Immunomagnetic capture PCR to detect viable Cryptosporidium parvum oocysts from environmental samples

Past, Present, and Future of Affinity-based Cell Separation Technologies

Progress in cell purification technology is critical to increase the availability of viable cells for therapeutic, diagnostic, and research applications. A variety of techniques are now available for cell separation, ranging from non-affinity methods such as density gradient centrifugation, dielectrophoresis, and filtration, to affinity methods such as chromatography, two-phase partitioning, and magnetic-/fluorescence-assisted cell sorting. For clinical and analytical procedures that require highly purified cells, the choice of cell purification method is crucial, since every method offers a different balance between yield, purity, and bioactivity of the cell product. For most applications, the requisite purity is only achievable through affinity methods, owing to the high target specificity that they grant. In this review, we discuss past and current methods for developing cell-targeting affinity ligands and their application in cell purification, along with the benefits and challenges associated with different purification formats. We further present new technologies, like stimuli-responsive ligands and parallelized microfluidic devices, towards improving the viability and throughput of cell products for tissue engineering and regenerative medicine. Our comparative analysis provides guidance in the multifarious landscape of cell separation techniques and highlights new technologies that are poised to play a key role in the future of cell purification in clinical settings and the biotech industry. STATEMENT OF SIGNIFICANCE: Technologies for cell purification have served science, medicine, and industrial biotechnology and biomanufacturing for decades. This review presents a comprehensive survey of this field by highlighting the scope and relevance of all known methods for cell isolation, old and new alike. The first section covers the main classes of target cells and compares traditional non-affinity and affinity-based purification techniques, focusing on established ligands and chromatographic formats. The second section presents an excursus of affinity-based pseudo-chromatographic and non-chromatographic technologies, especially focusing on magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS). Finally, the third section presents an overview of new technologies and emerging trends, highlighting how the progress in chemical, material, and microfluidic sciences has opened new exciting avenues towards high-throughput and high-purity cell isolation processes. This review is designed to guide scientists and engineers in their choice of suitable cell purification techniques for research or bioprocessing needs.

The European rabbit (Oryctolagus cuniculus), a source of zoonotic cryptosporidiosis

Cryptosporidium spp. have been found in the faeces of over 150 mammalian host species, but the risks to public health from wildlife are poorly understood. In summer 2008, the Cryptosporidium sp. rabbit genotype was identified as the aetiological agent in an outbreak of waterborne human cryptosporidiosis. The source was a wild rabbit that had entered a treated water tank. To establish current knowledge about Cryptosporidium spp. infecting lagomorphs, especially the host range and biological characteristics of the rabbit genotype, and the potential risks to public health that rabbits may pose in the transmission of zoonotic cryptosporidiosis, we undertook a literature and data review. The literature returned demonstrates that although the European rabbit (Oryctolagus cuniculus) has been the most widely studied lagomorph, few large scale studies were found. The prevalence of Cryptosporidium spp. in wild rabbit populations in the two large scale studies was 0.9% (95%CI 0.2-5.0) and 0.0% (95%CI 0.0-1.6). Neither study provided age nor sex profiles nor typing of Cryptosporidium isolates. The infecting Cryptosporidium species was confirmed in just four other studies of rabbits, all of which showed the rabbit genotype. Human-infectious Cryptosporidium species including Cryptosporidium parvum have caused experimental infections in rabbits and it is likely that this may also occur naturally. No published studies of the host range and biological features of the Cryptosporidium rabbit genotype were identified, but information was generated on the identification and differentiation of the rabbit genotype at various genetic loci. Both pet and wild rabbits are a potential source of human cryptosporidiosis and as such, good hygiene practices are recommended during and after handling rabbits or exposure to their faeces, or potentially contaminated surfaces. Water supplies should be protected against access by wildlife, including rabbits.

Microsystems for the capture of low-abundance cells

Efficient selection and enumeration of low-abundance biological cells are highly important in a variety of applications. For example, the clinical utility of circulating tumor cells (CTCs) in peripheral blood is recognized as a viable biomarker for the management of various cancers, in which the clinically relevant number of CTCs per 7.5 ml of blood is two to five. Although there are several methods for isolating rare cells from a variety of heterogeneous samples, such as immunomagnetic-assisted cell sorting and fluorescence-activated cell sorting, they are fraught with challenges. Microsystem-based technologies are providing new opportunities for selecting and isolating rare cells from complex, heterogeneous samples. Such approaches involve reductions in target-cell loss, process automation, and minimization of contamination issues. In this review, we introduce different application areas requiring rare cell analysis, conventional techniques for their selection, and finally microsystem approaches for low-abundance-cell isolation and enumeration.

