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

Detection of Cryptosporidium spp. and Giardia spp. in Environmental Water Samples: A Journey into the Past and New Perspectives

Among the major issues linked with producing safe water for consumption is the presence of the parasitic protozoa Cryptosporidium spp. and Giardia spp. Since they are both responsible for gastrointestinal illnesses that can be waterborne, their monitoring is crucial, especially in water sources feeding treatment plants. Although their discovery was made in the early 1900s and even before, it was only in 1999 that the U.S. Environmental Protection Agency (EPA) published a standardized protocol for the detection of these parasites, modified and named today the U.S. EPA 1623.1 Method. It involves the flow-through filtration of a large volume of the water of interest, the elution of the biological material retained on the filter, the purification of the (oo)cysts, and the detection by immunofluorescence of the target parasites. Since the 1990s, several molecular-biology-based techniques were also developed to detect Cryptosporidium and Giardia cells from environmental or clinical samples. The application of U.S. EPA 1623.1 as well as numerous biomolecular methods are reviewed in this article, and their advantages and disadvantages are discussed guiding the readers, such as graduate students, researchers, drinking water managers, epidemiologists, and public health specialists, through the ever-expanding number of techniques available in the literature for the detection of Cryptosporidium spp. and Giardia spp. in water.

Whatman Protein Saver Cards for Storage and Detection of Parasitic Enteropathogens

Current methods to identify the etiology of diarrhea require laboratory facilities for storage of pathogens, which is often challenging in low-resource settings. This study evaluated the efficacy of a low-cost method for preserving stool specimens for the detection of parasitic enteropathogens using Whatman 903 protein saver cards (Sigma-Aldrich, St. Louis, MO). Stool samples known to be positive by multiplex real-time polymerase chain reaction for Giardia lamblia, Cryptosporidium spp., and Entamoeba histolytica parasites were preserved on 232 Whatman cards. DNA was then extracted from cards using Chelex and Qiagen extraction protocols, and tested for these parasites using multiplex real-time PCR. We included stool samples known to have a higher parasite load (cycle threshold [ct]-value < 30) and those with a lower parasite load (ct values 30-35). Sensitivities and specificities were determined using DNA extracted directly from whole stool samples using Qiagen kits (QIAGEN, Hilden, Germany). For whole stool samples with ct values < 30, preserved directly on Whatman 903 protein saver cards for Giardia analysis, the sensitivity was 100% for both Qiagen and Chelex DNA extraction. For E. histolytica, this was 100% for sensitivity for Qiagen and 80% for Chelex DNA extractions, and for Cryptosporidium, this was 80% for Qiagen and 50% for Chelex DNA extraction. The specificity was 100% for all parasites for all extraction procedures. Given the high sensitivity for stool samples with higher parasite loads, we recommend the use of the Whatman 903 protein saver card for preserving fecal specimens for the analysis of Giardia and E. histolytica using Qiagen DNA extractions in low-resource settings.

Cryptosporidium Oocyst Contamination in Drinking Water: A Case Study in Italy

The aim of this study was to evaluate the occurrence of Cryptosporidium oocysts in a drinking water treatment plant (DWTP) located in a rural area of northern Italy. Influent and effluent samples were collected at the DWTP over three years (2013-2016). In parallel, tap water samples from a public drinking fountain were collected as well. All samples were analyzed for the presence of Cryptosporidium spp. oocysts by a common method based on an immunomagnetic separation (IMS)/immunofluorescence assay (IFA), complemented by 4,6-diamidino-2-phenylindole (DAPI) staining. A reverse transcriptase-PCR (RT-PCR) protocol was added to evaluate oocyst viability. The results highlighted a high variability of oocyst concentrations across all samples (mean 4.3 ± 5.8/100 L) and a high variability in the percentage of DAPI-positive specimens (mean 48.2% ± 40.3%). Conversely, RT-PCR did not reveal the presence of viable C. parvum and C. hominis oocysts. A nested PCR targeting Cryptosporidium 18S ribosomal DNA, carried out in two water samples, confirmed the presence of a Cryptosporidium genotype associated with wild animals in the river and in tap water. The results obtained underline the vulnerability of the investigated surface water to Cryptosporidium spp. contamination. Although the recovered Cryptosporidium genotype is not a human pathogen, its presence demonstrates the existence of a potential pathogen Cryptosporidium spp. contamination risk. Moreover, these results underline the importance of also considering unconventional (not bacterial) biological contaminations (protozoa) in water resources in rural areas, including those of developed countries.

Development of Species-specific rDNA Probes for Giardia by Multiple Fluorescent In Situ Hybridization Combined with Immunocytochemical Identification of Cyst Wall Antigens

In this study, we describe the development of fluorescent oligonucleotide probes to variable regions in the small subunit of 16S rRNA in three distinct Giardia species. Sense and antisense probes (17–22 mer) to variable regions 1, 3, and 8 were labeled with digoxygenin or selected fluorochomes (FluorX, Cy3, or Cy5). Optimal results were obtained with fluorochome-labeled oligonucleotides for detection of rRNA in Giardia cysts. Specificity of fluorescent in situ hybridization (FISH) was shown using RNase digestion and high stringency to diminish the hybridization signal, and oligonucleotide probes for rRNA in Giardia lamblia, Giardia muris, and Giardia ardeae were shown to specifically stain rRNA only within cysts or trophozoites of those species. The fluorescent oligonucleotide specific for rRNA in human isolates of Giardia was positive for ten different strains. A method for simultaneous FISH detection of cysts using fluorescent antibody (genotype marker) and two oligonucleotide probes (species marker) permitted visualization of G. lamblia and G. muris cysts in the same preparation. Testing of an environmental water sample revealed the presence of FISH-positive G. lamblia cysts with a specific rDNA probe for rRNA, while negative cysts were presumed to be of animal or bird origin.

Presence of Cryptosporidium parvum and Giardia lamblia in water samples from Southeast Asia: towards an integrated water detection system

Background

Access to clean and safe drinking water that is free from pathogenic protozoan parasites, especially Cryptosporidium parvum and Giardia lamblia that cause gastrointestinal illness in humans, is still an issue in Southeast Asia (SEA). This study is the first attempt to detect the aforementioned protozoan parasites in water samples from countries in SEA, using real-time polymerase chain reaction (qPCR) assays.

