Real-time PCR assay for detection and genotype differentiation of Giardia lamblia in stool specimens

Prevalence of intestinal protozoan parasites among Asian schoolchildren: a systematic review and meta-analysis

PURPOSE

Intestinal protozoan parasites among Asian schoolchildren are a subject of concern due to their prevalence and potential health impact. Understanding and addressing this issue is crucial for public health in the region.

METHODS

We conducted a comprehensive search for articles published up to December 2023 across four databases, including Scopus, PubMed, ProQuest, and Web of Science. To estimate the combined prevalence, a random-effects model with a 95% confidence interval (CI) was applied, and the statistical analysis was performed using meta-analysis packages in R version (3.6.1). This study is registered with PROSPERO (CRD42023481146).

RESULTS

Among 131 eligible articles, the prevalence of intestinal protozoan parasites was 0.208 (95% CI = 0.180-0.238). Lebanon and Tajikistan had the highest country-level prevalence at 0.851 and 0.836, respectively, with Giardia duodenalis being the most prevalent species at 0.082.

CONCLUSION

In summary, our study highlights the urgent public health issue of protozoan parasites among Asian schoolchildren due to poor sanitation and water quality. Immediate interventions are essential, considering climate and socioeconomic factors, to combat these infections and improve overall health.

Systematic Review of Diagnostic Approaches for Human Giardiasis: Unveiling Optimal Strategies

Giardiasis, caused by the protozoan Giardia intestinalis, affects around 400 million people worldwide, emphasizing the critical need for accurate diagnosis to enhance human health, especially in children. Prolonged giardiasis in childhood can lead to intellectual deficits and other complications. A variety of diagnostic tools, including microscopic, immunological, and molecular methods, are available for detecting G. intestinalis infection. Choosing the most suitable method can be challenging due to the abundance of options. This systematic review assesses the reliability and applicability of these diagnostic modalities. Utilizing the Dimensions and Wordart platforms for data analysis, we focus on relevant literature addressing diagnostic methods for human giardiasis. Microscopic techniques, particularly Ritchie's method, emerge as the primary choice, followed by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). PCR's limited use is attributed to its high cost and infrastructure challenges in developing nations. In conclusion, our analysis supports microscopic methods as the gold standard for giardiasis diagnosis. However, in cases where symptoms persist despite a negative diagnosis, employing more sensitive diagnostic approaches is advisable.

Comparative study of a broad qPCR panel and centrifugal flotation for detection of gastrointestinal parasites in fecal samples from dogs and cats in the United States

BACKGROUND

For decades, zinc sulfate centrifugal fecal flotation microscopy (ZCF) has been the mainstay technique for gastrointestinal (GI) parasite screening at veterinary clinics and laboratories. Elsewhere, PCR has replaced microscopy because of generally increased sensitivity and detection capabilities; however, until recently it has been unavailable commercially. Therefore, the primary aim of this study was to compare the performance of real-time PCR (qPCR) and ZCF for fecal parasite screening. Secondary aims included further characterization of markers for hookworm treatment resistance and Giardia spp. assemblages with zoonotic potential and qPCR optimization.

METHODS

A convenience sampling of 931 canine/feline fecal samples submitted to a veterinary reference laboratory for routine ZCF from the Northeast US (11/2022) was subsequently evaluated by a broad qPCR panel following retention release. Detection frequency and agreement (kappa statistics) were evaluated between ZCF and qPCR for seven GI parasites [hookworm/(Ancylostoma spp.), roundworm/(Toxocara spp.), whipworm/(Trichuris spp.), Giardia duodenalis, Cystoisospora spp., Toxoplasma gondii, and Tritrichomonas blagburni] and detections per sample. Total detection frequencies were compared using a paired t-test; positive sample and co-infection frequencies were compared using Pearson's chi-squared test (p ≤ 0.05 significant) and qPCR frequency for hookworm benzimidazole (BZ) resistance (F167Y) and zoonotic Giardia spp. assemblage markers calculated. Confirmatory testing, characterization, and qPCR optimization were carried out with Sanger sequencing.

RESULTS

qPCR detected a significantly higher overall parasite frequency (n = 679) compared to ZCF (n = 437) [p =  < 0.0001, t = 14.38, degrees-of-freedom (df) = 930] and 2.6 × the co-infections [qPCR (n = 172) vs. ZCF (n = 66)], which was also significant (p =  < 0.0001, X2 = 279.49; df = 1). While overall agreement of parasite detection was substantial [kappa = 0.74; (0.69-0.78], ZCF-undetected parasites reduced agreement for individual and co-infected samples. qPCR detected markers for Ancylostoma caninum BZ resistance (n = 5, 16.1%) and Giardia with zoonotic potential (n = 22, 9.1%) as well as two parasites undetected by ZCF (T. gondii/T. blagburni). Sanger sequencing detected novel roundworm species, and qPCR optimization provided detection beyond ZCF.

