Evaluation of five membrane filtration methods for recovery of Cryptosporidium and Giardia isolates from water samples

Fate of Cryptosporidium and Giardia through conventional and compact drinking water treatment plants

Over the past three decades, a notable rise in the occurrence of enteric protozoan pathogens, especially Giardia and Cryptosporidium spp., in drinking water sources has been observed. This rise could be attributed not only to an actual increase in water contamination but also to improvements in detection methods. These waterborne pathogens have played a pivotal role in disease outbreaks and the overall escalation of disease rates in both developed and developing nations worldwide. Consequently, the control of waterborne diseases has become a vital component of public health policies and a primary objective of drinking water treatment plants (DWTPs). Limited studies applied real-time PCR (qPCR) and/or immunofluorescence assay (IFA) for monitoring Giardia and Cryptosporidium spp., particularly in developing countries like Egypt. Water samples from two conventional drinking water treatment plants and two compact units (CUs) were analyzed using both IFA and qPCR methods to detect Giardia and Cryptosporidium. Using qPCR and IFA, the conventional DWTPs showed complete removal of Giardia and Cryptosporidium, whereas Mansheyat Alqanater and Niklah CUs achieved only partial removal. Specifically, Cryptosporidium gene copies removal rates were 33.33% and 60% for Mansheyat Alqanater and Niklah CUs, respectively. Niklah CU also removed 50% of Giardia gene copies, but no Giardia gene copies were removed by Mansheyat Alqanater CU. Using IFA, both Mansheyat Alqanater and Niklah CUs showed a similar removal rate of 50% for Giardia cysts. Additionally, Niklah CU achieved a 50% removal of Cryptosporidium oocysts, whereas Mansheyat Alqanater CU did not show any removal of Cryptosporidium oocysts. Conventional DWTPs were more effective than CUs in removing enteric protozoa. The contamination of drinking water by enteric pathogenic protozoa remains a significant issue globally, leading to increased disease rates. Infectious disease surveillance in drinking water is an important epidemiological tool to monitor the health of a population.

Impact of filter material and holding time on spore sampling efficiency in water

Bacillus anthracis and other environmentally persistent pathogens pose a significant threat to human and environmental health. If contamination is spread over a wide area (e.g. resulting from a bioterrorism or biowarfare incident), readily deployable and scalable sample collection methods will be necessary for rapidly developing and implementing effective remediation strategies. A recent surge in environmental (eDNA) sampling technologies could prove useful for quantifying the extent and levels of contamination from biological agents in environmental and drinking water. In this study, three commonly used membrane filtration materials (cellulose acetate, cellulose nitrate, and nylon) were evaluated for spore filtration efficiency, yielding recoveries from 17%-68% to 25%-117% for high and low titer samples, respectively, where cellulose nitrate filters generated the highest recoveries. A holding time test revealed no statistically significant differences between spore recoveries when analyzed at the specified timepoints, suggesting that eDNA filter sampling techniques can yield and maintain a relatively high recovery of spores for an extended period of time between filtration and analysis without a detrimental impact on spore recoveries. The results shown here indicate that emerging eDNA technologies could be leveraged for sampling following a wide-area contamination incident and for other microbiological water sampling applications.

Low-cost internal controls for detection of Giardia cysts in water samples

Giardia cysts stained with hot carbolfuchsin were used as internal controls in a concentration method for surface water samples. The morphological integrity of stained cysts and the stain's stability and intensity were tested with each of the chemical reagents used in the aluminum sulfate flocculation method. No alterations in morphology or color were noted. The stained cyst preparation has a low cost, high stability, and suitability for both light and immunofluorescent microscopy, making it affordable to researchers in low- and middle-income countries.