Methods

A total of 221 water samples of 10 l each were collected between April and October 2013 from Malaysia (53), Thailand (120), the Philippines (33), and Vietnam (15). A physicochemical analysis was conducted. The water samples were processed in accordance with the US Environmental Protection Agency’s methods 1622/1623.1, microscopically observed and subsequently screened using qPCR assays.

Results

Cryptosporidium oocysts were detected in treated water samples from the Philippines (1/10), with a concentration of 0.06 ± 0.19 oocyst/L, and untreated water samples from Thailand (25/93), Malaysia (17/44), and the Philippines (11/23), with concentrations ranging from 0.13 ± 0.18 to 0.57 ± 1.41 oocyst/L. Giardia cysts were found in treated water samples from the Philippines (1/10), with a concentration of 0.02 ± 0.06 cyst/L, and in untreated water samples from Thailand (20/93), Vietnam (5/10), Malaysia (22/44), and the Philippines (16/23), with concentrations ranging from 0.12 ± 0.3 to 8.90 ± 19.65 cyst/L. The pathogens C. parvum and G. lamblia were detected using using qPCR assays by targeting the 138-bp fragment and the small subunit gene, respectively. C. parvum was detected in untreated water samples from the Philippines (1/23) and Malaysia (2/44), whilst, G. lamblia detected was detected in treated water samples from the Philippines (1/10) and in untreated water samples from Thailand (21/93), Malaysia (12/44), and the Philippines (17/23). Nitrate concentration was found to have a high positive correlation with (oo)cyst (0.993).

Conclusion

The presence of (oo)cysts in the water samples means that there is potential risk for zoonotic disease transmission in the studied countries. Detection using qPCR is feasible for quantifying both pathogenic C. parvum and G. lamblia in large water samples.

Comparison of propidium monoazide-quantitative PCR and reverse transcription quantitative PCR for viability detection of fresh Cryptosporidium oocysts following disinfection and after long-term storage in water samples

Purified oocysts of Cryptosporidium parvum were used to evaluate the applicability of two quantitative PCR (qPCR) viability detection methods in raw surface water and disinfection treated water. Propidium monoazide-qPCR targeting hsp70 gene was compared to reverse transcription (RT)-qPCR heat induced hsp70 mRNA in water samples spiked with oocysts. Changes in viability of flow cytometry sorted fresh and oocysts having undergone various aging periods (up to 48 months at 4 °C) were evaluated by Ct values obtained from the qPCR before and after disinfection scenarios involving ammonia or hydrogen peroxide. Both qPCR methods achieved stability in dose dependent responses by hydrogen peroxide treatment in distilled water that proved their suitability for the viability evaluations. Oocysts exposed to 3% hydrogen peroxide were inactivated at a rate of 0.26 h(-1) and 0.93 h(-1), as measured by the mRNA assay and the PMA-DNA assay, respectively. In contrast, the PMA-DNA assay was not as sensitive as the mRNA assay in detecting viability alterations followed by exposure to ammonia or after a long-term storage in 4 °C in distilled water since no dose response dependency was achieved. Surface water concentrates containing enhanced suspendable solids determined that changes in viability were frequently detected only by the mRNA method. Failure of, or inconsistency in the detection of oocysts viability with the PMA-DNA method, apparently resulted from solids that might have reduced light penetration through the samples, and thus inhibited the cross-linking step of PMA-DNA assay.

A rapid, sensitive, and cost-efficient assay to estimate viability of potato cyst nematodes

Potato cyst nematodes (PCNs) are quarantine organisms, and they belong to the economically most relevant pathogens of potato worldwide. Methodologies to assess the viability of their cysts, which can contain 200 to 500 eggs protected by the hardened cuticle of a dead female, are either time and labor intensive or lack robustness. We present a robust and cost-efficient viability assay based on loss of membrane integrity upon death. This assay uses trehalose, a disaccharide present at a high concentration in the perivitelline fluid of PCN eggs, as a viability marker. Although this assay can detect a single viable egg, the limit of detection for regular field samples was higher, ≈10 viable eggs, due to background signals produced by other soil components. On the basis of 30 nonviable PCN samples from The Netherlands, a threshold level was defined (ΔA(trehalose) = 0.0094) below which the presence of >10 viable eggs is highly unlikely (true for ≈99.7% of the observations). This assay can easily be combined with a subsequent DNA-based species determination. The presence of trehalose is a general phenomenon among cyst nematodes; therefore, this method can probably be used for (for example) soybean, sugar beet, and cereal cyst nematodes as well.

Detection of viable Cryptosporidium parvum in soil by reverse transcription-real-time PCR targeting hsp70 mRNA

Extraction of high-quality mRNA from Cryptosporidium parvum is a key step in PCR detection of viable oocysts in environmental samples. Current methods for monitoring oocysts are limited to water samples; therefore, the goal of this study was to develop a rapid and sensitive procedure for Cryptosporidium detection in soil samples. The efficiencies of five RNA extraction methods were compared (mRNA extraction with the Dynabeads mRNA Direct kit after chemical and physical sample treatments, and total RNA extraction methods using the FastRNA Pro Soil-Direct, PowerSoil Total RNA, E.Z.N.A. soil RNA, and Norgen soil RNA purification kits) for the direct detection of Cryptosporidium with oocyst-spiked sandy, loamy, and clay soils by using TaqMan reverse transcription-PCR. The study also evaluated the presence of inhibitors by synthesis and incorporation of an internal positive control (IPC) RNA into reverse transcription amplifications, used different facilitators (bovine serum albumin, yeast RNA, salmon DNA, skim milk powder, casein, polyvinylpyrrolidone, sodium hexametaphosphate, and Salmonella enterica serovar Typhi) to mitigate RNA binding on soil components, and applied various treatments (β-mercaptoethanol and bead beating) to inactivate RNase and ensure the complete lysis of oocysts. The results of spiking studies showed that Salmonella cells most efficiently relieved binding of RNA. With the inclusion of Salmonella during extraction, the most efficient mRNA method was Dynabeads, with a detection limit of 6 × 10(2) oocysts g(-1) of sandy soil. The most efficient total RNA method was PowerSoil, with detection limits of 1.5 × 10(2), 1.5 × 10(3), and 1.5 × 10(4) C. parvum oocysts g(-1) soil for sandy, loamy, and clay samples, respectively.