CONCLUSIONS

These results demonstrate the statistically significant detection frequency advantage offered by qPCR compared to routine ZCF for both single and co-infections. While overall agreement was excellent, this rapid, commercially available qPCR panel offers benefits beyond ZCF with detection of markers for Giardia assemblages with zoonotic potential and hookworm (A. caninum) BZ resistance.

GIARDIA DUODENALIS GENOTYPING NOT LINKED TO CLINICAL SYMPTOMATOLOGY AND NUTRITIONAL STATUS OF SCHOOL-AGED CHILDREN OF SOLEDAD AND GALAPA MUNICIPALITY SCHOOLS, ATLÁNTICO, COLOMBIA

Giardia duodenalis genotypes A and B have been reported in Colombia. The population consisted of 235 schoolchildren whose ages ranged from 2 to 10 yr of age from the municipalities of Soledad and Galapa in the department of Atlántico, Colombia. Fecal samples were obtained and then analyzed in triplicate using the sedimentation in formalin-ether (Ritchie's method) and direct examination techniques. Of the 235 fecal samples, 35 samples were positive for G. duodenalis; positive samples were concentrated in a sucrose gradient and sonicated for 3 cycles of 20 sec. DNA extraction was performed, and the parasites were genotyped by conventional PCR amplifying a region of the β-giardin gene. A general prevalence of G. duodenalis of 13.2% was found, and of these genotyped samples, 13 (56.7%) and 7 (20%) corresponded to genotype A, 1 (4.3%), and 3 (25%) corresponded to genotype B, and 9 (39.1%) and 2 (16.7%) were not defined, in the municipalities Soledad and Galapa, respectively. Additionally, 23 children were diagnosed with symptomatologic giardiasis, and 12 were asymptomatic; the most relevant symptoms were abdominal pain (7, 20%) and diarrhea (13, 56.7%). The nutritional status of children with Giardia genotypes A and B were as follows: 3 in a state of malnutrition (10%), 10 normal (33.3%), and 6 overweight and obese (20%) with genotype A, and 1 in a state of malnutrition (3.3%) and 3 normal (10%) with genotype B. The genotypes found in G. duodenalis did not show an association with nutritional status or with the clinical manifestations evaluated in schoolchildren.

Comparison of gdh polymerase chain reaction-restriction fragment length polymorphism and tpi assemblage-specific primers for characterization of Giardia intestinalis in children

Background:

Aim and objectives:

Materials and Methods:

Results:

Conclusions:

Detection and identification of Giardia species using real-time PCR and sequencing

We report a specific region of Giardia spp. 18S ribosomal RNA (18S rDNA) that serves as an ideal target for quantitative PCR (qPCR) detection and sequencing to identify Giardia species, including the clinically-relevant G. duodenalis, in clinical and environmental samples. The presence of multiple copies of the 18S rDNA gene and variations in the selected 18S genomic region enabled the development of a rapid, sensitive qPCR screening method for the detection of Giardia spp. The analytical sensitivity of the Giardia qPCR assay was determined to be a cyst equivalent of 0.4 G. duodenalis cysts per PCR reaction. Amplicon sequencing of the PCR product confirmed Giardia spp. detection and among the 35 sequences obtained, 31, 3 and 1 isolates were classified as belonging to G. duodenalis, G. microti and G. muris, respectively. The TaqMan assay reported here may be useful for the detection of low levels of Giardia in clinical and environmental samples, and further enables the effective use of direct sequencing of the PCR product for Giardia confirmation and to identify major species of Giardia, including G. duodenalis.

Molecular detection of Tropheryma whipplei, Cryptosporidium spp., and Giardia lamblia among celiac disease samples

BACKGROUND

Celiac disease (CD) is one of the most common disorders, resulting from both environmental (gluten) and genetic factors. The clinical features of the Iranian CD are still unknown and there is insufficient information about the atypical presentation of CD from Iran. As, many previous reports revealed an association between controlled protozoal infections and the CD according to cytokines production, the aim of this study was to determine the prevalence of CD and possible co-infection with the most prevalent protozoal infections including Tropheryma whipplei, Cryptosporidium, and Giardia duodenalis among CD samples.