Surface-enhanced resonance raman spectroscopy for the rapid detection of Cryptosporidium parvum and Giardia lamblia

A rapid surface-enhanced resonance Raman spectroscopy (SERRS) method has been developed for the detection of two waterborne pathogens, Cryptosporidium parvum and Giardia lambia. Raman labels were prepared by conjugating gold nanoparticles with commercial antibodies and dye molecules. After incubation with the immunogold labels, C. parvum oocysts and G. lamblia could easily be measured and differentiated by Raman spectroscopy. The immunogold signal intensities were optimized by testing several sizes of gold nanoparticles, four different commercially available dye molecules, and two Raman excitation wavelengths. Raman maps were collected across fixed and labeled Cryptosporidium oocysts and Giardia cysts, and the maps were used to determine which C. parvum and G. lamblia antibodies exhibited the best specificities and organism coverages. Ultimately, 40 nm gold nanoparticles were conjugated with rhodamine B isothiocyanate and malachite green isothiocyanate for the C. parvum and G. lamblia immunogold syntheses, respectively. C. parvum monoclonal IgM antibodies and G. lamblia monoclonal IgG1 antibodies resulted in the best immunogold coverage. The research presented here demonstrates the feasibility of utilizing SERRS labeling for sensitive multipathogen monitoring strategies.

Detection and surveillance of waterborne protozoan parasites

The majority of the world's population still live without access to healthy water and the contamination of drinking water with protozoan pathogens poses a serious threat to millions of people in the developing world. Even in the developed world periodic outbreaks of diarrhoeal diseases are caused by the protozoan parasites Cryptosporidium sp., Giardia duodenalis and Entamoeba histolytica. Thus, surveillance of drinking water is imperative to minimize such contaminations and ensure continuous supplies of healthy water world-wide. This article reviews the progress in technology for detection and surveillance of these important waterborne parasites.

Methods in cell separations

Research in the field of cell biology and biomedicine relies on technologies that fractionate cell populations and isolate rare cell types to high purity. A brief overview of methods and commercially available products currently used in cell separations is presented. Cell fractionation by size and density and highly selective affinity-based technologies such as affinity chromatography, fluorescence-activated cell sorting (FACS) and magnetic cell sorting are discussed in terms of throughput, yield, and purity.

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.

Quantitative-PCR assessment of Cryptosporidium parvum cell culture infection

A quantitative TaqMan PCR method was developed for assessing the Cryptosporidium parvum infection of in vitro cultivated human ileocecal adenocarcinoma (HCT-8) cell cultures. This method, termed cell culture quantitative sequence detection (CC-QSD), has numerous applications, several of which are presented. CC-QSD was used to investigate parasite infection in cell culture over time, the effects of oocyst treatment on infectivity and infectivity assessment of different C. parvum isolates. CC-QSD revealed that cell culture infection at 24 and 48 h postinoculation was approximately 20 and 60%, respectively, of the endpoint 72-h postinoculation infection. Evaluation of three different lots of C. parvum Iowa isolate oocysts revealed that the mean infection of 0.1 N HCl-treated oocysts was only 36% of the infection obtained with oocysts treated with acidified Hanks' balanced salt solution containing 1% trypsin. CC-QSD comparison of the C. parvum Iowa and TAMU isolates revealed significantly higher levels of infection for the TAMU isolate, which agrees with and supports previous human, animal, and cell culture studies. CC-QSD has the potential to aid in the optimization of Cryptosporidium cell culture methods and facilitate quantitative evaluation of cell culture infectivity experiments.

Concentrating, purifying and detecting waterborne parasites

There has been recent emphasis on developing better methods for detecting diseases of zoonotic and veterinary importance. This has been prompted by an increase in human disease agents detectable in environmental samples, the potential for bioterrorism, and the lowering of international trade barriers and expansion of personal travel, which are bringing previously considered exotic diseases to new geographical localities. To appreciate the complexities of developing detection methods and working with environmental samples, it is appropriate to review technologies currently in use, as well as those in development and presently limited to research laboratories. Discussion of parasite detection would not be possible without including methods for parasite sampling, concentration, and purification because it is often necessary to process large sample volumes prior to analysis, and no reliable methods are available for significantly amplifying parasites in vitro. Reviewing proven methods currently in use will provide a baseline for generating, accepting and implementing the more sensitive and specific methods under development today.