HBV vaccine efficacy and detection and genotyping of vaccineé asymptomatic breakthrough HBV infection in Egypt

AIM

To evaluate the impact of mass vaccination against the hepatitis B virus (HBV) in Egypt, and to search for vaccinee asymptomatic breakthrough HBV infection and its genotype.

METHODS

Seven hundred serum samples from vaccinated children and adults (aged 2-47 years) were used for quantitative and qualitative detection of HBsAb by ELISA. Three hundred and sixty serum samples representing undetectable or low or high HBsAb were screened for markers of active HBV infection (HBsAg, HBcAb (IgG) and HBeAb by ELISA, plus HBsAg by AxSYM) and HBV-DNA genotyping by nested multiplex PCR and by DNA sequencing.

RESULTS

It was found that 65% of children aged 2-4 years, and 20.5% aged 4-13 years, as well as 45% adults were good responders to HBV vaccination mounting protective level HBsAb. Poor responders were 28%, 59.5% and 34%, and non-responders were 7%, 20% and 21% respectively, in the three studied groups. Markers of asymptomatic HBV infections were HBsAg detected by ELISA in 2.5% vs 11.39% by AxSYM. Other markers were HBcAb (IgG) in 1.38%, HBeAb in 0.83%, and HBV-DNA in 7.8%. All had HBV genotype E infection.

CONCLUSION

It is concluded that HBV vaccine is efficient in controlling HBV infection among children and adults. The vaccine breakthrough infection was by HBV genotype E. A booster dose of vaccine is recommended, probably four years after initial vaccination.

A new duplex reverse transcription PCR for simultaneous detection of viable Cryptosporidium parvum oocysts and Giardia duodenalis cysts

OBJECTIVE

To simultaneously detect viable Cryptosporidium parvum oocysts and Giardia duodenalis cysts for the purpose of reducing time and cost spent.

METHODS

A duplex reverse transcription polymerase chain reaction (RT-PCR) method was newly developed.

RESULTS

Using duplex RT-PCR method for the hsp70 gene, viable (oo)cyst concentrations of 10(1) and 10(3) (oo)cysts/100 microL could be detected for C. parvum and G duodenalis, respectively. However, after heat-shock stimulation the expression of hsp70 mRNAs was detectable at 10(0) and 10(1) (oo)cysts/100 microL concentrations of C. parvum and G duodenalis, respectively. Thus, the detection sensitivity was significantly increased when the viable (oo)cysts were exposed to heat shock.

CONCLUSION

This study describes a new duplex RT-PCR method for hsp70 gene to detect the viable (oo)cysts of the C. parvum and G duodenalis with less time consumed and at a lower cost. This newly developed duplex RT-PCR method may be used to detect these parasites not only in aquatic environments but also in clinical samples.

Stress-induced Hsp70 gene expression and inactivation of Cryptosporidium parvum oocysts by chlorine-based oxidants

Our research on the mechanisms of action of chlorine-based oxidants on Cryptosporidium parvum oocysts in water revealed a dual-phase effect: (i) response to oxidative stress, which was demonstrated by induced expression of the Hsp70 heat shock gene, and (ii) oocyst inactivation as a result of long-term exposure to oxidants. The relative biocidal effects of sodium hypochlorite (bleach) and electrolytically generated mixed oxidant solution (MOS) on C. parvum oocysts were compared at identical free chlorine concentrations. Oocyst inactivation was determined by quantitative reverse transcription-PCR (qRT-PCR) amplification of the heat-induced Hsp70 mRNA and compared with tissue culture infectivity. According to both assays, within the range between 25 and 250 mg/liter free chlorine and with 4 h contact time, MOS exhibits a higher efficacy in oocyst inactivation than hypochlorite. Other RNA-based viability assays, aimed at monitoring the levels of beta-tubulin mRNA and 18S rRNA, showed relatively slow decay rates of these molecules following disinfection by chlorine-based oxidants, rendering these molecular diagnostic viability markers inappropriate for disinfection efficacy assessment.

Sensitivity of nested PCR in the detection of low numbers of Giardia lamblia cysts

Nested PCR was performed on individually isolated Giardia lamblia cysts in replicates of 50 for sets of 1, 2, 3, 4, 5, 7, and 10 cysts. Amplification ranged from 80% for 1 cyst to 100% for 10 cysts. The results suggest that nested PCR is well adapted for G. lamblia single-cyst detection.

Die-off of Cryptosporidium parvum in soil and wastewater effluents

AIMS

To determine the effect of biotic and abiotic components of soil on the viability and infectivity of Cryptosporidium parvum, and evaluate the suitability of viability tests as a surrogate for oocyst infectivity under various environmental settings.

METHODS AND RESULTS

The die-off of C. parvum in saturated and dry loamy soil was monitored over time by immunofluorescence assay (IFA) and PCR to estimate oocysts viability and by cell culture to estimate oocysts infectivity. Pseudomonas aeruginosa activity resulted in digestion of the outer layer of the oocysts, as demonstrated by loss of the ability to react in IFA. Whereas, P. aeruginosa activity did not affect the DNA amplification by PCR. A 1-log reduction in the oocysts infectivity was observed at 30 degrees C in distilled water and in saturated soil while oocysts viability was unchanged. Incubation for 10 days in dry loamy soil at 32 degrees C resulted in a 3-log(10) reduction in their infectivity while no change of oocysts viability was recorded.

CONCLUSIONS

Under low temperature, C. parvum oocysts may retain their infectivity for a long time. Soil desiccation and high temperatures enhance the die-off rate of C. parvum.

SIGNIFICANCE AND IMPACT OF THE STUDY

Previous die-off studies of C. parvum used viability tests that do not necessarily reflect the oocyst infectivity. Under low temperatures, there was an agreement observed between viability and infectivity tests and oocysts retained their infectivity for a long time. Desiccation and high temperatures enhance the loss of infectivity of C. parvum. The presented die-off data have significant implications on the management of wastewater reuse in warm environments.