MATERIALS AND METHODS

In this study, from April 2014 to November 2016, 524 samples were obtained from small intestine of patients with gastrointestinal diseases referring to the Pathology Department of Namazi Hospital, Shiraz, Iran. Multiplex polymerase chain reaction assay was then performed on the histological positive CD samples for the prevalence of the microorganisms.

RESULTS

Sixty-four (12.21%) patients were diagnosed as having CD by histopathological examination. The prevalence of T. whipplei and Cryptosporidium spp. was 19 (29.69%) and 8 (12.5%) respectively, among CD positive samples there was no positive sample for Giardia lamblia.

CONCLUSION

The prevalence of CD among the southwestern Iranian population was high and comparable with other areas of Iran as well as many other countries. Furthermore, no significant association between the presence of T. whipplei, Cryptosporidium spp., and level of the histopathological changes of villi in the CD was observed (P > 0.05).

Giardiasis in symptomatic children from Sharkia, Egypt: genetic assemblages and associated risk factors

Giardia intestinalis (G. intestinalis) is a common enteric protozoan parasite worldwide and in Egypt. Identification of true prevailing Giardia assemblages helps in identification of the sources of infection. The study's aim was to determine the true prevalence of Giardia assemblages in Egyptian children from Sharkia governorate presenting with gastrointestinal symptoms and to investigate their association with molecularly detected Giardia. A total of 617 stool specimens were collected from children presenting with gastrointestinal symptoms in Alquraeen, Sharkia governorate, Egypt for 17 months. All stool specimens were microscopically examined by wet mount smear before and after stool concentration to recover parasitic stages. Giardia copro-DNA was amplified from microscopically detected stool specimens using Copro-nPCR targeting the tpi gene for Giardia, followed by sequencing products of nPCR. The molecular prevalence of Giardia among symptomatic children was 9.88%, 83% of which were assemblage B and 17% were assemblages A. Giardia affected both sexes and all ages and was most prevalent in preschool children. Abdominal pain was the most common GIT symptom followed by diarrhoea. However, none of the patients' demographic variables (sex, age, weight and height) nor clinical symptoms showed significant association with molecular detection of Giardia. Giardia was common among symptomatic children from Sharkia, Egypt, with the predominance of assemblage B, which suggests the possibility of sharing common transmission source and route. Giardia had age, sex and clinical symptom distributions without statistical significance. The results necessitate further genomic studies targeting multiple gene targets for a better understanding of the ecology, dynamics of transmission, pathogenicity and clinical impact of Giardia infection, to improve its management and strategic control.

Prevalence and genetic characterization of Giardia lamblia in relation to diarrhea in Limpopo and Gauteng provinces, South Africa

Background

Very few studies have determined the prevalence and assemblage distribution of Giardia lamblia in South Africa. The present study aimed to ascertain the prevalence of G. lamblia infection and the spread of the various assemblages in two communities in South Africa - Giyani, Limpopo province (rural community) and Pretoria Guateng province (urban community).

Methods

Prevalence was determined by immunological and molecular methods analyzing a total of 516 stool samples collected from patients visiting different health centres in Giyani and Pretoria. For immunological assays, samples were screened by ELISA to detect G. lamblia antigen. Furthermore, a semi nested PCR amplifying the triose phosphate isomerase (tpi) gene was used to differentiate between the two most common human assemblages (A and B).

Findings

Of the 516 participants, 40 (7.75%) were identified as positive by ELISA. A statistically significant correlation was observed between the stool texture and Giardia infection (ᵡ² = 10.533; p = .005). G. lamblia was significantly associated with watery stool types in females p = .008. Furthermore, a significant association was also noticed between the origin of samples (ᵡ² = 9.725; p = .002). No significant correlation between age and gender was noted. Regarding the age groups, most people who were infected were between 3 and 20 years. A statistically significant association was seen (p = .001) with the distribution of the pathogen with the stool type. The prevalence of Giardia infection was higher in watery stool samples (71.4%) in Giyani region (rural) whereas in Pretoria, high prevalence was found in loose stool samples (6.2%). Generally, the distribution was statistically significant in the stool type collected for the study (p = .005). Genotyping revealed more G. lamblia assemblage B (17.8%) than assemblage A (1.7%). Furthermore, 21.0% of the samples exhibited single infection while 4.2% had mixed infections. Assemblage B was more common in Giyani than in urban Pretoria.

Conclusions

The study confirms Giardia as an important cause of diarrhea in the concerned communities with people in rural areas more at risk compared to those in urban areas with higher prevalence among younger patients. Therefore, health education campaigns should target young age groups.

