 mA cm^− 2) and the spatiotemporal changes of soil microbial communities assessed by fingerprints of phospholipids fatty acids (PLFA) and terminal restriction fragment length polymorphisms (T-RFLP) of bacterial 16S rRNA genes. DC-induced electrolysis of the pore water led to pH changes (< 1.5 pH units) in the immediate vicinity of the electrodes and concomitant distinct soil microbial community changes. By contrast, DC-treated bulk soil distant to the electrodes showed no pH changes and developed similar PLFA- and T-RFLP-fingerprints as control soil in the absence of DC. Our data suggest that the presence of an electric field, if suitably applied, will not influence the composition and physiology of soil microbial communities and hence not affect their potential to biodegrade contaminants.     

The detection of Cryptosporidium oocysts and Giardia cysts in cistern water in the U.S. Virgin Islands

Most homes and public facilities in the U.S. Virgin Islands use a roof catchment system to obtain drinking water. Because water is so scarce throughout the islands, every building (except those federally owned) are required to have a cistern. Rainwater is collected in the cisterns and is subject to contamination from enteric pathogens found in the environment. The objective of this study was to determine the occurrence and concentrations of human enteric protozoa in cisterns originating from animal fecal contamination. Volumes of 400 1 of water were filtered from nine private and four public cisterns four times over a 1-year period for a total of 44 samples. After processing the filter, the entire volume was examined using Cryptosporidium and Giardia specific antibodies and epifluorescence microscopy to determine levels of Cryptosporidium oocysts and Giardia cysts. One or both of the protozoa were found in 81% of the public cisterns and this was statistically significant (P = 0.005) when compared to the private cisterns where 47% of the samples were positive. Cryptosporidium was found statistically more often in the 44 samples than Giardia. In addition, the use of a polyclonal antibody for Cryptosporidium which is genera-specific, also detected oocysts statistically more often than a monoclonal antibody which was more species-restrictive to C. parvum, which is associated with disease in humans, suggesting that non-mammalian oocysts were found more frequently in cistern waters. Levels ranged from 1 to 10 organisms/100 1 with one sample at 70 oocysts. These levels are associated with estimated daily risks of 10⁻² to 10⁻⁴ and are well above acceptable guidance as described for safe drinking water in the United States. On occasion high levels of heterotrophic bacteria (9.9 × 10⁵ CFU/ml) and total coliforms (> 2000 CFU/100 ml) were also detected in these waters. A statistically significant correlation was found between the detection of Cryptosporidium spp. and Giardia spp. (r = 0.47853, P = 0.0008). The results of this study show that Cryptosporidium and Giardia, as well as bacteria, are present in these waters at levels which may involve significant public health risks. Public cistern systems are of particular concern because of the high percentage which were contaminated and the greater number of people exposed.     

Removal efficiencies and attachment coefficients for Cryptosporidium in sandy alluvial riverbank sediment

Riverbank filtration has been shown to be effective for removing viable Cryptosporidium parvum oocysts. Drinking water systems that employ riverbank filtration may receive additional treatment credits beyond that which they can obtain using traditional engineering approaches. In order to develop guidance for removal effectiveness, screening level predictive modeling by colloid filtration theory combined with advection and dispersion modeling is potentially useful. Currently, only few studies have measured basic effective colloid filtration parameters for Cryptosporidium oocysts with naturally occurring riverbank sediments. In the focus of this study we conducted flow column experiments in triplicate and measured effective attachment rate coefficients for sandy river sediments of the Southern Great Plains which are low in organic matter. We found that for sediment sampled from these high-energy rivers there was no apparent dependency of C. parvum removal with carbon content, bacterial colony forming units, or with gross texture properties of the sands. The differences in particle size distribution for the sediments suggested that straining did not play a role in removal efficiency. First-order colloid attachment rate coefficients followed lognormal distribution functions. The coefficients also appeared to be unrelated to the differences in particle size distributions of the sediments, bacterial counts, or levels of total carbon or total organic carbon. Using Monte Carlo analyses, the lowest observed 5th percentile was 8.0 × 10⁻⁶ min⁻¹ and the highest observed 95th percentile was 1.6 × 10⁻³. Total log₁₀ removals ranged from 23 to 200 m⁻¹. These results have application for screening level colloid filtration modeling of riverbank filtration in these systems.     

