Recovery of Cryptosporidium oocysts and Giardia cysts from source water concentrates using immunomagnetic separation

Evaluation of molecular-based methods for the detection and quantification of Cryptosporidium spp. in wastewater

Cryptosporidium poses significant public health risks as a cause of waterborne disease worldwide. Clinical surveillance of cryptosporidiosis is largely underreported due to the asymptomatic and mildly symptomatic infections, clinical misdiagnoses, and barriers to access testing. Wastewater surveillance overcomes these limitations and could serve as an effective tool for identifying cryptosporidiosis at the population level. Despite its potential, the lack of standardized wastewater surveillance methods for Cryptosporidium spp. challenges implementation design and the comparability between studies. Thus, this study compared and contrasted Cryptosporidium wastewater surveillance methods for concentrating wastewater oocysts, extracting oocyst DNA, and detecting Cryptosporidium genetic markers. The evaluated concentration methods included electronegative membrane filtration, Envirocheck HV capsule filtration, centrifugation, and Nanotrap Microbiome Particles, with and without additional immunomagnetic separation purification (except for the Nanotrap Microbiome Particles). Oocyst DNA extraction by either the DNeasy Powersoil Pro kit and the QIAamp DNA Mini kit were evaluated and the impact of bead beating and freeze-thaw pretreatments on DNA recoveries was assessed. Genetic detection via qPCR assays targeting either the Cryptosporidium 18S rRNA gene or the Cryptosporidium oocyst wall protein gene were tested. Oocyst recovery percentages were highest for centrifugation (39-77 %), followed by the Nanotrap Microbiome Particles (24 %), electronegative filtration with a PBST elution (22 %), and Envirocheck HV capsule filtration (13 %). Immunomagnetic separation purification was found to be unsuitable due to interference from the wastewater matrix. Bead-beating pretreatment enhanced DNA recoveries from both the DNeasy Powersoil Pro kit (314 gc/μL DNA) and the QIAamp DNA Mini kit (238 gc/μL DNA). In contrast, freeze-thaw pretreatment reduced DNA recoveries to under 92 gc/μL DNA, likely through DNA degradation. Finally, while both qPCR assays were specific to Cryptosporidium spp., the 18S rRNA assay had a 5-fold lower detection limit and could detect a wider range of Cryptosporidium spp. than the Cryptosporidium oocyst wall protein assay.

Does each bead count? A reduced-cost approach for recovering waterborne protozoa from challenge water using immunomagnetic separation

Giardia duodenalis and Cryptosporidium spp. are two of the most prominent aetiological agents of waterborne diseases. Therefore, efficient and affordable methodologies for identifying and quantifying these parasites in water are increasingly necessary. USEPA Method 1623.1 is a widely used and validated protocol for detecting these parasites in water samples. It consists of a concentration step, followed by parasite purification and visualization by immunofluorescence microscopy. Although efficient, this method has a high cost particularly due to the immunomagnetic separation (IMS) step, which is most needed with complex and highly contaminated samples. Based on this, the present study aimed to determine whether it is possible to maintain the efficiency of Method 1623.1 while reducing the amount of beads per reaction, using as a matrix the challenge water recommended by the World Health Organization. As for Giardia cysts, a satisfactory recovery efficiency (RE) was obtained using 50% less IMS beads. This was evaluated both with a commercial cyst suspension (56.1% recovery) and an analytical quality assessment (47.5% recovery). Although RE rates obtained for Cryptosporidium parvum did not meet Method 1623.1 criteria in any of the experimental conditions tested, results presented in this paper indicated the relevance of the described adaptations, even in challenge water.