Large Scale Fabrication of Ordered Gold Nanoparticle-Epoxy Surface Nanocomposites and Their Application as Label-Free Plasmonic DNA Biosensors

A robust and scalable technology to fabricate ordered gold nanoparticle arrangements on epoxy substrates is presented. The nanoparticles are synthesized by solid-state dewetting on nanobowled aluminum templates, which are prepared by the selective chemical etching of porous anodic alumina (PAA) grown on an aluminum sheet with controlled anodic oxidation. This flexible fabrication technology provides proper control over the nanoparticle size, shape, and interparticle distance over a large surface area (several cm²), which enables the fine-tuning and optimization of their plasmonic absorption spectra for LSPR and SERS applications between 535 and 625 nm. The nanoparticles are transferred to the surface of epoxy substrates, which are subsequently selectively etched. The resulting nanomushrooms arrangements consist of ordered epoxy nanopillars with flat, disk-shaped nanoparticles on top, and their bulk refractive index sensitivity is between 83 and 108 nm RIU^-1. Label-free DNA detection is successfully demonstrated with the sensors by using a 20 base pair long specific DNA sequence from the parasite Giardia lamblia. A red-shift of 6.6 nm in the LSPR absorbance spectrum was detected after the 2 h hybridization with 1 μM target DNA, and the achievable LOD was around 5 nM. The reported plasmonic sensor is one of the first surface AuNP/polymer nanocomposites ever reported for the successful label-free detection of DNA.

Report of Giardia assemblages and giardiasis in residents of Guilan province-Iran

Giardia duodenalis is considered a highly diverse organism that infects a variety of mammalian hosts. Giardiasis is a significant public health problem in Iran. The purpose of this study was to investigate the occurrence of Giardia duodenalis (G. lamblia, G. intestinalis) infections in humans residing in the Guilan province of Iran. Stool samples were collected during 12 months from 8356 individuals that had been referred to certain hospitals in the capital city of Rasht in the Guilan province, of which 4126 were males and 4230 were females. The samples were separated into three groups according to patient age: group A 1-9 years old (n = 483); group B 10-19 years old (n = 491); and group C greater than 20 years old (n = 7382). The wet mount technique was performed directly on 8356 fecal samples for microscopy. Samples were examined using a saline and iodine direct smear technique in order to confirm the presence of G. duodenalis. The results indicated that 2.5% (206/8356) of the samples were identified as positive for G. duodenalis. A total of 30% of the infected patients (n = 62) had no symptoms. In symptomatic cases, the most common symptoms (46%, n = 95) were abdominal cramps and bloating. Twenty-four percent of patients (n = 50) had cramps, bloating, nausea, and diarrhea. Sixty positive samples were sent for G. duodenalis genotyping based on the amplification of the gdh gene. Forty-one PCR products were successfully selected and sequenced, where 38 (92.6%) samples were identified as genotype A/subgenotype II and in three samples (7.4%) genotype B/subgenotype IV. Genotype A-II had a dominant prevalence as compared to the genotype B-IV samples that were identified in the study. Based on the samples provided by the regional teaching hospitals and subsequent sample analysis, the authors concluded that assemblage A-II is most likely the most common Giardia subgroup infection in the Guilan region. Assemblages have been reported in both humans and animals; however, further studies need to investigate the role of domestic animals and water reservoirs as potential sources of Giardia infection in the Guilan region.

First report on Giardia duodenalis assemblage F in Slovakian children living in poor environmental conditions

BACKGROUND

Giardiasis is one of the most common gastrointestinal infections of humans and animals attributable to complex of eight morphologically identical genetic assemblages, further divided into sub-assemblages. Disease is common for a wide range of hosts and genetic characterization is needed for better understanding of multifaceted epidemiology for this protozoan parasite. The aim of this study was to identify genetic heterogeneity in assemblages and sub-assemblages of Giardiaduodenalis circulating among the children population living in deprived socioeconomic conditions.

METHODS

A total of 333 stool samples from children in eastern Slovakia were collected during the period of 2015-2016 and analysed by molecular methods. Molecular characterization of G. duodenalis was performed by sequence analysis of triose phosphate isomerase gene (tpi) and glutamate dehydrogenase gene (gdh).

RESULTS

G. duodenalis DNA was detected in 21 samples (6.3%), out of which 14 isolates (66.7%) belonged to assemblage B, 4 isolates (19.0%) to sub-assemblage AII and 3 isolates (14.3%) corresponded to assemblage F. As regards the determination of sub-assemblages of assemblage B, 4 isolates were characterized as sub-assemblage BIII and 6 isolates as sub-assemblage BIV.