Optimization of DNA extraction and molecular detection of Cryptosporidium oocysts in natural mineral water sources

The numerous published methods for extracting DNA from Cryptosporidium oocysts for PCR identify the lack of an optimized standard method for clinical, environmental, and public health investigations of cryptosporidiosis. A method that maximizes DNA extraction reliably, particularly from small numbers of partially purified or purified oocysts present in mineral waters and environmental samples, is required. We describe a maximized method for liberating DNA from Cryptosporidium parvum oocysts by 15 cycles of freezing (liquid nitrogen) and thawing (65 degrees C) in lysis buffer containing sodium dodecyl sulfate. The inhibitory effects of sodium dodecyl sulfate are abrogated by the addition of Tween 20 to the PCR reaction. We tested seven different C. parvum oocyst isolates, consistently detecting fewer than five oocysts following direct PCR amplification of a segment of the 18S rRNA gene. Older oocysts, which were more refractory to freeze-thawing, were disrupted effectively. A single oocyst in each of two mineral water concentrates was detected by both microscopy and PCR/Southern blotting. We recommend 15 cycles of freeze-thawing, with thawing at 65 degrees C in lysis buffer, to maximize oocyst disruption and DNA extraction, particularly when isolate history and oocyst age are unknown. Both the DNA extraction method and the PCR described can be used for clinical, environmental, and public health investigations of cryptosporidiosis.

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.

Towards a unified system for detecting waterborne pathogens

Currently, there is no single method to collect, process, and analyze a water sample for all pathogenic microorganisms of interest. Some of the difficulties in developing a universal method include the physical differences between the major pathogen groups (viruses, bacteria, protozoa), efficiently concentrating large volume water samples to detect low target concentrations of certain pathogen groups, removing co-concentrated inhibitors from the sample, and standardizing a culture-independent endpoint detection method. Integrating the disparate technologies into a single, universal, simple method and detection system would represent a significant advance in public health and microbiological water quality analysis. Recent advances in sample collection, on-line sample processing and purification, and DNA microarray technologies may form the basis of a universal method to detect known and emerging waterborne pathogens. This review discusses some of the challenges in developing a universal pathogen detection method, current technology that may be employed to overcome these challenges, and the remaining needs for developing an integrated pathogen detection and monitoring system for source or finished water.

Evaluation of a combined immunomagnetic separation/flow cytometry technique for epidemiological investigations of Cryptosporidium in domestic and Australian native animals

A combined immunomagnetic separation (IMS) and flow cytometry (FC) technique was developed for the sensitive detection of Cryptosporidium in faecal samples. The IMS/FC technique was found to be approximately 50-fold more sensitive than formol-ether concentration, which is commonly used for Cryptosporidium epidemiological investigations. Of 31 faecal samples from captive animals 16 were found to contain Cryptosporidium oocysts when analysed using the IMS/FC compared to four when using formol-ether concentration (FEC). In a wild population of eastern grey kangaroos Macropus giganteus 66.3% of infected animals were shedding <500oocysts/gfaeces when analysed using IMS/FC. This is below the detection limit for the FEC method. The dispersal of Cryptosporidium in host populations is aggregated, with many individuals shedding low numbers of oocysts and few individuals shedding numbers of oocysts sufficiently high to be detected by FEC. This research demonstrates that the prevalence and oocyst shedding intensity of Cryptosporidium in animal populations will be significantly underestimated using standard detection methods.

Emerging waterborne infections: contributing factors, agents, and detection tools

Because microorganisms are easily dispersed, display physiological diversity, and tolerate extreme conditions, they are ubiquitous and may contaminate and grow in water. The presence of waterborne enteric pathogens (bacteria, viruses, and protozoa) in domestic water supplies represents a potentially significant human health risk. Even though major outbreaks of waterborne disease are comparatively rare, there is substantial evidence that human enteric pathogens that are frequently present in domestic water supplies are responsible for low-level incidence of waterborne microbial disease. Although these diseases are rarely debilitating to healthy adults for more than a few hours to a few days, enteric pathogens can cause severe illness, even death, for young children, the elderly, or those with compromised immune systems. As the epidemiology of waterborne diseases is changing, there is a growing global public health concern about new and reemerging infectious diseases that are occurring through a complex interaction of social, economic, evolutionary, and ecological factors. New microbial pathogens have emerged, and some have spread worldwide. Alternative testing strategies for waterborne diseases should significantly improve the ability to detect and control the causative pathogenic agents. In this article, we provide an overview of the current state of knowledge of waterborne microbial pathogens, their detection, and the future of new methods in controlling these infectious agents.