Cryptosporidium parvum decay during air drying and stockpiling of mesophilic anaerobically digested sewage sludge in a simulation experiment and oocyst counts in sludge collected from operational treatment lagoons in Victoria, Australia

The inactivation of Cryptosporidium species oocysts during sewage sludge treatment is important to protect human health when the residual biosolids are applied to agricultural land. Quantifying the decay of Cryptosporidium species during sludge treatment for microbiological assurance purposes is difficult if low numbers are present in wastewater. The rate of decay of Cryptosporidium parvum oocysts during solar/air drying treatment and in sludge stockpiles in temperate environment conditions was simulated in laboratory inoculation experiments using sludge sampled from a mesophilic anaerobic digester. Oocyst numbers were also determined in settled lagoon sludge samples collected from three operational rural wastewater treatment plants (WWTPs). C. parvum oocysts were enumerated by immunomagnetic separation followed by staining with vital dyes and examination by confocal laser scanning microscopy. An air-drying/storage period equivalent to 11 weeks was required for a 1 log₁₀ reduction of viable oocysts inoculated into digested sludge. Oocyst viability in air-dried and stored digested sludge decreased with time, but was independent of sludge desiccation and dry solids (DS) content. No oocysts were detected in sludge samples collected from the anaerobic digester, and the average concentration of oocysts found in settled lagoon sludge from the rural WWTP was 4.6 × 10² oocysts/g DS.

Towards enhanced automated elution systems for waterborne protozoa using megasonic energy

Continuous and reliable monitoring of water sources for human consumption is imperative for public health. For protozoa, which cannot be multiplied efficiently in laboratory settings, concentration and recovery steps are key to a successful detection procedure. Recently, the use of megasonic energy was demonstrated to recover Cryptosporidium from commonly used water industry filtration procedures, forming thereby a basis for a simplified and cost effective method of elution of pathogens. In this article, we report the benefits of incorporating megasonic sonication into the current methodologies of Giardia duodenalis elution from an internationally approved filtration and elution system used within the water industry, the Filta-Max®. Megasonic energy assisted elution has many benefits over current methods since a smaller final volume of eluent allows removal of time-consuming centrifugation steps and reduces manual involvement resulting in a potentially more consistent and more cost-effective method. We also show that megasonic sonication of G. duodenalis cysts provides the option of a less damaging elution method compared to the standard Filta-Max® operation, although the elution from filter matrices is not currently fully optimised. A notable decrease in recovery of damaged cysts was observed in megasonic processed samples, potentially increasing the abilities of further genetic identification options upon isolation of the parasite from a filter sample. This work paves the way for the development of a fully automated and more cost-effective elution method of Giardia from water samples.

Tools and methods for detecting and characterizing giardia, cryptosporidium, and toxoplasma parasites in marine mollusks

Foodborne infections are of public health importance and deeply impact the global economy. Consumption of bivalve mollusks generates risk for humans because these filtering aquatic invertebrates often concentrate microbial pathogens from their environment. Among them, Giardia, Cryptosporidium, and Toxoplasma are major parasites of humans and animals that may retain their infectivity in raw or undercooked mollusks. This review aims to detail current and future tools and methods for ascertaining the load and potential infectivity of these parasites in marine bivalve mollusks, including sampling strategies, parasite extraction procedures, and their characterization by using microscopy and/or molecular techniques. Method standardization should lead to better risk assessment of mollusks as a source of these major environmental parasitic pathogens and to the development of safety regulations, similar to those existing for bacterial and viral pathogens encountered in the same mollusk species.

The concentration of Cryptosporidium and Giardia in water--the role and importance of recovery efficiency

The concentration of Cryptosporidium and of Giardia in surface water is a subject of importance to public health and public water supply. The term concentration is a fundamental property of any water quality parameter having a classical definition as used in chemistry and biology. Analytical methods for measuring the occurrence of Cryptosporidium and Giardia in water find only a fraction of the organisms actually present. This paper collects recently available data to examine the role and importance of recovery efficiency measurement to description of the concentrations of these organisms. Data from Australian sources graphically illustrate the variability of recovery efficiency at individual sites over relatively short time scales. Additional data on replicated recovery measurements establish their reproducibility. The recently released USEPA LT2 data along with those from Australia illustrate the independent variation of Cryptosporidium and Giardia occurrence and recovery efficiency at individual sampling locations. Calculation of concentration from paired raw numbers and recovery efficiency measurements clearly shows the magnitude and importance of taking recovery into account in expressing the concentration of these organisms.