Detection of Cryptosporidium spp. and Giardia duodenalis in surface water: A health risk for humans and animals

The objective of the present study was to determine the degree of contamination by Cryptosporidium spp. and Giardia duodenalis in a river basin in a livestock farming area in Galicia (NW, Spain). Water samples (50 l) were collected at 22 points in the main basin (including 5 recreational areas), and at the source and mouth of the 3 most important rivers and at the mouth of a smaller, secondary river. Faecal samples were collected from dairy cattle selected at random from 18 herds farmed in the area. A total of 139 neonatal calves, 480 heifers and 697 cows were sampled. The prevalence, intensity of infection and the risk associated with the spread of infection by both enteropathogens were determined. Water and faecal samples were collected in spring, summer, autumn and winter of 2007. The species and genotypes of these parasites present in the water samples were identified. In both water and faecal samples, more parasitic stages were collected in spring and summer than in autumn and winter. In spring, Cryptosporidium spp. oocysts were detected in 33 (9.4%) cows from 13 (72.2%) herds, and G. duodenalis cysts were detected in 56 (16.0%) cows from 15 farms (83.3%); the intensity of infection ranged from 5 to 7895 G. duodenalis cysts per gram of faeces. Infective stages of Cryptosporidium spp. and G. duodenalis were also detected in respectively 26 (89.6%) and 27 (93.1%) water samples, in spring. The mean concentrations of parasites ranged from 2 to 1200 Cryptosporidium spp. oocysts per litre and from 2 to 400 G. duodenalis cysts per litre. Cryptosporidium parvum, C. andersoni, C. hominis and assemblages A-I, A-II, E of G. duodenalis were detected. The presence of both protozoans must be monitored in cattle, in sources of water used for recreational purposes and in artificial waterways used by farmers (water channels, animal drinking water and drainage systems).     

Specificity and sensitivity evaluation of novel and existing Bacteroidales and Bifidobacteria-specific PCR assays on feces and sewage samples and their application for microbial source tracking in Ireland

Three novel ruminant-specific PCR assays, an existing ruminant-specific PCR assay and five existing human-specific PCR assays, which target 16S rDNA from Bacteroidales or Bifidobacteria, were evaluated. The assays were tested on DNA extracted from ruminant (n = 74), human (n = 59) and non-ruminant animal (n = 44) sewage/fecal samples collected in Ireland. The three novel PCR assays compared favourably to the existing ruminant-specific assay, exhibiting sensitivities of 91-100% and specificities of 95-100% as compared to a sensitivity of 95% and specificity of 94%, for the existing ruminant-specific assay. Of the five human-specific PCR assays, the assay targeting the Bifidobacterium catenulatum group was the most promising, exhibiting a sensitivity of 100% (with human sewage samples) and a specificity of 87%. When tested on rural water samples that were naturally contaminated by ruminant feces, the three novel PCR assays tested positive with a much greater percentage (52-87%) of samples than the existing ruminant-specific assay (17%). These novel ruminant-specific assays show promise for microbial source tracking and merit further field testing and specificity evaluation.     

噬菌体作为水中病毒指示物的研究进展

噬菌体作为潜在的水中病毒指示生物，可用于污水再生利用过程中的病毒学安全评价、阐明病毒灭活机理以及改进病毒检测方法等领域的研究。介绍了常用的指示噬菌体——SC噬菌体、F—RNA噬菌体和Bacteroides fragilis噬菌体在环境中的分布、存活和去除特性及其作为水质评价和病毒指示生物的研究进展。