Detection and genotyping of oocysts of Cryptosporidium parvum by real-time PCR and melting curve analysis

Several real-time PCR procedures for the detection and genotyping of oocysts of Cryptosporidium parvum were evaluated. A 40-cycle amplification of a 157-bp fragment from the C. parvum beta-tubulin gene detected individual oocysts which were introduced into the reaction mixture by micromanipulation. SYBR Green I melting curve analysis was used to confirm the specificity of the method when DNA extracted from fecal samples spiked with oocysts was analyzed. Because C. parvum isolates infecting humans comprise two distinct genotypes, designated type 1 and type 2, real-time PCR methods for discriminating C. parvum genotypes were developed. The first method used the same beta-tubulin amplification primers and two fluorescently labeled antisense oligonucleotide probes spanning a 49-bp polymorphic sequence diagnostic for C. parvum type 1 and type 2. The second genotyping method used SYBR Green I fluorescence and targeted a polymorphic coding region within the GP900/poly(T) gene. Both methods discriminated between type 1 and type 2 C. parvum on the basis of melting curve analysis. To our knowledge, this is the first report describing the application of melting curve analysis for genotyping of C. parvum oocysts.

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.

PCR-restriction fragment length polymorphism analysis of a diagnostic 452-base-pair DNA fragment discriminates between Cryptosporidium parvum and C. meleagridis and between C. parvum isolates of human and animal origin

Genomic DNAs from human Cryptosporidium isolates previously typed by analysis of the 18S ribosomal DNA locus (Cryptosporidium parvum bovine genotype, C. parvum human genotype, Cryptosporidium meleagridis, and Cryptosporidium felis) were used to amplify the diagnostic fragment described by Laxer et al. (M. A. Laxer, B. K. Timblin, and R. J. Patel, Am. J. Trop. Med. Hyg., 45:688-694, 1991). The obtained 452-bp amplified fragments were sequenced and aligned with the homologous Cryptosporidium wrairi sequence. Polymorphism was exploited to develop a restriction fragment length polymorphism method able to discriminate Cryptosporidium species and C. parvum genotypes.

Simultaneous detection of Cryptosporidium parvum and Giardia in sewage sludge by IC-PCR

AIMS

The aim of this study was to develop a method based on immunomagnetic capture and polymerase chain reaction (IC-PCR assay) for detection of Cryptosporidium parvum and Giardia intestinalis in sewage sludge.

METHODS AND RESULTS

The detection limit of the IC-PCR assay for both organisms was 625 oocysts and cysts ml(-1). By hybridization of PCR products the sensitivity could be increased to 125 oocysts and cysts ml(-1). Forty-four sludge samples from 12 wastewater treatment plants were examined. The samples positive for Giardia (9 out of 44) were from eight wastewater plants and the C. parvum genotype 2 samples (3 out of 44) originated from different sewage works.

CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY

IC-PCR offers the possibility to distinguish between Cryptosporidium and Giardia genotypes. This assay can be used to monitor the presence of these organisms in a community and to determine contamination of sludge used as soil amendment.

Species-specific, nested PCR-restriction fragment length polymorphism detection of single Cryptosporidium parvum oocysts

Concurrent with recent advances seen with Cryptosporidium parvum detection in both treated and untreated water is the need to properly evaluate these advances. A micromanipulation method by which known numbers of C. parvum oocysts, even a single oocyst, can be delivered to a test matrix for detection sensitivity is presented. Using newly developed nested PCR-restriction fragment length polymorphism primers, PCR sensitivity was evaluated with 1, 2, 3, 4, 5, 7, or 10 oocysts. PCR detection rates (50 samples for each number of oocysts) ranged from 38% for single oocysts to 92% for 5 oocysts, while 10 oocysts were needed to achieve 100% detection. The nested PCR conditions amplified products from C. parvum, Cryptosporidium baileyi, and Cryptosporidium serpentis but no other Cryptosporidium sp. or protozoan tested. Restriction enzyme digestion with VspI distinguished between C. parvum genotypes 1 and 2. Restriction enzyme digestion with DraII distinguished C. parvum from C. baileyi and C. serpentis. Use of known numbers of whole oocysts encompasses the difficulty of liberating DNA from the oocyst and eliminates the standard deviation inherent within a dilution series. To our knowledge this is the first report in which singly isolated C. parvum oocysts were used to evaluate PCR sensitivity. This achievement illustrates that PCR amplification of a single oocyst is feasible, yet sensitivity remains an issue, thereby illustrating the difficulty of dealing with low oocyst numbers when working with environmental water samples.