Immunomagnetic separation significantly improves the sensitivity of polymerase chain reaction in detecting Giardia duodenalis and Cryptosporidium spp. in dairy cattle

The effectiveness of molecular methods for the detection of species of Giardia and Cryptosporidium in fecal samples is often reduced by low or intermittent cyst and oocyst shedding, and/or the presence of polymerase chain reaction (PCR) inhibitors. The present study investigates the use of immunomagnetic separation (IMS) as an additional concentration step before PCR in the detection of these common protozoan parasites in dairy cattle. The IMS-PCR assays were optimized for amplifying fragments of the 16S ribosomal RNA (rRNA), β-giardin, and glutamate dehydrogenase (GDH) genes of Giardia duodenalis, as well as fragments of the 18S rRNA, heat shock protein (HSP)-70, and Cryptosporidium oocyst wall protein (COWP) genes of Cryptosporidium spp. In all cases, IMS-PCR was more sensitive than PCR alone. A significantly greater number of Giardia-positive samples were identified using IMS-PCR of the 16S rRNA gene (P < 0.01) and of the GDH gene (P < 0.01), as compared with PCR without any additional concentration step. In the case of Cryptosporidium, IMS-PCR of the COWP gene (P  =  0.02) resulted in a significantly greater number of positives than did PCR without the IMS concentration step. The greatest number of positives, however, was obtained using IMS-PCR to amplify a portion of the 16S rRNA gene of Giardia and a portion of the HSP-70 gene of Cryptosporidium. A further comparison of the optimized IMS-PCR assays to immunofluorescence microscopy suggested that the IMS-PCR assays were considerably more sensitive than microscopy was in the detection of Giardia cysts and Cryptosporidium oocysts in fecal samples.

Solar drinking water disinfection (SODIS) to reduce childhood diarrhoea in rural Bolivia: a cluster-randomized, controlled trial

BACKGROUND

Solar drinking water disinfection (SODIS) is a low-cost, point-of-use water purification method that has been disseminated globally. Laboratory studies suggest that SODIS is highly efficacious in inactivating waterborne pathogens. Previous field studies provided limited evidence for its effectiveness in reducing diarrhoea.

METHODS AND FINDINGS

We conducted a cluster-randomized controlled trial in 22 rural communities in Bolivia to evaluate the effect of SODIS in reducing diarrhoea among children under the age of 5 y. A local nongovernmental organisation conducted a standardised interactive SODIS-promotion campaign in 11 communities targeting households, communities, and primary schools. Mothers completed a daily child health diary for 1 y. Within the intervention arm 225 households (376 children) were trained to expose water-filled polyethyleneteraphtalate bottles to sunlight. Eleven communities (200 households, 349 children) served as a control. We recorded 166,971 person-days of observation during the trial representing 79.9% and 78.9% of the total possible person-days of child observation in intervention and control arms, respectively. Mean compliance with SODIS was 32.1%. The reported incidence rate of gastrointestinal illness in children in the intervention arm was 3.6 compared to 4.3 episodes/year at risk in the control arm. The relative rate of diarrhoea adjusted for intracluster correlation was 0.81 (95% confidence interval 0.59-1.12). The median length of diarrhoea was 3 d in both groups.

CONCLUSIONS

Despite an extensive SODIS promotion campaign we found only moderate compliance with the intervention and no strong evidence for a substantive reduction in diarrhoea among children. These results suggest that there is a need for better evidence of how the well-established laboratory efficacy of this home-based water treatment method translates into field effectiveness under various cultural settings and intervention intensities. Further global promotion of SODIS for general use should be undertaken with care until such evidence is available.

TRIAL REGISTRATION

www.ClinicalTrials.govNCT00731497 Please see later in the article for Editors' Summary.

Cryptosporidium--biotechnological advances in the detection, diagnosis and analysis of genetic variation

Cryptosporidiosis is predominantly a gastrointestinal disease of humans and other animals, caused by various species of protozoan parasites representing the genus Cryptosporidium. This disease, transmitted mainly via the faecal-oral route (in water or food), is of major socioeconomic importance worldwide. The diagnosis and genetic characterization of the different species and population variants (usually recognised as "genotypes" or "subgenotypes") of Cryptosporidium is central to the prevention, surveillance and control of cryptosporidiosis, particularly given that there is presently no broadly applicable treatment regimen for this disease. Although traditional phenotypic techniques have had major limitations in the specific diagnosis of cryptosporidiosis, there have been major advances in the development of molecular analytical and diagnostic tools. This article provides a concise account of Cryptosporidium and cryptosporidiosis, and focuses mainly on recent advances in nucleic acid-based approaches for the diagnosis of cryptosporidiosis and analysis of genetic variation within and among species of Cryptosporidium. These advances represent a significant step toward an improved understanding of the epidemiology as well as the prevention and control of cryptosporidiosis.