Effectiveness of Cryptosporidium spp. oocysts detection and enumeration methods in water and milk samples

Cryptosporidium spp. oocyst recovery in water and milk samples was evaluated. Samples were inoculated with a suspension of 1.2×10(7) Cryptosporidium spp. oocysts and submitted to centrifugal flotation, using different solutions (sucrose, NaCl, MgSO4, ZnSO4, AlSO4, NH4SO4 40% and NH4SO4 80%). Centrifugation of the samples was carried out in two stages for concentration using two methods that differed in the order in which the saturated solutions were used, namely only in the first stage of method I and only in the second stage of method II. Oocyst identification was performed using the Kinyoun and Koster histochemical staining techniques. Samples analyzed by method I showed different degree of oocyst recovery, namely 10.9% with NaCl and 42.5% with MgSO4 in water and milk samples, while those samples analyzed by method II showed 10.6% with NaCl and 5.3% with sucrose in water and milk, respectively. Histochemical staining methods have no influence on the degree of oocysts recovery. The efficiency of Cryptosporidium spp. oocysts recovery methods depends on the nature and composition of the sample and on the methodology used for oocyst concentration.

Tools for investigating the environmental transmission of Cryptosporidium and Giardia infections in humans

Cryptosporidiosis and giardiasis are major public health concerns. The role of water and food in the epidemiology of these diseases is now well recognized. Molecular techniques are available to determine the species and genotypes of Cryptosporidium and Giardia and to distinguish human from non-human pathogens. Validated methods to determine the species, genotype and subgenotype that are present in heterologous mixtures should be applied to environmental samples to enable the monitoring and characterization of infection sources, disease tracking and the establishment of causative links to both waterborne and foodborne outbreaks. Meaningful interpretation of population structures and occurrence-prevalence baselines can be performed only by analysing a well-planned set of samples from all possible sources taken regularly over time, rather than focusing on outbreak investigations. For food, this includes such analyses in the country of origin.

Quantification and assessment of viability of Cryptococcus neoformans by LightCycler amplification of capsule gene mRNA

Cryptococcus neoformans is an opportunistic fungal pathogen. It infects the central nervous system causing meningitis, which is fatal if untreated, especially in AIDS and immunosuppressed patients. In this study a method of quantification and assessment of viability of C. neoformans by LightCycler RT-PCR amplification of the capsule gene mRNA is established. The sequence of primers and probes were derived from C. neoformans capsular CAP10 gene mRNA (GenBank accession number AF144574), and were species specific. Agarose gel electrophoresis analysis of LightCycler RT-PCR product showed a single band of 223 bp in length. In order to develop an internal control a 223 bp exon fragment of capsule mRNA was cloned in the pCR2.1 plasmid vector and RNA was generated by in vitro transcription. To determine the sensitivity of the assay, serial dilutions of in vitro-transcribed RNA with known concentrations and copy numbers, and serially diluted cultures of viable and nonviable C. neoformans were used. Under optimal conditions as little as 0.472 fg of capsule mRNA could be detected, corresponding to 1-10 c.f.u. ml(-1) of the sample. No amplification was observed from up to 10(5) heat/UV radiation-killed yeast cells and RNA of other bacterial and fungal pathogens and human genomic DNA or RNA. The amplification of capsule mRNA represents a sensitive, specific and quantitative means of detection of viable C. neoformans in clinical specimens and can be useful in the evaluation of the therapeutic efficacy of antifungal drugs in the treatment of C. neoformans meningitis.

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.

Cryptosporidium taxonomy: recent advances and implications for public health

There has been an explosion of descriptions of new species of Cryptosporidium during the last two decades. This has been accompanied by confusion regarding the criteria for species designation, largely because of the lack of distinct morphologic differences and strict host specificity among Cryptosporidium spp. A review of the biologic species concept, the International Code of Zoological Nomenclature (ICZN), and current practices for Cryptosporidium species designation calls for the establishment of guidelines for naming Cryptosporidium species. All reports of new Cryptosporidium species should include at least four basic components: oocyst morphology, natural host specificity, genetic characterizations, and compliance with the ICZN. Altogether, 13 Cryptosporidium spp. are currently recognized: C. muris, C. andersoni, C. parvum, C. hominis, C. wrairi, C. felis, and C. cannis in mammals; C. baïleyi, C. meleagridis, and C. galli in birds; C. serpentis and C. saurophilum in reptiles; and C. molnari in fish. With the establishment of a framework for naming Cryptosporidium species and the availability of new taxonomic tools, there should be less confusion associated with the taxonomy of the genus Cryptosporidium. The clarification of Cryptosporidium taxonomy is also useful for understanding the biology of Cryptosporidium spp., assessing the public health significance of Cryptosporidium spp. in animals and the environment, characterizing transmission dynamics, and tracking infection and contamination sources.

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.

Development of a PCR-enzyme immunoassay oligoprobe detection method for Toxoplasma gondii oocysts, incorporating PCR controls

Infections caused by Toxoplasma gondii are widely prevalent in animals and humans throughout the world. In the United States, an estimated 23% of adolescents and adults have laboratory evidence of T. gondii infection. T. gondii has been identified as a major opportunistic pathogen in immunocompromised individuals, in whom it can cause life-threatening disease. Water contaminated with feces from domestic cats or other felids may be an important source of human exposure to T. gondii oocysts. Because of the lack of information regarding the prevalence of T. gondii in surface waters, there is a clear need for a rapid, sensitive method to detect T. gondii from water. Currently available animal models and cell culture methods are time-consuming, expensive, and labor-intensive, requiring days or weeks for results to be obtained. Detection of T. gondii nucleic acid by PCR has become the preferred method. We have developed a PCR amplification and detection method for T. gondii oocyst nucleic acid that incorporates the use of hot-start amplification to reduce nonspecific primer annealing, uracil-N-glycosylase to prevent false-positive results due to carryover contamination, an internal standard control to identify false-negative results due to inadequate removal of sample inhibition, and PCR product oligoprobe confirmation using a nonradioactive DNA hybridization immunoassay. This method can provide positive, confirmed results in less than 1 day. Fewer than 50 oocysts can be detected following recovery of oocyst DNA. Development of a T. gondii oocyst PCR detection method will provide a useful technique to estimate the levels of T. gondii oocysts present in surface waters.