Estimating viability of Cryptosporidium parvum oocysts using reverse transcriptase-polymerase chain reaction (RT-PCR) directed at mRNA encoding amyloglucosidase

The purpose of the present study was to determine if reverse transcriptase-polymerase chain reaction (RT-PCR) directed at mRNA encoding the enzyme amyloglucosidase (CPAG) could serve as a indicator for C. parvum oocyst viability. Oocysts were stored for 1-11 months in the refrigerator and at monthly intervals extracted for total RNA for RT-PCR analysis. An aliquot of these C. parvum oocysts was inoculated into neonatal mice which were necropsied 4 days later for ileal tissue that was analyzed by semi-quantitative PCR to determine the level of parasite replication. The CPAG RT-PCR assay detected RNA from as few as 10(3) C. parvum oocysts. An effect of storage time on both RT-PCR signal and mouse infectivity was observed. RNA from oocysts stored for 1-7 months, unlike oocysts stored for 9 or 11 months, contained CPAG mRNA that was detectable by RT-PCR. A gradual decrease in the RT-PCR signal intensity was observed between 5 and 7 months storage. The intensity of RT-PCR product from oocysts and the signal from semi-quantitative PCR of ileal tissue DNA from mice infected with these same aged oocysts were comparable. The RT-PCR assay of CPAG mRNA in cultured cells infected with viable C. parvum oocysts first detected expression at 12 h with highest expression levels observed at 48 h post-infection. These results indicate that CPAG RT-PCR may be useful for differentiating viable from non-viable C. parvum oocysts and for studying the expression of the gene for amyloglucosidase in vitro.

Development of a novel, rapid integrated Cryptosporidium parvum detection assay

The aim of this study was to develop a reverse transcription-PCR assay and lateral flow detection protocol for specific identification of Cryptosporidium parvum. The method which we developed is sensitive and specific and has a low limit of detection. In our protocol a solid phase material, the Xtra Bind Capture System, was used for extraction and purification of double-stranded RNA (dsRNA) specific for C. parvum. The Xtra Bind Capture System interfaced with pellets concentrated from water samples collected with previously developed filtration devices. The pellets were resuspended in reagent water (final volume, 0.5 ml), and an equal amount of rupture buffer and the Xtra Bind Capture System was added to the resuspended pellet mixture. The dsRNA target sequences in a 0. 5-ml portion were captured by the solid phase material via hybridization. The debris and potential inhibitors were removed by washing the Xtra Bind material several times with buffer. The Xtra Bind material with its bound dsRNA was added directly to an amplification reaction mixture, and the target was amplified without elution from the Xtra Bind material. A PCR was performed in the presence of the Xtra Bind Capture System, which resulted in robust amplification of the target. The detection system which we used was adapted from lateral flow chromatography methods typically used for antigen-antibody reactions. The result was a colored line that was visible if the organism was present. When this method was used, we were able to reproducibly and correctly identify 10 oocysts added to 0.5 ml of reagent water. When the protocol was evaluated with a small set of environmental samples, the level of detection was as low as 1 oocyst/liter. The total time from resuspension of the pellet to detection was about 3 h, which is considerably less than the 5 h required for immunomagnetic separation followed by an indirect immunofluorescence assay and microscopy.

Comparative detection of Cryptosporidium parvum oocysts from apple juice

Drinking unpasteurized apple juice (or cider) has been associated with cryptosporidiosis, the diarrheal disease caused by the small protozoan parasite, Cryptosporidium parvum. This report compares detection of C. parvum oocysts from apple juice by acid-fast staining (AFS), direct immunofluorescence assay (DIFA), and polymerase chain reaction (PCR), following sample concentration by formalin-ethyl acetate sedimentation or sucrose flotation. Flotation was more efficient than sedimentation in recovering oocysts, and DIFA consistently detected lower numbers of oocysts than AFS. In combination, flotation-AFS could detect 3000 to 10,000 oocysts inoculated into 100 ml of apple juice while flotation-DIFA was able to detect as few as 100 oocysts. The highest sensitivity, 10 to 30 oocysts per 100 ml of apple juice, was achieved by DIFA following immunomagnetic capture (IC) of oocysts from samples concentrated by the flotation method. The detection limit of PCR following flotation or flotation IC was 30 to 100 oocysts; sequence analysis of the amplicon demonstrated that the PCR amplicon was C. parvum-specific.