Detection of Toxoplasma gondii in water by an immunomagnetic separation method targeting the sporocysts

An immunomagnetic separation (IMS) method was developed to detect Toxoplasma gondii in fresh waters by using the monoclonal antibody 4B6 targeting the sporocyst wall of T. gondii, Hammondia hammondi, Hammondia heydorni, and Neospora caninum. Water concentrates obtained by filtering 10- to 20-l samples samples were spiked with Toxoplasma oocysts, sonicated to release the sporocysts, and analyzed by IMS-4B6. Mean sporocyst recoveries were 74.5 +/- 5.3% in drinking water, 30.6 +/- 2.4 and 37.1 +/- 3.2% in surface waters, and 81.6 +/- 2.1% in IMS buffer. Then, this IMS method was integrated in a multistep procedure (i.e., filtration, IMS, immunofluorescence and autofluorescence) to detect Toxoplasma in unspiked and spiked water samples (10-30 l) of various qualities. Sporocyst recoveries ranged from 14.4 to 44.7% in drinking water samples spiked with 1-10 oocysts/l, and from 17.8 to 32.5% in surface water samples spiked with 10 oocysts/l. Sporocysts were not detected in 25 unspiked water samples. A sporocyst-like structure was seen in one of these unspiked samples, but its coccidian nature could not be proved by three polymerase chain reaction (PCR) methods targeting sequences of coccidian small and large subunit rRNA genes and Toxoplasma repetitive elements. In conclusion, IMS-4B6 is relevant for the detection of Toxoplasma in water generating small concentrates (<1 ml). Due to 4B6 cross-reactions, a PCR would be useful to further characterize coccidian sporocysts found microscopically.

Comparison of most probable number-PCR and most probable number-foci detection method for quantifying infectious Cryptosporidium parvum oocysts in environmental samples

Microbial contamination of public water supplies is of significant concern, as numerous outbreaks, including Cryptosporidium, have been reported worldwide. Detection and enumeration of Cryptosporidium parvum oocysts in water supplies is important for the prevention of future cryptosporidiosis outbreaks. In addition to not identifying the oocyst species, the U.S. EPA Method 1622 does not provide information on oocyst viability or infectivity. As such, current detection strategies have been coupled with in vitro culture methods to assess oocyst infectivity. In this study, a most probable number (MPN) method was coupled with PCR (MPN-PCR) to quantify the number of infectious oocysts recovered from seeded raw water concentrates. The frequency of positive MPN-PCR results decreased as the oocyst numbers decreased. Similar results were observed when MPN was coupled to the foci detection method (MPN-FDM), which was done for comparison. For both methods, infectious oocysts were not detected below 10(3) seeded oocysts and the MPN-PCR and MPN-FDM estimates for each seed dose were generally within one-log unit of directly enumerated foci of infection. MPN-PCR estimates were 0.25, 0.54, 0 and 0.66 log(10) units higher than MPN-FDM estimates for the positive control, 10(5), 10(4) and 10(3) seed doses, respectively. The results show the MPN-PCR was the better method for the detection of infectious C. parvum oocysts in environmental water samples.

Detection of infectious parasites in reclaimed water

The presence of infectious protozoan pathogens in reclaimed water may present an unacceptable health risk. This study was designed similar to a study reported by Garcia et al. (2002), which detected no infectious Giardia cysts in the final effluent of a tertiary treatment facility as determined by animal infectivity (dose 1000 cysts/gerbil). This study also included evaluation of Cryptosporidium oocyst infectivity. Infectious Giardia cysts were detected in the final effluent with 1 gerbil out of 3 inoculated with 250 cysts from reclaimed water showing signs of infection 15 days postinoculation. None of the Cryptosporidium oocysts concentrated from the reclaimed water samples appeared to be infectious.