Label-Free Capacitive Biosensor for Detection of Cryptosporidium

Cryptosporidium, an intestinal protozoan pathogen, is one of the leading causes of diarrhea in healthy adults and death in children. Detection of Cryptosporidium oocysts has become a high priority to prevent potential outbreaks. In this paper, a label-free interdigitated-based capacitive biosensor has been introduced for the detection of Cryptosporidium oocysts in water samples. Specific anti-Cryptosporidium monoclonal antibodies (IgG3) were covalently immobilized onto interdigitated gold electrodes as the capture probes, and bovine serum albumin was used to avoid non-specific adsorption. The immobilization of the antibodies was confirmed by measuring the change in the contact angle. The detection was achieved by measuring the relative change in the capacitive/dielectric properties due to the formation of Cryptosporidium-antibody complex. The biosensor has been tested for different concentrations of Cryptosporidium. The results show that the biosensor developed can accurately distinguish different numbers of captured cells and densities on the surface of the biosensor. The number of Cryptosporidium oocysts captured on the electrode surface was confirmed using a fluorescein isothiocyanate (FITC) immunofluorescence assay. The response from the developed biosensor has been mainly dependent on the concentration of Cryptosporidium under optimized conditions. The biosensor showed a linear detection range between 15 and 153 cells/mm² and a detection limit of 40 cells/mm². The label-free capacitive biosensor developed has a great potential for detecting Cryptosporidium in environmental water samples. Furthermore, under optimized conditions, this label-free biosensor can be extended for detection of other biomarkers for biomedical and environmental analyses.

Chemical and microbial characteristics of municipal drinking water supply systems in the Canadian Arctic

Drinking water in the vast Arctic Canadian territory of Nunavut is sourced from surface water lakes or rivers and transferred to man-made or natural reservoirs. The raw water is at a minimum treated by chlorination and distributed to customers either by trucks delivering to a water storage tank inside buildings or through a piped distribution system. The objective of this study was to characterize the chemical and microbial drinking water quality from source to tap in three hamlets (Coral Harbour, Pond Inlet and Pangnirtung-each has a population of <2000) on trucked service, and in Iqaluit (population ~6700), which uses a combination of trucked and piped water conveyance. Generally, the source and drinking water was of satisfactory microbial quality, containing Escherichia coli levels of <1 MPN/100 mL with a few exceptions, and selected pathogenic bacteria and parasites were below detection limits using quantitative polymerase chain reaction (qPCR) methods. Tap water in households receiving trucked water contained less than the recommended 0.2 mg/L of free chlorine, while piped drinking water in Iqaluit complied with Health Canada guidelines for residual chlorine (i.e. >0.2 mg/L free chlorine). Some buildings in the four communities contained manganese (Mn), copper (Cu), iron (Fe) and/or lead (Pb) concentrations above Health Canada guideline values for the aesthetic (Mn, Cu and Fe) and health (Pb) objectives. Corrosion of components of the drinking water distribution system (household storage tanks, premise plumbing) could be contributing to Pb, Cu and Fe levels, as the source water in three of the four communities had low alkalinity. The results point to the need for robust disinfection, which may include secondary disinfection or point-of-use disinfection, to prevent microbial risks in drinking water tanks in buildings and ultimately at the tap.

Giardia duodenalis in the UK: current knowledge of risk factors and public health implications

Giardia duodenalis is a ubiquitous flagellated protozoan parasite known to cause giardiasis throughout the world. Potential transmission vehicles for this zoonotic parasite are both water and food sources. As such consumption of water contaminated by feces, or food sources washed in contaminated water containing parasite cysts, may result in outbreaks. This creates local public health risks which can potentially cause widespread infection and long-term post-infection sequelae. This paper provides an up-to-date overview of G. duodenalis assemblages, sub-assemblages, hosts and locations identified. It also summarizes knowledge of potential infection/transmission routes covering water, food, person-to-person infection and zoonotic transmission from livestock and companion animals. Public health implications focused within the UK, based on epidemiological data, are discussed and recommendations for essential Giardia developments are highlighted.

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.