Immunomagnetic separation of Cryptosporidium parvum oocysts using MACS MicroBeads and high gradient separation columns

We evaluated the MACS immunomagnetic separation (IMS) system for concentrating Cryptosporidium parvum. Oocysts were first labeled with fluorescein isothiocyanate (FITC) or rabbit anti-C. parvum antibodies, then linked to MicroBeads coated with anti-FITC or anti-rabbit IgG, and separated through a high gradient separation column. Results indicated that over 95% of oocysts were recovered and their fluorescence and infectivity were retained. The presence of MicroBeads showed no effect on genomic DNA extraction and subsequent polymerase chain reaction (PCR)-based analyses, as sensitivity of PCR (10 oocysts) and the band pattern of randomly amplified polymorphic DNA (RAPD) were identical to those using DNAs extracted from normally purified oocysts. IMS-PCR consistently detected as few as 10 oocysts from 100 ml of apple juice or homogenized milk and IMS-IFA could detect 100 oocysts from 1 g of deer manure, demonstrating the efficiency of IMS in recovering oocysts from environmental and food samples. Our results suggest that the MACS IMS system could be used for multiple applications in Cryptosporidium research.

Rapid DNA extraction methods and new primers for randomly amplified polymorphic DNA analysis of Giardia duodenalis

A randomly amplified polymorphic DNA (RAPD) procedure using simple genomic DNA preparation methods and newly designed primers was optimized for analyzing Giardia duodenalis strains. Genomic DNA was extracted from in vitro cultivated trophozoites by five freezing-thawing cycles or by sonic treatment. Compared to a conventional method involving proteinase K digestion and phenol extraction, both freezing-thawing and sonication were equally efficient, yet with the advantage of being much less time- and labor-intensive. Five of the 10 tested RAPD primers produced reproducible polymorphisms among five human origin G. duodenalis strains, and grouping of these strains based on RAPD profiles was in agreement among these primers. The consistent classification of two standard laboratory reference strains, Portland-1 and WB, in the same group confirmed previous results using other fingerprinting methods, indicating that the reported simple DNA extraction methods and the selected primers are useful in RAPD for molecular characterization of G. duodenalis strains.

Detection of infectious Cryptosporidium parvum oocysts in surface and filter backwash water samples by immunomagnetic separation and integrated cell culture-PCR

A new strategy for the detection of infectious Cryptosporidium parvum oocysts in water samples, which combines immunomagnetic separation (IMS) for recovery of oocysts with in vitro cell culturing and PCR (CC-PCR), was field tested with a total of 122 raw source water samples and 121 filter backwash water grab samples obtained from 25 sites in the United States. In addition, samples were processed by Percoll-sucrose flotation and oocysts were detected by an immunofluorescence assay (IFA) as a baseline method. Samples of different water quality were seeded with viable C. parvum to evaluate oocyst recovery efficiencies and the performance of the CC-PCR protocol. Mean method oocyst recoveries, including concentration of seeded 10-liter samples, from raw water were 26.1% for IMS and 16.6% for flotation, while recoveries from seeded filter backwash water were 9.1 and 5.8%, respectively. There was full agreement between IFA oocyst counts of IMS-purified seeded samples and CC-PCR results. In natural samples, CC-PCR detected infectious C. parvum in 4.9% (6) of the raw water samples and 7.4% (9) of the filter backwash water samples, while IFA detected oocysts in 13.1% (16) of the raw water samples and 5.8% (7) of the filter backwash water samples. All CC-PCR products were confirmed by cloning and DNA sequence analysis and were greater than 98% homologous to the C. parvum KSU-1 hsp70 gene product. DNA sequence analysis also revealed reproducible nucleotide substitutions among the hsp70 fragments, suggesting that several different strains of infectious C. parvum were detected.

Comparison of sensitivity of immunofluorescent microscopy to that of a combination of immunofluorescent microscopy and immunomagnetic separation for detection of Cryptosporidium parvum oocysts in adult bovine feces

A direct immunofluorescence assay (DFA) (Merifluor; Meridian Diagnostics, Inc., Cincinnati, Ohio) was compared to an immunomagnetic separation (IMS) assay (Dynabeads; Dynal, Inc., Lake Success, N.Y.) coupled with immunofluorescent microscopy (Waterborne, Inc., New Orleans, La.) for their ability to detect low concentrations of Cryptosporidium parvum oocysts in adult bovine fecal material. IMS-DFA resulted in a 2-log-unit increase in sensitivity (10 oocysts/g) compared to DFA alone (1,000 oocysts/g). The higher sensitivity obtained with IMS-DFA resulted from testing 2 g of fecal material instead of the 13 to 19 mg of fecal material tested in the DFA; the increased sensitivity was not attributable to a higher percent recovery.