Monitoring of Cryptosporidium and Giardia in the Vantaa river basin, southern Finland

We compared two sampling methods to assess the contamination of the Vantaa river basin by Giardia cysts and Cryptosporidium oocysts: 10-1 grab samples, the common river mussel Anadonta piscinalis, were analysed for concentration of (oo)cysts from river water. The samples were collected 2-5 times in autumn 2001 from four wastewater treatment plants and four river water sites located downstream of the plants, and six times from raw water of a drinking water plant using the river as water source. The presence of Giardia and Cryptosporidium was analysed by IF microscopy and PCR. Both cysts and oocysts were detected at all sampling sites, but oocysts were more common than cysts in river water samples. In contrast, cysts were more common in A. piscinalis. Most Cryptosporidium-positive samples were of genotype 2 and Giardia were assemblage B. In river water, MPN of Escherichia coli did not correlate to the presence of (oo)cysts. In conclusion, low (oo)cyst counts were regularly identified in the Vantaa river basin which is contaminated by discharges of treated wastewater of human origin. In general, both methods to appropriate to detect (oo)cysts, but grab samples yielded more positive results. Grab sampling is also more practical and less expensive than analysis of A. piscinalis.

Immunomagnetic separation of Toxoplasma gondii oocysts using a monoclonal antibody directed against the oocyst wall

Recent outbreaks of waterborne toxoplasmosis have stimulated the development of sensitive methods to detect Toxoplasma gondii oocysts in samples suspected to be contaminated. The immunomagnetic separation (IMS) have been standardised to detect waterborne protozoa, but it did not exist for Toxoplasma oocysts. In this study, we describe two monoclonal antibodies (mAbs 3G4 and 4B6) produced against the oocyst wall, and the incorporation of mAb 3G4 in an IMS procedure. We found that an indirect IMS method gave better mean recoveries than a direct one (69.4% and 25.2%, respectively). Dissociation of oocyst_magnetic bead complexes was greatly improved by using a 2% aqueous H2SO4 solution instead of a 0.1 N HCl solution (82.8% and 17.4%, respectively). With these parameters, mean recoveries of less than 1000 oocysts ranged from 44.6% to 82.9%, depending on incubating temperature and buffer. Age of oocysts (1 or 12 months old) does not influence IMS performances. Results of this study indicate that the described IMS is an efficient technique to recover Toxoplasma oocysts.

Detection and discrimination of Cryptosporidium parvum and C. hominis in water samples by immunomagnetic separation-PCR

Cryptosporidium parvum and C. hominis have been the cause of large and serious outbreaks of waterborne cryptosporidiosis. A specific and sensitive recovery-detection method is required for control of this pathogen in drinking water. In the present study, nested PCR-restriction fragment length polymorphism (RFLP), which targets the divergent Cpgp40/15 gene, was developed. This nested PCR detected only the gene derived from C. parvum and C. hominis strains, and RFLP was able to discriminate between the PCR products from C. parvum and C. hominis. To evaluate the sensitivity of nested PCR, C. parvum oocysts inoculated in water samples of two different turbidities were recovered by immunomagnetic separation (IMS) and detected by nested PCR and fluorescent antibody assay (FA). Genetic detection by nested PCR and oocyst number confirmed by FA were compared, and the results suggested that detection by nested PCR depends on the confirmed oocyst number and that nested PCR in combination with IMS has the ability to detect a single oocyst in a water sample. We applied an agitation procedure with river water solids to which oocysts were added to evaluate the recovery and detection by the procedure in environmental samples and found some decrease in the rate of detection by IMS.

Improvement of recoveries for the determination of protozoa Cryptosporidium and Giardia in water using method 1623