Bioaccumulation of Toxoplasma and Cryptosporidium by the freshwater crustacean Gammarus fossarum: Involvement in biomonitoring surveys and trophic transfer

The protozoa Toxoplasma gondii and Cryptosporidium parvum are public health priorities because their oocysts can persist in recreational, surface, drinking, river, and sea water sources for a long time. To evaluate the capacity of the freshwater crustacean Gammarus fossarum to accumulate T. gondii and C. parvum oocysts, gammarids were exposed to 200, 2000 or 20,000 oocysts per gammarid and per day for 21 days followed by 5 days of depuration. C. parvum DNA was detected by qPCR in G. fossarum in only one out of four pools for the highest concentration and after 14 days of exposure, and T. gondii DNA was detected after 7 days of exposure to the two highest concentrations. Our results document the capacity of G. fossarum to accumulate T. gondii in its tissues proportionally to the ambient concentration; the maximum number of oocysts was detected in gammarid tissues after exposure to 20,000 oocysts per day. Mean values of 3.26 (±3), 21.71 (±15.18), and 17.41 (±10.89) oocysts were detected in gammarids after 7, 14, and 21 days, respectively, and after 5 days of depuration, T. gondii oocysts were still present in gammarid tissues. These results show for the first time that a freshwater crustacean can bioaccumulate T. gondii oocysts, suggesting that G. fossarum is a potential effective bioindicator of protozoan contamination in biomonitoring studies. Moreover, due to its key position in freshwater food webs, G. fossarum could also play a role in the trophic transfer of protozoa.

Deformability Assessment of Waterborne Protozoa Using a Microfluidic-Enabled Force Microscopy Probe

Many modern filtration technologies are incapable of the complete removal of Cryptosporidium oocysts from drinking-water. Consequently, Cryptosporidium-contaminated drinking-water supplies can severely implicate both water utilities and consumers. Existing methods for the detection of Cryptosporidium in drinking-water do not discern between non-pathogenic and pathogenic species, nor between viable and non-viable oocysts. Using FluidFM, a novel force spectroscopy method employing microchannelled cantilevers for single-cell level manipulation, we assessed the size and deformability properties of two species of Cryptosporidium that pose varying levels of risk to human health. A comparison of such characteristics demonstrated the ability of FluidFM to discern between Cryptosporidium muris and Cryptosporidium parvum with 86% efficiency, whilst using a measurement throughput which exceeded 50 discrete oocysts per hour. In addition, we measured the deformability properties for untreated and temperature-inactivated oocysts of the highly infective, human pathogenic C. parvum to assess whether deformability may be a marker of viability. Our results indicate that untreated and temperature-inactivated C. parvum oocysts had overlapping but significantly different deformability distributions.

Development of a Filtration-Based Bioluminescence Assay for Detection of Microorganisms in Tea Beverages

The market for tea drinks as healthy beverages has been steadily expanding, and ready-to-drink beverages in polyethylene terephthalate bottles have been popular. To more rapidly and accurately test tea beverages bottled in polyethylene terephthalate for microbial contamination, a newly developed filtration device and a washing method with a commercial bioluminescence assay were combined to detect low numbers of bacterial spores, fungal conidia, and ascospores. Washing buffers were formulated with nonionic detergents from the Tween series. Commercially available tea beverages were used to evaluate the filtration capacity of the filtration device, the effect of washing buffers, and the performance of the assay. The assay was tested with serially diluted suspensions of colonies of two bacterial strains, spores of three Bacillus strains, conidia of five fungal strains, and ascospores of four fungal strains. The filtration device enabled filtration of a large sample volume (100 to 500 ml), and the washing buffer significantly decreased the background bioluminescence intensity of tea samples when compared with the no-washing method. Low numbers (1 to 10 CFU/100 ml) of the tested strains of bacteria were detected within 8 to 18 h of cultivation, and fungi were detected within 24 to 48 h. Furthermore, a whole bottle (500 ml) of mixed tea was filtered through the filtration device and microbes were detected. This method could be used for quality control of bottled beverages without preincubation.