Recovery and detection of Cryptosporidium parvum oocysts from water samples using continuous flow centrifugation

Continuous flow centrifugation (CFC) was used in conjunction with immunomagnetic separation (IMS) and immunofluorescence microscopy (IFA) and nested PCR to recover and detect oocysts of Cryptosporidium parvum and cysts of Giardia intestinalis from 10L volumes of source water samples. Using a spiking dose of 100 oocysts, nine of 10 runs were positive by IFA, with a mean recovery of 4.4+/-2.27 oocysts; when another 10 runs were analyzed using nested PCR to the TRAP C-1 and Cp41 genes, nine of 10 were positive with both PCR assays. When the spiking dose was reduced to 10 oocysts in 10L, 10 of 12 runs were positive by IFA, with a mean oocyst recovery of 3.25+/-3.25 oocysts. When 10 cysts of Giardia intestinalis were co-spiked with oocysts into 10L of source water, five of seven runs were positive, with a mean cyst recovery of x=0.85+/-0.7. When 10 oocysts (enumerated using a fluorescence activated cell sorter) were spiked into 10L volumes of tap water, one of 10 runs was positive, with one oocyst detected. For the majority of the source water samples, turbidities of the source water samples ranged from 1.1 to 22 NTU, but exceeded 100 NTU for some samples collected when sediment was disturbed. The turbidities of pellets recovered using CFC and resuspended in 10 mL of water were very high (exceeding 500 NTU for the source water-derived pellets and 100 NTU for the tap water-derived pellets). While not as efficient as existing capsule-filtration based methods (i.e., US EPA methods 1622/1623), CFC and IMS may provide a more rapid and economical alternative for isolation of C. parvum oocysts from highly turbid water samples containing small quantities of oocysts.

An immunomagnetic separation-reverse transcription polymerase chain reaction (IMS-RT-PCR) test for sensitive and rapid detection of viable waterborne Cryptosporidium parvum

The public health problem posed by the waterborne parasite Cryptosporidium parvum incited the water supply industry to develop very accurate analytical tools able to assess the presence of viable oocysts in drinking water. In this study, we report the development of a viability assay for C. parvum oocysts based on immunomagnetic separation and reverse transcription polymerase chain reaction (IMS-RT-PCR). The detection limit of the IMS-RT-PCR assay, which targets the hsp70 heat shock-induced mRNA, was in the range of ten viable oocysts per 100-l tap water samples. Purified Cryptosporidium parvum oocysts were exposed to heating, freezing and three chemical disinfection treatments namely, chlorination, chlorine dioxide treatment and ozonation under conventional doses used in water treatment plants, then detected by IMS-PCR and IMS-RT-PCR. The results obtained by IMS-PCR showed that none of the treatments had an effect on oocyst detection. The inactivation of oocysts by boiling resulted in no RT-PCR signal. Chlorine as well as chlorine dioxide did not influence oocyst viability as determined by IMS-RT-PCR. Ozone more effectively inactivated oocysts. The IMS-RT-PCR assay in conjunction with IMS-PCR marks the development of a combined detection and viability test which can be used for drinking water quality control as well as for reliable evaluation of treatment efficiency.

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.

Cryptosporidium spp. no ambiente aquático: aspectos relevantes da disseminação e diagnóstico

A criptosporidiose é uma doença de importância para a saúde pública. A via de transmissão do Cryptosporidium parvum é associada freqüentemente à contaminação de água. Porém, estudos epidemiológicos revelam que sua incidência no ambiente aquático é subestimada. A falta de método apropriado de detecção para a pesquisa dos oocistos em amostras de água contribui para isso. O artigo discute vários aspectos do tema, dentre eles, a ocorrência desse patógeno no ambiente aquático e os avanços nos métodos de detecção. Apesar da existência de técnicas de biologia molecular para a identificação do agente, métodos parasitológicos ainda apresentam resultados satisfatórios. A reação em cadeia de polimerase (PCR) é um método de detecção promissor. A identificação dos oocistos de Cryptosporidium spp. na amostra de água é influenciada pelo número de oocistos presentes, pela sensibilidade do método e pelo método de concentração dos oocistos na amostra, cujo aperfeiçoamento é fundamental para a precisão da análise e pesquisa do parasito.

Concentration of Cryptosporidium, microsporidia and other water-borne pathogens by continuous separation channel centrifugation

AIMS

The aim of this study was to determine the effectiveness of continuous separation channel centrifugation for concentrating water-borne pathogens of various taxa and sizes.

METHODS AND RESULTS

Cryptosporidium parvum oocysts, Giardia lamblia cysts, Encephalitozoon intestinalis spores and Escherichia coli were seeded into different water matrices at densities ranging from 5 to 10 000 organisms l(-1) and recovered using continuous separation channel centrifugation. All pathogens were enumerated on membrane filters using microscopy. Recovery efficiencies were usually > 90%. Oocyst recovery did not vary with source water turbidity or with centrifuge flow rate up to 250 ml min(-1). Based on excystation, this concentration method did not alter oocyst viability.

CONCLUSIONS

Continuous separation channel centrifugation is an effective means of concentrating water-borne pathogens.

SIGNIFICANCE AND IMPACT OF THE STUDY

Methods are needed for detecting pathogens in drinking water to ensure public health. The first step for any pathogen detection procedure is concentration. However, this step has been problematic because recovery efficiencies of conventional methods, like filtration, are often low and variable, which may lead to false negatives. Continuous separation channel centrifugation can simultaneously concentrate multiple pathogens as small as 1 microm with high and reproducible efficiency in a variety of water matrices.

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.

U.S. drinking water challenges in the twenty-first century

The access of almost all 270 million U.S. residents to reliable, safe drinking water distinguishes the United States in the twentieth century from that of the nineteenth century. The United States is a relatively water-abundant country with moderate population growth; nonetheless, current trends are sufficient to strain water resources over time, especially on a regional basis. We have examined the areas of public water infrastructure, global climate effects, waterborne disease (including emerging and resurging pathogens), land use, groundwater, surface water, and the U.S. regulatory history and its horizon. These issues are integrally interrelated and cross all levels of public and private jurisdictions. We conclude that U.S. public drinking water supplies will face challenges in these areas in the next century and that solutions to at least some of them will require institutional changes.