The U.S. Environmental Protection Agency has developed method 1623 for simultaneous detection of Cryptosporidium oocysts and Giardia cysts in water. Method 1623 includes four major steps: filtration, immunomagnetic separation (IMS), fluorescent antibody (FA) staining and microscopic examination. It was noted that the recovery levels following IMS-FA and FA staining were high, averaging more than 92.0% and 89.0% for C. parvum oocysts and G. lamblia cysts, respectively. In contrast, when the filtration step was incorporated, the recovery level of C. parvum oocysts declined significantly to 18.1% in seeded tap water, while a relatively high recovery level of 77.2% for G. lamblia cysts could still be achieved. Further study indicated that the recovery level of C. parvum oocysts could be enhanced significantly when an appropriate amount of silica particles was added to a water sample. The recovery level of C. parvum oocysts was affected by particle size and concentration. The optimal silica particle size was determined to be within the range of 5-40 microm, and the corresponding optimal silica concentration was 1.42 g for 10-l tap water. When both G. lamblia cysts and C. parvum oocysts were spiked into the tap water sample containing the optimum amount of silica particles, the average recovery levels of oocysts and cysts were 82.7% and 75.4%, respectively. The results obtained clearly suggested that addition of an appropriate amount of silica particles could improve the recovery level of C. parvum oocysts significantly and yet there was no noticeable deleterious effect on the recovery level of G. lamblia cysts. Further study indicated that the rotation time in the IMS procedure using the Dynal GC-Combo IMS kit (which was recommended in method 1623) was important for G. lamblia cyst detection. In contrast, the recovery level of C. parvum oocysts was not affected by the rotation time. Furthermore, it was found that the recovery levels of C. parvum oocysts using methods 1622 and 1623 were quite close although different IMS kits were used in the two methods.

Biology, persistence and detection of Cryptosporidium parvum and Cryptosporidium hominis oocyst

Cryptosporidium parvum and Cryptosporidium hominis are obligate enteric protozoan parasites which infect the gastrointestinal tract of animals and humans. The mechanism(s) by which these parasites cause gastrointestinal distress in their hosts is not well understood. The risk of waterborne transmission of Cryptosporidium is a serious global issue in drinking water safety. Oocysts from these organisms are extremely robust, prevalent in source water supplies and capable of surviving in the environment for extended periods of time. Resistance to conventional water treatment by chlorination, lack of correlation with biological indicator microorganisms and the absence of adequate methods to detect the presence of infectious oocysts necessitates the development of consistent and effective means of parasite removal from the water supply. Additional research into improving water treatment and sewage treatment practices is needed, particularly in testing the efficiency of ozone in oocyst inactivation. Timely and efficient detection of infectious C. parvum and C. hominis oocysts in environmental samples requires the development of rapid and sensitive techniques for the concentration, purification and detection of these parasites. A major factor confounding proper detection remains the inability to adequately and efficiently concentrate oocysts from environmental samples, while limiting the presence of extraneous materials. Molecular-based techniques are the most promising methods for the sensitive and accurate detection of C. parvum and C. hominis. With the availability of numerous target sequences, RT-PCR will likely emerge as an important method to assess oocyst viability. In addition, a multiplex PCR for the simultaneous detection of C. parvum, C. hominis and other waterborne pathogens such as Giardia lamblia would greatly benefit the water industry and protect human health.

How to detect Toxoplasma gondii oocysts in environmental samples?

Detection of Toxoplasma gondii oocysts in environmental samples is a great challenge for researchers as this coccidian parasite can be responsible for severe infections in humans and in animals via ingestion of a single oocyst from contaminated water, soil, fruits or vegetables. Despite field investigations, oocysts have been rarely recovered from the environment due to the lack of sensitive methods. Immunomagnetic separation, fluorescence-activated cell sorting, and polymerase chain reaction have recently shown promising use in detection of protozoa from complex matrices. Such procedures could be applied to T. gondii detection, if studies on the antigenic and biochemical composition of the oocyst wall are completed. Using such methods, it will be possible to assess the occurrence, prevalence, viability and virulence of T. gondii oocysts in environmental matrices and specify sources of human and animal contamination.

Assessment of methods for detection of infectious Cryptosporidium oocysts and Giardia cysts in reclaimed effluents