Cryptosporidium parvum studies with dairy products

Cryptosporidium parvum is a protozoan parasite capable of causing massive waterborne outbreaks. This study was conducted to model the transfer of C. parvum oocysts from contaminated water via food contact surfaces into yogurt and ice-cream, as well as to examine oocyst survival. Propidium iodide staining, combined with a direct immunofluorescence assay, was used for oocyst viability determination. Oocysts were recovered from milk products by a sucrose flotation-based procedure, with average recoveries of 82.3, 60.7, and 62.5% from low (1%) fat milk, 9% fat ice-cream, and 98% fat-free yogurt, respectively. Oocysts were also recovered, by rinsing with tap water, from stainless steel surfaces inoculated with oocyst suspension, with average recoveries of 93.1% when the surface was still wet and 69.0% after the surface had air-dried at room temperature. Viability of oocysts on the surface was significantly affected by desiccation; 5% of the oocysts remained viable after 4 h of air-drying at room temperature, while the proportion of viable oocysts was 81, 69, and 45% after air-drying for 10 min, 1 h, and 2 h, respectively. In contrast, oocyst viability only dropped from 82 to 75% after 30 min contact at room temperature with 5% bleach solution (equivalent to 0.26% NaOCl). Transfer of oocysts from milk and stainless steel surfaces into yogurt, and oocyst survival during the process were analyzed. Yogurt was made from pasteurized low fat milk and live yogurt starter by incubating at 37 degrees C for 48 h and then stored at 4 degrees C. Oocyst viability decreased from 83% (80%) to approximately 60% after 48 h at 37 degrees C and to approximately 58% following 8 days of storage, similar to oocyst survival in the controls using pasteurized milk without the addition of live yogurt. Oocyst survival in ice-cream was investigated by inoculating oocysts into ice-cream mix, and mixing and freezing in an ice-cream freezer, and hardening at -20 degrees C. Although approximately 20% (25 and 18%) of oocysts were viable before hardening, none were viable after 24 h at -20 degrees C. Control samples of oocysts suspended in distilled water and stored at -20 degrees C were taken at the same time intervals and 8% of the oocysts were still viable after 24 h.

Evaluation of immunomagnetic separation for recovery of infectious Cryptosporidium parvum oocysts from environmental samples

Two commercial immunomagnetic separation (IMS) kits for Cryptosporidium were compared for recovery of oocysts from environmental samples. Oocyst recovery efficiencies with the Dynal and Crypto-Scan kits ranged from 62 to 100% and 34 to 74%, respectively, for seeded environmental water concentrates (turbidity of 210 to 11,480 nephelometric turbidity units). Recovery efficiencies were dependent on the mechanism of agitation during the magnetic capture procedure. An assay combining in vitro cell culture and reverse transcriptase PCR demonstrated that oocysts recovered by IMS retained their infectivity.

Immunomagnetic separation of Cryptosporidium parvum from source water samples of various turbidities

Immunomagnetic separation (IMS) procedures which specifically capture Cryptosporidium oocysts and have the potential to isolate oocysts from debris have become commercially available. We compared two IMS kits (kit DB [Dynabeads anti-Cryptosporidium; product no. 730.01; Dynal A.S., Oslo, Norway] and kit IC1 [Crypto Scan IMS; product no. R10; Clearwater Diagnostics Company, LLC, Portland, Maine]) and a modification of kit IC1 (kit IC2 [Crypto Scan IMS; product no. R10; Clearwater Diagnostics Company, LLC]) at three turbidity levels (50, 500, and 5,000 nephelometric turbidity units [ntu]) by using water matrices obtained from different geographical locations. In deionized water, kit DB yielded recoveries between 68 and 83%, whereas the recoveries obtained with kits IC1 and IC2 were more variable and ranged from 0.2 to 74.5%. In water matrices with turbidity levels up to 500 ntu, the oocyst recoveries were more variable with kit DB; however, the recoveries were similar to those obtained in deionized water. In contrast, there were notable reductions in oocyst recoveries in the turbid matrices with kits IC1 and IC2, and the highest recovery (8.3%) was obtained with a 50-ntu sample. An examination of the effects of age on oocyst recovery with kit DB revealed that oocysts up to 16 weeks old yielded recoveries similar to the recoveries observed with fresh oocysts. These data indicate that all IMS kits do not perform equally well, and it is important to conduct in-house quality assurance work before a commercially available IMS kit is selected to replace flotation procedures for recovery of Cryptosporidium oocysts.