Real-time PCR for the detection of Cryptosporidium parvum

Real time, TaqMan PCR assays were developed for the Cp11 and 18S rRNA genes of the protozoan parasite Cryptosporidium parvum. The TaqMan probes were specific for the genus Cryptosporidium, but could not hybridize exclusively with human-infectious C. parvum species and genotypes. In conjunction with development of the TaqMan assays, two commercial kits, the Mo Bio UltraClean Soil DNA kit, and the Qiagen QIAamp DNA Stool kit, were evaluated for DNA extraction from calf diarrhea and manure, and potassium dichromate and formalin preserved human feces. Real-time quantitation was achieved with the diarrhea samples, but nested PCR was necessary to detect C. parvum DNA in manure and human feces. Ileal tissues were obtained from calves at 3, 7, and 14 days post-infection, and DNA extracted and assayed. Nested PCR detected C. parvum DNA in the 7-day post-infection sample, but neither of the other time point samples were positive. These results indicate that real-time quantitation of C. parvum DNA, extracted using the commercial kits, is feasible on diarrheic feces, with large numbers of oocysts and small concentrations of PCR inhibitor(s). For samples with few oocysts and high concentrations of PCR inhibitor(s), such as manure, nested PCR is necessary for detection.

Occurrence and molecular genotyping of Cryptosporidium spp. in surface waters in Northern Ireland

AIMS

To investigate the incidence and genotype of Cryptosporidium parvum oocysts in drinking water sources in Northern Ireland for the period 1996-1999, and to compare conventional and molecular methods of detection.

METHODS AND RESULTS

Four hundred and seventy-four waters were investigated by conventional methods, namely immuno-fluorescent antibody detection (IFA; 380) and immuno-magnetic separation-IFA (IMS-IFA; 94), of which 14/474 (3%) were positive. Two hundred and fourteen samples (214/474) were also investigated by PCR techniques, targeting both the 18S rRNA and TRAP-C2 genes, of which 11/214 (5.1%) were positive. These 11 samples were classified as genotype II following sequence analysis of the TRAP-C2 amplicon.

CONCLUSIONS

This study demonstrated the low incidence of oocysts of C. parvum in water sources in Northern Ireland.

SIGNIFICANCE AND IMPACT OF THE STUDY

Such molecular-based techniques offer a number of advantages over conventional detection methodologies, namely greater sensitivity and specificity as well as the ability to provide accurate genotyping data rapidly, which may be valuable in directing operational management in potential outbreak situations.

Quantification of Candida albicans actin mRNA by the LightCycler system as a means of assessing viability in a model of cutaneous candidiasis

The LightCycler system (two-step reverse transcription-PCR-fluorescent hybridization [LC RT-PCR-FH]) was used to quantify Candida albicans actin mRNA as a means of assessing its viability in a reconstituted skin model of cutaneous candidiasis following the application of an antimycotic. A 192-bp ACT exon fragment was ligated into the pCR2.1 plasmid vector, and dilutions of the cloned insert (pACT; 4.092 kb) were used as the standard reference template. The LC RT-PCR-FH system could detect 1 fg of pACT, equivalent to 2.2 copies of the plasmid. The ACT exon-based PCR primers and FH probes were C. albicans specific, and electrophoretic analysis of the LC RT-PCR-FH assay product showed a 174-bp band in agarose gel. The number of copies of C. albicans ACT mRNA per milligram of tissue decreased with increasing amounts of amorolfine applied to a C. albicans-infected skin model, showing a reduction in viability. Detection and quantification of ACT mRNA in tissue by the LC RT-PCR-FH assay corresponded with cultural isolation of C. albicans from samples. The ACT mRNA-targeted LC RT-PCR-FH assay represents a sensitive, specific, rapid, and quantitative means of assessing the viability of C. albicans in infected tissue. This method may also be useful in evaluating the therapeutic efficacies of antifungal drugs in the treatment of various forms of candidiasis and other fungal diseases.

A randomized, blinded, controlled trial investigating the gastrointestinal health effects of drinking water quality

A double-blinded, randomized, controlled trial was carried out in in Melbourne, Australia, to determine the contribution of drinking water to gastroenteritis. Melbourne is one of the few major cities in the world that draws drinking water from a protected forest catchment with minimal water treatment (chlorination only). Six hundred families were randomly allocated to receive either real or sham water treatment units (WTUs) installed in their kitchen. Real units were designed to remove viruses, bacteria, and protozoa. Study participants completed a weekly health diary reporting gastrointestinal symptoms during the 68-week observation period. There were 2,669 cases of highly credible gastroenteritis (HCG) during the study (0.80 cases/person/year). The ratio of HCG episode rates for the real WTU group compared to the sham WTU group was 0.99 (95% confidence interval, 0.85-1.15, p = 0.85). We collected 795 fecal specimens from participants with gastroenteritis, and pathogens were not more significantly common in the sham WTU group. We found no evidence of waterborne disease in Melbourne. The application of this methodology to other water supplies will provide a better understanding of the relationship between human health and water quality.

Detection of Cryptosporidium parvum using oligonucleotide-tagged liposomes in a competitive assay format

To meet the technical challenge of accurately and rapidly detecting Cryptosporidium parvum oocysts in environmental water, the authors developed a single-use visual-strip assay. The first step in the overall assay procedure involves extracting C. parvum's mRNA coding for heat-shock protein hsp70, followed by amplification using nucleic acid sequence-based amplification (NASBA) methodology as described previously (Baeumner, A. J.; Humiston, M.; Montagna, R. A.; Durst, R. A. Anal. Chem., in press). Subsequently, generated amplicons are hybridized with dye-entrapping liposomes bearing DNA oligonucleotides (reporter probes) and biotin on their surface. The liposome-amplicon complex is then allowed to migrate upward on a nitrocellulose membrane strip. On the nitrocellulose strip, antisense-reporter probes are immobilized in a capture zone and antibiotin antibodies are immobilized in a second zone above the capture zone. Depending on the presence or absence of amplicon in the sample, the liposomes will bind to the capture zone, or they will be caught via their biotin tag in the second zone. Visual detection or gray-scale densitometry allows the quantification of liposomes that are present in either zone. The detection limit of the assay was determined to be 80 fmol amplicon/test. High accuracy and an internal assay control is established using this competitive format, because the presence or absence of liposomes can be quantified in the two capture zones.