CONCLUSION

This study is the first finding of cat specific assemblage F in man not only in Slovakia, but also in Europe. The absence of molecular data about G. duodenalis in companion animals in Slovakia establishes a strong need for further investigation for potential sources of giardiasis and understanding the epidemiology will help to improve the preventive strategies in eradication of infection in this population.

Advancements in Parasite Diagnosis and Challenges in the Management of Parasitic Infections: A Mini Review

Intestinal parasitic infections (IPIs) remain a widespread public health concern causing severe implications in both developed and developing countries. Globally, numerous studies have been carried out ranging from various communities to schoolchildren as well as indigenous communities. The infections are commonly caused by helminths (e.g. Ascaris lumbricoides, Trichuris trichiura and hookworm) and protozoa (e.g. Blastocystis hominis, Cryptosporidium sp., Entamoeba histolytica and Giardia duodenalis). Poor sanitation and poverty are some of the factors associated with IPIs. With the ever-increasing impact of IPIs, newer detection approaches have been developed and studied. The efficacy of diagnostic method is crucial to give an accurate identification of these parasites. Recent developments of diagnostic tools such as serology- and molecular-based assays are assisting the conventional method of microscopy in detecting and further confirming current or past infections and the specific species of parasites. Ongoing investigations in parasitic infections using these advanced tools will provide useful information that will enable the evaluation of the effectiveness of the current control program and thus, assist future planning for improved strategies in eradicating these parasitic infections.

Detection of Giardia intestinalis in water samples collected from natural water reservoirs and wells in northern and north-eastern Poland using LAMP, real-time PCR and nested PCR

Giardia intestinalis is a protozoan parasite, transmitted to humans and animals by the faecal-oral route, mainly through contaminated water and food. Knowledge about the distribution of this parasite in surface water in Poland is fragmentary and incomplete. Accordingly, 36 environmental water samples taken from surface water reservoirs and wells were collected in Pomerania and Warmia-Masuria provinces, Poland. The 50 L samples were filtered and subsequently analysed with three molecular detection methods: loop-mediated isothermal amplification (LAMP), real-time polymerase chain reaction (real-time PCR) and nested PCR. Of the samples examined, Giardia DNA was found in 15 (42%) samples with the use of LAMP; in 12 (33%) of these samples, Giardia DNA from this parasite was also detected using real-time PCR; and in 9 (25%) using nested PCR. Sequencing of selected positive samples confirmed that the PCR products were fragments of the Giardia intestinalis small subunit rRNA gene. Genotyping using multiplex real-time PCR indicated the presence of assemblages A and B, with the latter predominating. The results indicate that surface water in Poland, as well as water taken from surface wells, may be a source of Giardia strains which are potentially pathogenic for humans. It was also demonstrated that LAMP assay is more sensitive than the other two molecular assays.

The Use of Quinacrine in Nitroimidazole-resistant Giardia Duodenalis: An Old Drug for an Emerging Problem

Background

There is little evidence regarding the management of refractory giardiasis after treatment with nitroimidazoles. This study estimates the proportion of persistent giardiasis in 3 hospitals in Barcelona, describes associated risk factors and genotype, and evaluates the efficacy rate of quinacrine in those with persistent giardiasis.

Methods

A clinical, prospective, observational study was conducted in patients with giardiasis treated with nitroimidazoles. Those with persistent giardiasis were provided quinacrine. Molecular characterization of Giardia isolates was performed by polymerase chain reaction amplification of a fragment of tpi and bg genes.

Results

Seventy-seven patients were recruited and treated with nitroimidazoles, and in 14 of 71 (20%) of patients followed up, Giardia persisted. Refractory giardiasis was associated with malaise (P = .007) and anorexia (P = .02), with previous giardiasis (P = .03), and with previous antibiotic (P = .02) or antiparasitic(P = .04) use. Quinacrine had an effectiveness rate of 100% in refractory giardiasis (n = 13; 95% confidence interval = 75-100). Molecular characterization showed that 17 (25%) Giardia isolates belonged to assemblage A, and 31 (43%) belonged to assemblage B. In refractory giardiasis, assemblage A and B were found responsible in 4 and 6 cases, respectively.

Conclusions

Almost 20% of patients presented persistent giardiasis, belonging to both assemblages A and B, after nitroimidazole. Short course of quinacrine was effective in treating refractory cases. Further controlled studies should evaluate its efficacy and safety.