Effective concentration and detection of cryptosporidium, giardia, and the microsporidia from environmental matrices

Cryptosporidium spp., Giardia spp., and members of Microsporidia are enteropathogenic parasites of humans and animals, producing asymptomatic to severe intestinal infections. To circumvent various impediments associated with current detection methods, we tested a method providing multistage purification and separation in a single, confined step. Standard real-time PCR was used as a detection method. Samples spiked with C. parvum and G. intestinalis were split for comparison to standard Method 1623. Results were equivalent to immunomagnetic procedures for Cryptosporidium, and Giardia. Overall percent recovery for Cryptosporidium with Method 1623 averaged 26.89% (std 21.44%; min = 0%; max = 73%) and was similar but less variable for qPCR method at an estimated average of 27.67 (std 17.65%; min = 5%; max = 63%). For Giardia, Method 1623 had an overall average recovery of 27.11% (std 17.98%; min = 1%; max = 58%), while multistage purification and qPCR had an estimated lower overall recovery at 18.58% (std 13.95%; min = 0%; max = 35%). Microsporidia were also readily detected with an estimated recovery of 46.81% overall (std 17.66%; min = 18%; max = 70%) for E. intestinalis and 38.90% (std 14.36%; min = 13%; max = 62%) for E. bieneusi.

A cascade-like silicon filter for improved recovery of oocysts from environmental waters

Standard filtration methods have been characterized by poor recoveries when processing large-volume samples of environmental water. A method to pre-remove particulates present in turbid waters would be necessary to enhance recovery of protozoan oocysts. Particulate separation can be achieved by the proposed multiplex particle refining (MPR) system. This system employs multiple counter-flow microfiltration units that are arranged into a cascade-like structure. By use of this design, the target oocysts are pre-concentrated from environmental waters. The performance of the MPR system was investigated using 10-L deionized water and surface water spiked with 100 Cryptosporidium parvum oocysts. A recovery rate of around 85% was obtained for spiked river water. The water samples were processed using high flow rate and a simple filtration protocol. Further experiments were conducted using the MPR as a pre-filter for five commercially available filters. The recovery rates were two- to threefold higher employing the pre-filter than using the filters alone. The merit of the refining system to use different numbers of counter-flow units led to superior oocyst recovery rate for the Filta-Max and Envirochek HV filters, which are approved by the US Environmental Protection Agency. This work demonstrates a feasible tool for improved filtration performance in environmental waters.

Occurrence and potential health risk of Cryptosporidium and Giardia in the Three Gorges Reservoir, China

The Three Gorges Reservoir (TGR) is the biggest lake in the world and a major water source in China. There is no information about occurrence and impact of Cryptosporidium and Giardia on the aquatic ecosystem. 61 surface water samples from 23 monitoring sites and 5 treated effluent samples were collected and analyzed. Cryptosporidium oocysts and Giardia cysts were found, respectively, in 86.4% and 65.2% of a total of 66 water samples, with high concentrations in treated effluent. The mean percent recovery was 29.14% for oocysts and 34.86% for cysts. A seasonal pattern was observed, with positive samples for Cryptosporidium more frequent in flood period and positive samples for Giardia more frequent in impounding period. Counts of enterococci, fecal coliforms and total coliforms, and turbidity were significantly associated with Cryptosporidium concentration in backwater (water in a main river which is backed up by the Three Gorges Dam) areas of tributaries but not Giardia. High associations were also found between oocyst and cyst in backwater areas of tributaries and cities. The risks of infection and illness due to water consumption in four different exposure routes were estimated. The results showed that swimming in the TGR has the highest infection risk with 1.39 × 10(-3) per time (95% confidence interval (CI): 0.05-600.3 × 10(-5)) for Cryptosporidium and 2.08 × 10(-4) per time (95% CI: 0.05-878.87 × 10(-6)) for Giardia, while directly drinking unboiled tap water treated with the conventional process has the highest morbidity with 524.98 per 100,000 population per year (95% CI: 10.35-2040.26) for Cryptosporidium and 5.89 per 100,000 population per year (95% CI: 0.08-22.67) for Giardia. This study provides new useful information for drinking water plants, health care workers and managers to improve the safety of tap water and deduce the risk of surface water contamination in China.