Sensitive genotyping of Cryptosporidium parvum by PCR-RFLP analysis of the 70-kilodalton heat shock protein (HSP70) gene

A polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis of a 587-bp region of the Cryptosporidium parvum 70-kDa heat shock protein (HSP70) gene was developed for the detection and discrimination of the two major genotypes of C. parvum, genotype 1 and genotype 2. Ten Cryptosporidium isolates from non-immunocompromised people were identified as genotypes 1 and 2 (five each) by DNA sequencing of the 587-bp PCR product. This distinction was also achieved with the combination of two endonucleases, HinfI and ScaI, which generated a specific pattern for each genotype. A thorough screening of published sequences showed that this combination of enzymes could also be used for the discrimination of other species/genotypes of Cryptosporidium, especially Cryptosporidium meleagridis and the 'dog' genotype of C. parvum, both of which are infectious in humans. The PCR, conducted on genotypes 1 and 2 of C. parvum, could detect one oocyst per reaction. This new and sensitive genotyping procedure should be of particular interest when applied to the monitoring of water resources in which low concentrations of parasites usually occur.

Immunoassay for viable Cryptosporidium parvum oocysts in turbid environmental water samples

Cryptosporidium parvum oocysts in drinking water have been implicated in outbreaks of diarrheal disease. Current methods for monitoring environmental exposures to C. parvum only account for total number of oocysts without regard for the viability of the parasite. Measurement of oocyst viability, as indicated by an oocyst's ability to excyst, is useful because over time oocysts lose the ability to excyst and become noninfective. Thus, correlating the number of viable oocysts in drinking water with incidence and risk for disease should be more reliable than using the total number of oocysts. We have developed a quantitative assay capable of detecting low numbers of excystable, sporozoite-releasing C. parvum oocysts in turbid water samples. Monoclonal (CP7) and polyclonal antibodies have been developed against a sporozoite antigen released only during excystation or when the oocyst is mechanically disrupted. CP7 is specific for C. parvum and does not react with C. baileyi, C. muris, C. serpentis, Giardia spp., Eimeria spp., or E. nieschulzi. In this assay, oocysts in the test sample are first excysted and then centrifuged. The soluble sporozoite antigen is captured by CP7 attached to a magnetic bead. The captured antigen is then detected by ruthenium-labeled polyclonal antibodies via electrochemiluminescence. The CP7 viability assay can detect as few as 50 viable oocysts in a 1-ml assay sample with a turbidity as high as 200 Nephelometric turbidity units. This sensitive, turbidity-tolerant assay for oocyst viability may permit a better assessment of the disease risk associated with the presence of environmental oocysts.

Relevance of Cryptosporidium parvum hsp70 mRNA amplification as a tool to discriminate between viable and dead oocysts

Two mRNA extraction methods were compared in this study to clarify the discrepancies found between authors regarding the presence of mRNA in inactivated Cryptosporidium parvum oocysts. Cryptosporidium parvum heat shock protein 70 (hsp70) mRNA extraction was performed by using oligo(dT)20-labeled magnetic beads or by incubating oocyst lysates with DNase I. Significant differences in mRNA recovery rates between these 2 techniques were observed when working on inactivated oocysts. We consistently detected hsp70 mRNA in oocysts heated at 60 C for 30 min and oocysts incubated in 10% formalin for 2 hr when using DNase I in the mRNA extraction procedure. In contrast, no mRNA was detected in such oocysts when magnetic beads were used for the mRNA extraction. The selective capture of long poly-A tail mRNA, when using oligo(dT)20-labeled magnetic beads, is proposed in this paper for explaining the discrepancies observed between the two mRNA extraction methods compared in this study. DNA decay in inactivated and aging oocysts makes quantitative polymerase chain reaction a potential alternative technique for assessing C. parvum oocyst viability status in environmental samples.

Treatment of giardiasis

Giardia lamblia is both the most common intestinal parasite in the United States and a frequent cause of diarrheal illness throughout the world. In spite of its recognition as an important human pathogen, there have been relatively few agents used in therapy. This paper discusses each class of drugs used in treatment, along with their mechanism of action, in vitro and clinical efficacy, and side effects and contraindications. Recommendations are made for the preferred treatment in different clinical situations. The greatest clinical experience is with the nitroimidazole drugs, i.e., metronidazole, tinidazole, and ornidazole, which are highly effective. A 5- to 7-day course of metronidazole can be expected to cure over 90% of individuals, and a single dose of tinidazole or ornidazole will cure a similar number. Quinacrine, which is no longer produced in the United States, has excellent efficacy but may be poorly tolerated, especially in children. Furazolidone is an effective alternative but must be administered four times a day for 7 to 10 days. Paromomycin may be used during early pregnancy, because it is not systematically absorbed, but it is not always effective. Patients who have resistant infection can usually be cured by a prolonged course of treatment with a combination of a nitroimidazole with quinacrine.

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.

Identification of species and sources of Cryptosporidium oocysts in storm waters with a small-subunit rRNA-based diagnostic and genotyping tool

The identification of Cryptosporidium oocysts in environmental samples is largely made by the use of an immunofluorescent assay. In this study, we have used a small-subunit rRNA-based PCR-restriction fragment length polymorphism technique to identify species and sources of Cryptosporidium oocysts present in 29 storm water samples collected from a stream in New York. A total of 12 genotypes were found in 27 positive samples; for 4 the species and probable origins were identified by sequence analysis, whereas the rest represent new genotypes from wildlife. Thus, this technique provides an alternative method for the detection and differentiation of Cryptosporidium parasites in environmental samples.

Multiplex PCR: optimization and application in diagnostic virology

PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.