First detection and genotyping of Giardia intestinalis in stool samples collected from children in Ghazni Province, eastern Afghanistan and evaluation of the PCR assay in formalin-fixed specimens

It is estimated that faecal-orally transmitted diseases are common in Afghanistan, as a consequence of poor hygienic standards of life and widespread contamination of water and food with both human and animal faeces. However, there is little information in the literature concerning infections caused by intestinal parasites in the Afghan population. In this study, we report the occurrence of Giardia intestinalis assemblages (A and B) in formalin-fixed stool samples collected from 245 Afghan schoolchildren living in Ghazni Province in eastern Afghanistan. Detection of the parasite’s DNA and genotyping was performed using real-time PCR, specific to the β-giardin gene of G. intestinalis. Positive results were recorded in 52 (21.2%) samples. Genotyping was successful in 39 faecal samples and showed the predominance of assemblage B of G. intestinalis in this population (15 assemblage A and 24 assemblage B). Co-infection with both genotypes A and B was detected in four samples. Additionally, we evaluated the effect of 10% buffered formalin fixative on the detection of G. intestinalis DNA using real-time PCR and nested PCR characterised by different lengths of PCR products (74 and 479 bp, respectively). The human faeces containing the Giardia cysts were tested for 16 weeks. Amplification of G. intestinalis DNA with real-time PCR was possible up to 6 weeks of preservation of stool sample in formalin, compared to only 2 weeks with nested PCR. This suggests that real-time PCR is a more suitable tool in cases where stool samples have to be kept in formalin for longer periods of time.

Prevalence of Giardia duodenalis assemblages and sub-assemblages in symptomatic patients from Damascus city and its suburbs

Giardia duodenalis is one of the most important human enteric parasites worldwide and is endemic throughout the world with a vast range of mammalian hosts. However, there is limited information on the prevalent genetic variability of G. duodenalis in Syria. This study aimed to evaluate the predominance of G. duodenalis assemblages/sub-assemblages causing humans infection in the city of Damascus and its suburbs. 40 symptomatic giardiasis patients were recruited in this study. Fecal samples were genotyped using PCR/RFLP assay targeting the β-giardin and glutamate dehydrogenase (gdh) genes. HaeIII, BspL1 and RsaI restriction enzymes were used to differentiate between G. duodenalis assemblages/sub-assemblages. Our data showed that 65% of isolates were of assemblage A; 45% belonged to sub-assemblage AII and 20% to sub-assemblage AI. Assemblage B was detected in 27.5% of isolates; 12.5% fit in sub-assemblage BIV, 5% fit in sub-assemblage BIII and 10.5% fit in Discordant genotype BIII/BIV. Mixed genotypes (AII+BIII and AI+BIV) were identified in 3 isolates (7.5%). Significant correlation was found between Giardia AII sub-assemblage and weight loss symptom (P-value=0.05) as well as between contact with domestic animals (cats, P-value=0.027). Moreover, a significant correlation was found between sub-assemblage AI and livestock breeding (P-value=0.000). In conclusion genotyping of human Giardia duodenalis isolates suggests anthroponotic transmission for the route of infection in Damascus and its suburbs. Further studies are needed to screen a wide geographic areas in Syria and to estimate the prevalence of G. duodenalis infection in our population.

Comparison and evaluation of four methods for extracting DNA from Giardia duodenalis cysts for PCR targeting the tpi gene

Giardia duodenalis is an intestinal flagellated protozoan and the common cause of gastrointestinal diseases in human. This parasite can be seen in two different forms in its life cycle including as cyst and trophozoite. Due to presence of resistant cyst wall, DNA extraction inhibitors along with artifact in stool specimens, this study was performed aiming to evaluate four methods for DNA extraction from G. duodenalis cysts. Seventy G. duodenalis positive stool specimens that were confirmed by light microscope were included in this study. All stool samples were concentrated using four layered discontinuous sucrose flotation technique (0.5, 0.75, 1, and 1.5 M) and single-layered sucrose solution (0.85 M). The isolated cysts were then subjected to DNA extraction by four methods. To remove the artifacts, the extracted DNA were evaluated by PCR. The results of the present study showed the high level of optical density (OD) in the method I (P < 0.01) with the following steps; Giardia cysts plus crushed cover glass were vortexed. Then, the samples were boiled and then followed by freeze-thaw cycles, yet this method yielded the lowest concentration. Furthermore, the highest concentration were observed in the method II (P <0.01) with the following steps; Giardia cysts plus crushed cover glass and TAE buffer were mixed and then shaken, followed by boiling. Based on the results of the present study, using crushed cover glass, boiling and freeze-thaw cycles can be effective in destruction of G. duodenalis cyst wall and have enough efficiency for extracting DNA from G. duodenalis cysts.