Differentiation of Cryptosporidium parvum isolates by a simplified randomly amplified polymorphic DNA technique

Genomic DNA was isolated from Cryptosporidium parvum oocysts by a specific immunomagnetic separation-in vitro excystation procedure and subjected to randomly amplified polymorphic DNA analysis using sequence-independent primers. An estuary C. parvum isolate was easily differentiated from several bovine isolates, while five bovine isolates of the same origin were indistinguishable from each other.

Sensitive and rapid detection of viable Giardia cysts and Cryptosporidium parvum oocysts in large-volume water samples with wound fiberglass cartridge filters and reverse transcription-PCR

We recently described a reverse transcription-PCR (RT-PCR) for detecting low numbers of viable Cryptosporidium parvum oocysts spiked into clarified environmental water concentrates. We have now modified the assay for direct analysis of primary sample concentrates with simultaneous detection of viable C. parvum oocysts, Giardia cysts, and a novel type of internal positive control (IPC). The IPC was designed to assess both efficiency of mRNA isolation and potential RT-PCR inhibition. Sensitivity testing showed that low numbers of organisms, in the range of a single viable cyst and oocyst, could be detected when spiked into 100-microliter packed pellet volumes of concentrates from creek and river water samples. The RT-PCR was compared with an immunofluorescence (IF) assay by analyzing 29 nonspiked environmental water samples. Sample volumes of 20 to 1,500 liters were concentrated with a wound fiberglass cartridge filter. Frequency of detection for viable Giardia cysts increased from 24% by IF microscopy to 69% by RT-PCR. Viable C. parvum oocysts were detected only once by RT-PCR (3%) in contrast to detection of viable Cryptosporidium spp. in four samples by IF microscopy (14%), suggesting that Cryptosporidium species other than C. parvum were present in the water. This combination of the large-volume sampling method with RT-PCR represents a significant advance in terms of protozoan pathogen monitoring and in the wider application of PCR technology to this field of microbiology.

Immunomagnetic capture PCR for rapid concentration and detection of hepatitis A virus from environmental samples

We studied the concentration of hepatitis A virus (HAV) from environmental samples by membrane filter-based urea-arginine phosphate buffer and its detection by using immunomagnetic capture (IC) reverse transcription (RT)-PCR (IC PCR). Magnetic beads coated with anti-HAV rabbit antibodies were used for enrichment and concentration of HAV from environmental samples. IC PCR is sensitive enough to detect as few as 0.04 PFU of cell culture-adapted HAV in inoculated water and sewage samples. IC PCR is specific and does not yield positive reactions with poliovirus 1, HAV RNA, or selected bacteriophages. IC concentrates viruses suspended in small volumes to microliter volumes that can be used directly in RT-PCR. IC concentration of viruses from sewage samples without concentration of inhibitory substances is important for successful RT-PCR detection. In a field trial, 2 of 18 raw sewage samples tested by IC PCR were positive for HAV.

Development of a PCR protocol for sensitive detection of Cryptosporidium oocysts in water samples

The development of a reliable method of using PCR for detection of Cryptosporidium oocysts in environmental samples with oligonucleotide primers which amplify a portion of the sequence encoding the small (18S) subunit of rRNA producing a 435-bp product was demonstrated. The PCR assay was found to provide highly genus-specific detection of Cryptosporidium spp. after release of nucleic acids from oocysts by a simple freeze-thaw procedure. The assay routinely detected 1 to 10 oocysts in purified oocyst preparations, as shown by direct microscopic counts and by an immunofluorescence assay. The sensitivity of the PCR assay in some seeded environmental water samples was up to 1,000-fold lower. However, this interference was eliminated by either flow cytometry or magnetic-antibody capture. Sensitivity was also improved 10- to 1,000-fold by probing of the PCR product on dot blots with an oligonucleotide probe detected by chemiluminescence. Confirmation of the presence of Cryptosporidium oocysts in water samples from the outbreak in Milwaukee, Wis., was obtained with this technique, and PCR was found to be as sensitive as immunofluorescence for detection of oocysts in wastewater concentrates.