Determination of the recovery efficiency of cryptosporidium oocysts and giardia cysts from seeded bivalve mollusks

The intestinal parasites Cryptosporidium and Giardia are transmitted by water and food and cause human gastroenteritis. Filter-feeding bivalve mollusks, such as oysters and mussels, filter large volumes of water and thus concentrate such pathogens, which makes these bivalves potential vectors of disease. To assess the risk of infection from consumption of contaminated bivalves, parasite numbers and parasite recovery data are required. A modified immunomagnetic separation (IMS) procedure was used to determine Cryptosporidium oocyst and Giardia cyst numbers in individually homogenized oysters (Crassostrea gigas) and mussels (Mytilus edulis). About 12% of the commercial bivalves were positive, with low (oo)cyst numbers per specimen. The recovery efficiency of the IMS procedure was systematically evaluated. Experiments included seeding of homogenized bivalves and whole animals with 100 to 1,000 (oo)cysts. Both seeding procedures yielded highly variable recovery rates. Median Cryptosporidium recoveries were 7.9 to 21% in oysters and 62% in mussels. Median Giardia recoveries were 10 to 25% in oysters and 110% in mussels. Giardia recovery was significantly higher than Cryptosporidium recovery. (Oo)cysts were less efficiently recovered from seeded whole animals than from seeded homogenates, with median Cryptosporidium recoveries of 5.3% in oysters and 45% in mussels and median Giardia recoveries of 4.0% in oysters and 82% in mussels. Both bivalve homogenate seeding and whole animal seeding yielded higher (oo)cyst recovery in mussels than in oysters, likely because of the presence of less shellfish tissue in IMS when analyzing the smaller mussels compared with the larger oysters, resulting in more efficient (oo)cyst extraction. The data generated in this study may be used in the quantitative assessment of the risk of infection with Cryptosporidium or Giardia associated with the consumption of raw bivalve mollusks. This information may be used for making risk management decisions.

WITHDRAWN: Multiplex particle refining system to enhance Cryptosporidium recovery for surface water filtration methods

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.org/doi:10.1016/j.mimet.2012.12.009. The duplicate article has therefore been withdrawn.

Prevalence and distribution of Cryptosporidium and Giardia in wastewater and the surface, drinking and ground waters in the Lower Rhine, Germany

Samples from different water sources (n = 396) were collected during 2009 and 2011. Wastewater (2-5 l) was purified by aluminium sulphate flocculation. Surface, ground and drinking waters (400-6400 l) were collected by filtration. Cryptosporidium oocysts and Giardia cysts were further concentrated by sucrose centrifugation. (Oo)cysts were identified by IFT (immunofluorescence test), DAPI (4',6-diamidino-2-phenylindole) staining and DICM (difference interference contrast microscopy). Out of 206 wastewater samples, 134 (65·0%) were found to be positive for Giardia cysts and 64 (31·1%) for Cryptosporidium oocysts. Parasite numbers ranged from 0 to 2436 cysts/l and 0 to 1745 oocysts/l. Eight (4·2%) surface and drinking water samples (n = 190) were found to be positive for Giardia cysts (0-56000/100 l), and 18 (9·5%) for Cryptosporidium oocysts (2400/100 l). The purpose of this study was to establish the prevalence and concentrations of Giardia lamblia and Cryptosporidium spp. by detecting (oo)cysts from water samples. This study provides substantial evidence that G. lamblia cysts and Cryptosporidium spp. oocysts are able to enter and circulate in the aquatic environment with negative implications for public health.