Differentiation of entC1 from entC2/entC3 with a single primer pair using simple and rapid SYBR Green-based RT-PCR melt curve analysis

In spite of their involvement in foodborne illness, the epidemiological relevance of staphylococcal enterotoxin C (SEC) subtypes is poorly documented may be due to high sequence similarity. Among subtypes, SEC1, SEC2, and SEC3 exhibit more than 97 % homology because of which specific detection tools are seldom available to identify and differentiate them. In this study, a SYBR Green-based RT-PCR followed by melt curve analysis was developed for differentiation of entC1 from entC2/entC3 using a single primer pair. Nucleotide sequences of all three subtypes were analyzed using Clustal Omega program and the region with significant sequence variation/heterogeneity (where utmost SNPs were closely located and accessible for RT-PCR) was selected for amplification by designing a single primer pair that could amplify all three subtypes. In spite of same amplicon size, entC1 showed distinct melt peak at 76 °C. However, due to high similarity between entC2 and entC3, the developed format was deficient to discriminate between them and both showed melt peak at 82 °C. Reliability of developed RT-PCR was evaluated using various naturally contaminated samples and 91 food and clinical Staphylococcus aureus isolates where satisfactory results were obtained in comparison with commercial immunoassay kit and conventional PCRs using validated primers. To the best of our knowledge, this is the first method being reported to differentiate entC1 from entC2/entC3 using single primer pair which is unachievable by conventional PCR due to same amplicon size. As benefits, the method is sensitive, rapid, and inexpensive with no requirement of fluorescent probes, multiple primers, and post-PCR procedures. Thus, the assay might find its utility as a detection tool in epidemiological survey of foodborne outbreaks for simultaneous identification and differentiation of entC1 from entC2/entC3.

Giardia duodenalis in Damascus, Syria: Identification of Giardia genotypes in a sample of human fecal isolates using polymerase chain reaction and restriction fragment length polymorphism analyzing method

Giardia duodenalis is a common gastrointestinal parasite that infects humans and many other mammals. It is most prevalent in many developing and industrialized countries. G. duodenalis is considered to be a complex species. While no morphological distinction among different assemblages exist, it can be genetically differentiated into eight major assemblages: A to H. The aim of this study was to determine the genetic heterogeneity of G. duodenalis in human isolates (a study conducted for the first time in Syria). 40 fecal samples were collected from three different hospitals during the hot summer season of 2014. Extraction of genomic DNA from all Giardia positive samples (based on a microscopic examination) was performed using QIAamp DNA Stool Mini Kit. β-giardin gene was used to differentiate between different Giardia assemblages. The 514 bp fragment was amplified using the Polymerase Chain Reaction method, followed by digestion in HaeIII restriction enzyme. Our result showed that genotype A was more frequent than genotype B, 27/40 (67.5%); 4/40 (10%) respectively. A mixed genotype of A+B was only detected in 9 isolates (22.5%). This is the first molecular study performed on G. duodenalis isolates in Syria in order to discriminate among the different genotypes. Further expanded studies using more genes are needed to detect and identify the Giardia parasite at the level of assemblage and sub-assemblage.

Molecular characterization of Cryptosporidium and Giardia occurring in natural water bodies in Poland

Cryptosporidium and Giardia protozoa are zoonotic parasites that cause human gastroenteritis and can be transmitted to human through the fecal-oral route and water or food. Several species belong to these genera and their resistant forms occur in water, but only some of them are infectious to human. Health risk depends on the occurrence of infectious Cryptosporidium and Giardia species and genotypes in water, and only molecular techniques allow detecting them, as well as enable to identify the contamination source. In this work, genotyping and phylogenetic analysis have been performed on the basis of 18S rDNA and ß-giardin genes sequences of Cryptosporidium and Giardia, respectively, in order to provide the molecular characterization of these parasites detected earlier in five natural water bodies in Poland and to track possible sources of their (oo)cysts in water. Genotyping revealed a high similarity (over 99 up to 100 %) of analyzed sequences to cattle genotype of C. parvum isolated from cattle and human and to G. intestinalis assemblage B isolated from human. The sequences obtained by others originated from patients with clinical symptoms of cryptosporidiosis or giardiasis and/or with the infection confirmed by different methods. The contamination of three examined lakes is probably human-originated, while the sources of contamination of two remaining lakes are wild and domestic animals. Obtained phylogenetic trees support suggestions of other authors that the bovine genotype of C. parvum should be a separate species, as well as A and B assemblages of G. intestinalis.