This study evaluates the occurrence of Cryptosporidium oocysts and Giardia cysts in reclaimed effluents if method 1623 with the Envirochek capsule filters (standard and high-volume [HV] filters) and a modified version of the Information Collection Rule method (ICR) with the polypropylene yarn-wound cartridge filter are used. The recovery efficiency of the analytical methods was evaluated with samples of reagent, tap, and reclaimed water by using flow cytometer-sorted spike suspensions. (Oo)cyst recovery efficiency determined filter performance and method reproducibility in the water matrix tested. Method 1623 with the Envirochek HV capsule filter generated significantly higher recovery rates than did the standard Envirochek filter and the modified ICR method. Notwithstanding, large variations in recovery rates (>80%) occurred with samples of reclaimed water, and none of the water quality parameters analyzed in the reclaimed effluents could explain such variability. The highest concentrations of indigenous oocysts were detected by method 1623 with the HV filter, which provided a sufficient number of oocysts for further confirmation of infectious potential. Confirmation of species and potential infectivity for all positive protozoan samples was made by using a nested PCR restriction fragment polymorphism assay and the focus detection method most-probable-number assay, respectively. The methodology and results described in the present investigation provide useful information for the establishment of pathogen numeric standards for reclaimed effluents used for unrestricted irrigation.

Comparison of immunofluorescence assay and immunomagnetic electrochemiluminescence in detection of Cryptosporidium parvum oocysts in karst water samples

Immunofluorescence assay (IFA) and immunomagnetic electrochemiluminescence (IM-ECL) were used for comparison of the percent recovery of Cryptosporidium parvum in environmental water samples obtained from a spring draining a karst basin. The monoclonal antibodies to C. parvum, isotype IgG3 were used for optimization of the IM-ECL protocol. The combination of biotinylated and TAG-labeled anti-C. parvum antibodies with the streptavidin beads gave a linear regression slope for log ECL vs. log fresh oocysts of 0.79 (from 5 to 5,000 oocysts), which indicates a constant ECL signal per oocyst. Standard curves gave a dynamic range of 5 to 5,000 oocysts/ml (fresh) and 10 to 100,000 cells/ml (4-month-old oocysts) with the maximum limit of linear detection higher than 100,000. The linear slope of 4-month-old oocysts decreased to 0.62, which indicates that ECL signal is a function of oocyst age. The experiment associated with bead storage time shows that even after 4 months of storage of the biotinylated antibodies, the complex retains the ability for binding the oocysts and generating the ECL signal. Based on the IFA results in the experiment evaluating different protocols for oocysts recovery from karst water samples, the most efficient protocol involved dispersion, followed by flotation and immunomagnetic separation (IMS) (24% recovery). The ECL results obtained in that experiment were very similar to the results obtained in the IFA method, which indicates that the IM-ECL method is accurate. Results of the IFA in the study of the prevalence of C. parvum in the groundwater showed that oocysts were present in 78% of 1 L water samples with average number of oocysts of 6.4+/-5.5 and ranged from 0 (13 samples) to 23.3 (2 samples). The ECL signal generated from these water samples ranged from 3,771 to 622 (average 1,620+/-465). However, the background value estimated in groundwater samples with low number of oocysts detected by IFA was highly variable and elevated (from 3,702 to 272, average 1,503+/-475). The background value as a result of nonspecific binding to beads by unidentified organic components in the water can inhibit or even completely mask the signal generated by oocysts. Our investigations showed that the IM-ECL method appears to be promising for the qualitative and quantitative detection of C. parvum from the environmental water; however, the method requires further development to improve sensitivity and account for background signals.

Modifications to United States Environmental Protection Agency methods 1622 and 1623 for detection of Cryptosporidium oocysts and Giardia cysts in water

Collaborative and in-house laboratory trials were conducted to evaluate Cryptosporidium oocyst and Giardia cyst recoveries from source and finished-water samples by utilizing the Filta-Max system and U.S. Environmental Protection Agency (EPA) methods 1622 and 1623. Collaborative trials with the Filta-Max system were conducted in accordance with manufacturer protocols for sample collection and processing. The mean oocyst recovery from seeded, filtered tap water was 48.4% +/- 11.8%, while the mean cyst recovery was 57.1% +/- 10.9%. Recovery percentages from raw source water samples ranged from 19.5 to 54.5% for oocysts and from 46.7 to 70.0% for cysts. When modifications were made in the elution and concentration steps to streamline the Filta-Max procedure, the mean percentages of recovery from filtered tap water were 40.2% +/- 16.3% for oocysts and 49.4% +/- 12.3% for cysts by the modified procedures, while matrix spike oocyst recovery percentages ranged from 2.1 to 36.5% and cyst recovery percentages ranged from 22.7 to 68.3%. Blinded matrix spike samples were analyzed quarterly as part of voluntary participation in the U.S. EPA protozoan performance evaluation program. A total of 15 blind samples were analyzed by using the Filta-Max system. The mean oocyst recovery percentages was 50.2% +/- 13.8%, while the mean cyst recovery percentages was 41.2% +/- 9.9%. As part of the quality assurance objectives of methods 1622 and 1623, reagent water samples were seeded with a predetermined number of Cryptosporidium oocysts and Giardia cysts. Mean recovery percentages of 45.4% +/- 11.1% and 61.3% +/- 3.8% were obtained for Cryptosporidium oocysts and Giardia cysts, respectively. These studies demonstrated that the Filta-Max system meets the acceptance criteria described in U.S. EPA methods 1622 and 1623.