Recovery of DNA of Giardia intestinalis cysts from surface water concentrates measured with PCR and real time PCR

The most important restriction for the detection in water samples is the low concentration of Giardia intestinalis cysts, additional difficulty is the presence of PCR inhibitors. We have carried out trials in order to assess the sensitivity of semi-nested PCR and TaqMan real time PCR on the basis of DNA extracted from G. intestinalis cysts coming from spiked environmental and distilled water samples, filtrated with the use of Filta-Max® equipment (1623 Method). Removal of inhibitors was carried out with addition of BSA in different concentrations. During the filtration and concentration of water samples, losses of cysts have been recorded. Moreover, addition of BSA to the PCR and real time PCR mix increases the sensitivity of reaction. The optimal concentration of BSA for semi‑nested PCR was 15 and 20 ng/μl, whereas for real time PCR 5 ng/μl.

Fabrication of multi-layer polymeric micro-sieve having narrow slot pores with conventional ultraviolet-lithography and micro-fabrication techniques

Fast detection of waterborne pathogens is important for securing the hygiene of drinking water. Detection of pathogens in water at low concentrations and minute quantities demands rapid and efficient enrichment methods in order to improve the signal-to-noise ratio of bio-sensors. We propose and demonstrate a low cost and rapid method to fabricate a multi-layer polymeric micro-sieve using conventional lithography techniques. The micro-fabricated micro-sieves are made of several layers of SU-8 photoresist using multiple coating and exposure steps and a single developing process. The obtained micro-sieves have good mechanical properties, smooth surfaces, high porosity (≈40%), and narrow pore size distribution (coefficient of variation < 3.33%). Sample loading and back-flushing using the multi-layer micro-sieve resulted in more than 90% recovery of pathogens, which showed improved performance than current commercial filters.

Cross-flow microfiltration system for rapid enrichment of bacteria in water

Permanent monitoring of waterborne pathogens is important for securing the hygiene of water. Enumerating bacteria in water at low concentrations and minute quantities demands rapid and efficient enrichment methods in order to improve the signal-to-noise ratio of subsequent determination methods. In this work an automated cross-flow microfiltration (CFM) system is presented which is usable in the field to concentrate large volumes of environmental water for analytical purposes. It was designed as a rapid enrichment apparatus achieving high recovery and high concentration factors. The efficiency of the CFM system was studied for E. coli spiked in a 10-L tap water sample. By this technique, a 10-L water sample was concentrated by a factor of 200 in 15 min. The high and consistent recovery of 91.3 +/- 5.4% living cells in the concentration range 0.01 and 100 cfu mL(-1) is suitable for rapid enumeration of bacteria in water.

Portable continuous flow centrifugation and method 1623 for monitoring of waterborne protozoa from large volumes of various water matrices

AIMS

The aims of this study were to validate a portable continuous flow centrifuge (PCFC) as an alternative concentration step of US-EPA Method 1623 and to demonstrate it's efficacy for recovery of low numbers of protozoa from large volumes of various water matrices.

METHODS AND RESULTS

Recoveries of Cryptosporidium parvum oocysts, Giardia intestinalis cysts and Encephalitozoon intestinalis spores spiked into 10-1000 l volumes of various water matrices were evaluated during in-house and collaborative trials. Spiked protozoa were either approved standards or diluted stock samples enumerated according to USEPA Method 1623. Cryptosporidium recoveries exceeded method 1623 criteria and substantially high recoveries were observed for Giardia and E. intestinalis.

CONCLUSIONS

Portable continuous flow centrifuge methodology exceeded method 1623 acceptance criteria for Cryptosporidium and could be easily adopted for other protozoa.

SIGNIFICANCE AND IMPACT OF THE STUDY

The PCFC could be adopted as an alternative user-friendly concentration method for Cryptosporidium and for monitoring of large volumes of source and tap water for accidental or deliberate contamination with protozoa and potentially with other enteric pathogens. It is anticipated that PCFC would also be equal or superior to filtration for protozoa monitoring in wastewater and effluents.