Gastritis and intestinal metaplasia in Syrian hamsters infected with Helicobacter aurati and two other microaerobes

Chronic gastritis and intestinal metaplasia associated with naturally occurring colonization by Helicobacter aurati and two other microaerobic species were observed in Syrian hamsters. Thirty-five hamsters, between 7 and 12 months of age, were evaluated from two research and three commercial facilities. Microaerobic bacteria were cultured from the hamster stomachs. These bacteria included H. aurati, a fusiform, urease-positive species; a second novel helical, urease-negative Helicobacter sp.; as well as a smaller, urease-negative Campylobacter sp. Southern blot analysis detected Helicobacter spp. DNA in the gastric tissues of all 35 hamsters; 15 hamsters also had Campylobacter sp. DNA in their gastric tissues. When examined by light microscopy, argyrophilic bacteria consistent with H. aurati or the second Helicobacter sp. were present in antral sections of 12 out of the 15 hamsters where bacteria were seen, while 9 out of the 15 hamsters had bacteria resembling the Campylobacter sp. The presence of Helicobacter spp. but not the presence of Campylobacter sp. was significantly correlated to gastritis severity (P < 0.0001 for Helicobacter spp., P = 0.6025 for Campylobacter sp.) and intestinal metaplasia, as measured by numbers of goblet cells (P = 0.0239 for Helicobacter spp., P = 0.5525 for Campylobacter sp.). Severely affected hamsters also had Giardia sp. within their metaplastic gastric pits. Hamsters with naturally occurring helicobacter-associated gastritis provide a model for studying the development of intestinal metaplasia and gastric giardiasis in H. pylori-infected humans.

Multiplex PCR: optimization and application in diagnostic virology

PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.

Identification of Mycobacterium ulcerans in the environment from regions in Southeast Australia in which it is endemic with sequence capture-PCR

We recently described the use of PCR to identify the environmental source of Mycobacterium ulcerans during an outbreak of ulcerative disease that occurred in a localized region of southeast Australia. The PCR used was based on amplification of the M. ulcerans-specific insertion sequence, IS2404. In this study we developed a new test that is a substantial improvement over the original PCR method in terms of sensitivity, reliability, and ease of use. In the new method magnetic bead sequence capture-PCR is used to detect two M. ulcerans sequences (IS2404 and IS2606) and total mycobacterial 16S ribosomal DNA. We used sequence capture-PCR to test water and plant material collected over a 12-month period during 1998 and 1999 from sites near the centers of two distinct foci of M. ulcerans infections. A golf course irrigation system in one area and a small shallow lake in another area repeatedly were PCR positive for M. ulcerans. Nearby sites and sites unrelated to the endemic areas were negative. Based on the PCR data, a most-probable-number method was used to estimate the concentration of M. ulcerans cells in positive samples from both regions. This procedure resulted in average concentrations of 0.5 cell per 100 ml of water and 40 cells per 100 g of detritus. Loss of the PCR signal coincided with a decrease in ulcerative disease in each area. These results provide further evidence that M. ulcerans may be transmitted from a point environmental source and demonstrate the utility of magnetic bead sequence capture-PCR for identification of nonculturable microbial pathogens in the environment.

An outbreak of cryptosporidiosis in an urban swimming pool: why are such outbreaks difficult to detect?

OBJECTIVE

To describe an outbreak of Cryptosporidium gastroenteritis in a swimming pool in Melbourne in early 1998 that was not detected through routine surveillance, and discuss difficulties in identifying such outbreaks.

METHODS

The Water Quality Study (WQS) was a large community-based study of gastroenteritis. Following suspicion of an outbreak of cryptosporidiosis within the study group, due to pool "X", a nested case control study was performed. Each case of Cryptosporidium gastroenteritis was matched with six controls and data from weekly Health Diaries from the WQS were reviewed. The Department of Human Services also instigated active surveillance among patrons at pool "X" using a systematic sample of 50 people from the pool's swim-school enrollment list.

RESULTS

There were seven cases of Cryptosporidium gastroenteritis in the case control study. Five cases and eight controls swam at pool "X" during the outbreak period. The adjusted odds of developing cryptosporidial diarrhoea if an individual swam at pool "X" was 34.5 (CI 2.3-2548). DHS identified another 11 laboratory confirmed cases associated with pool "X" as well as cases not linked to pool "X". 125 cases were identified throughout Melbourne with the suspected involvement of seven swimming pools.

CONCLUSIONS

Despite a high odds ratio of developing cryptosporidiosis this outbreak was not detected by routine surveillance methods. Current outbreak detection methods lack sensitivity, specificity or timeliness.

IMPLICATIONS

Improved surveillance systems are required if outbreaks of gastroenteritis are to be detected early so an intervention can be instigated to reduce the amount of subsequent illness.

Development and evaluation of a molecular viability assay for Pneumocystis carinii

Despite recent declines in incidence, Pneumocystis carinii pneumonia (PCP) remains the most commonly occurring opportunistic illness among persons with AIDS in the United States. While P. carinii DNA has been detected in patient respiratory specimens and in air samples collected from various indoor environments housing PCP patients, the viability of these organisms is unknown. For this reason, we have developed and evaluated a molecular viability assay for P. carinii. This method is based upon the detection of P. carinii mRNA by a reverse transcription-PCR that employs specific primers from a member of the heat shock protein 70 family. Under optimal assay conditions, these primers were capable of detecting as few as 100 viable trophozoites as determined by ethidium bromide staining, while no signal was obtained from 10(6) trophozoites killed by heat, desiccation, or UV radiation. This assay was also capable of distinguishing P. carinii from other common fungi present in the air. Therefore, this molecular viability assay may be useful in conjunction with standard bioaerosol collection devices and procedures for the detection of viable P. carinii collected from various indoor environments. It may also be useful in confirming the presence of viable trophozoites in respiratory specimens collected by noninvasive techniques from putatively infected individuals.

Cryptosporidiosis in birds--a review

The morphology, life cycle, maintenance, host specificity, incidence of Cryptosporidium species infecting birds, as well as the epidemiology, clinical signs, pathology, immunology, diagnosis, therapy, and control of avian cryptosporidiosis are reviewed. Based on the accepted criteria used for differentiation of Cryptosporidium isolates into valid species, this review places the validity of C. meleagridis in doubt and suggests that C. meleagridis isolated from birds is very closely related to, or identical with C. parvum infecting more than 100 species of mammals.