Immunomagnetic separation (IMS)-fluorescent antibody detection and IMS-PCR detection of seeded Cryptosporidium parvum oocysts in natural waters and their limitations

Detection and enumeration of Cryptosporidium parvum in both treated and untreated waters are important to facilitate prevention of future cryptosporidiosis incidents. Immunomagnetic separation (IMS)-fluorescent antibody (FA) detection and IMS-PCR detection efficiencies were evaluated in two natural waters seeded with nominal seed doses of 5, 10, and 15 oocysts. IMS-FA detected oocysts at concentrations at or below the three nominal oocyst seed doses, illustrating that IMS-FA is sensitive enough to detect low oocyst numbers. However, the species of the oocysts could not be determined with this technique. IMS-PCR, targeting the 18S rRNA gene in this study, yielded positive amplification for 17 of the 18 seeded water samples, and the amplicons were subjected to restriction fragment length polymorphism digestion and DNA sequencing for species identification. Interestingly, the two unseeded, natural water samples were also PCR positive; one amplicon was the same base pair size as the C. parvum amplicon, and the other amplicon was larger. These two amplified products were determined to be derived from DNA of Cryptosporidium muris and a dinoflagellate. These IMS-PCR results illustrate that (i) IMS-PCR is able to detect low oocyst numbers in natural waters, (ii) PCR amplification alone is not confirmatory for detection of target DNA when environmental samples are used, (ii) PCR primers, especially those designed against the rRNA gene region, need to be evaluated for specificity with organisms closely related to the target organism, and (iv) environmental amplicons should be subjected to appropriate species-specific confirmatory techniques.

Cryptosporidium parvum and Cyclospora cayetanensis: a review of laboratory methods for detection of these waterborne parasites

Cryptosporidium and Cyclospora are obligate, intracellular, coccidian protozoan parasites that infest the gastrointestinal tract of humans and animals causing severe diarrhea illness. In this paper, we present an overview of the conventional and more novel techniques that are currently available to detect Cryptosporidium and Cyclospora in water. Conventional techniques and new immunological and genetic/molecular methods make it possible to assess the occurrence, prevalence, virulence (to a lesser extent), viability, levels, and sources of waterborne protozoa. Concentration, purification, and detection are the three key steps in all methods that have been approved for routine monitoring of waterborne oocysts. These steps have been optimized to such an extent that low levels of naturally occurring Cryptosporidium oocysts can be efficiently recovered from water. The filtration systems developed in the US and Europe trap oocysts more effectively and are part of the standard methodologies for environmental monitoring of Cryptosporidium oocysts in source and treated water. Purification techniques such as immunomagnetic separation and flow cytometry with fluorescent activated cell sorting impart high capture efficiency and selective separation of oocysts from sample debris. Monoclonal antibodies with higher avidity and specificity to oocysts in water concentrates have significantly improved the detection and enumeration steps. To date, PCR-based detection methods allow us to differentiate the human pathogenic Cryptosporidium parasites from those that do not infect humans, and to track the source of oocyst contamination in the environment. Cell culture techniques are now used to examine oocyst viability. While fewer studies have focused on Cyclospora cayetanensis, the parasite has been successfully detected in drinking water and wastewater using current methods to recover Cryptosporidium oocysts. More research is needed for monitoring of Cyclospora in the environment. Meanwhile, molecular methods (e.g. molecular markers such as intervening transcribed spacer regions), which can identify different genotypes of C. cayetanensis, show good promise for detection of this emerging coccidian parasite in water.