Management of chronic Giardia infection

Advances in our understanding of chronic giardiasis (CG) may improve our care of patients in this stage of the disease. This review proposes a new concept of CG and highlights the recent advances in our understanding and management of this condition. According to this review, management requires, initially, an accurate diagnosis, which may exclude several conditions that can mimic CG. Optimal treatment requires a tailored approach which includes the recognition of the known modifiable causes of this health condition, assessment of symptoms and potential complications, their treatment utilizing, if necessary, a multidisciplinary team, and an ongoing monitoring for the effect of therapy - weighing the efficacy of individual drugs - all of these together may lead to a successful treatment of CG.

The anti-giardial effectiveness of fungal and commercial chitosan against Giardia intestinalis cysts in vitro

Chitosan with poly-N-acetylglucosamine sequences is a deacetylated derivative of chitin that can be found in the exoskeletons of crabs, shrimp and lobsters, the cuticles of insects and the cell walls of fungi. The aim of the present study was to compare the effects of fungal chitosan (FC) prepared from the cell walls of Penicillium viridicatum and Penicillium aurantiogriseum with commercially available chitosan (CC) against Giardia intestinalis cysts in vitro. The giardia cysts were isolated using a sucrose method. Four concentrations (50, 100, 200 and 400 μg/ml) of each type of prepared chitosan were applied for 10, 30, 60 and 180 min. The viability of the cysts was checked via 0.1 % eosin staining. Our results indicate that P. viridicatum (with a 47.5 % DD) and P. aurantiogriseum (with a 47.3 % DD) at different concentrations after 180 min precipitated, respectively, 56, 69, 81 and 100 %, and 63, 75, 86 and 100 % mortality rates. CC (with a 54 % DD) showed 79, 84, 93 and 100 % mortality rates. In conclusion, both FC and CC at 400 μg/ml concentrations after 180 min of exposure showed the most potent effect against G. intestinalis cysts. Accordingly, chitosan could be suggested as a new natural nanoform agent for future research in the safe and effective treatment of Giardia infections.

Giardia duodenalis typing from stools: a comparison of three approaches to extracting DNA, and validation of a probe-based real-time PCR typing assay

A weighted, multi-attribute approach was used to compare three methods for direct extraction of Giardia duodenalis DNA from 15 microscopy-positive stools: (1) a QIAamp spin-column method for stools including a 10 min incubation at 95 °C, (2) method 1 preceded by five freeze–thaw cycles and (3) bead beating with guanidine thiocyanate using a FastPrep-28 machine followed by liquid-phase silica purification of DNA. The attributes compared included DNA yield measured using a new triose phosphate isomerase (tpi) gene probe-based real-time PCR, also described here. All three methods shared 100 % PCR positivity, while the bead-beating method provided the highest G. duodenalis DNA yield (P<0.01). However, when other weighted attributes, including biocontainment, resources and technical requirements, were also considered, spin-column extraction with prior freeze–thaw treatment (method 2) was deemed the most desirable and was selected for use. The tpi real-time PCR typing assay was designed to discriminate between the main human infectious assemblages of G. duodenalis (A and B) and was evaluated initially using standard isolates. Validation using microscopy-positive stools from 78 clinical giardiasis cases revealed 100 % typability; 20 (26 %) samples contained assemblage A, 56 (72 %) assemblage B and two (3 %) assemblages A and B. While the epidemiological significance of assemblage distribution will be revealed as more isolates are typed and analysed with patient demographic and exposure data, the utility of this assay and its ready application in our laboratory workflow and result turnaround margins is already evident.

Simplified protocol for DNA extraction and amplification of 2 molecular markers to detect and type Giardia duodenalis

We evaluated the ability of 3 kits: QIAmp® DNA stool mini kit (Qiagen, Hilden, Germany), PureLink PCR Purification®, and PureLink™ Genomic DNA® (Invitrogen, Carlsbad, CA, USA) for DNA extraction, and of 2 molecular markers (heat shock protein [HSP] and β-giardin genes) for detection and genotyping of Giardia duodenalis stool samples. The detection and typing limits of the markers were determined by the DNA concentration of trophozoites and cysts and were tested in 26 clinical samples. Of the 3 kits tested, the PureLink PCR Purification gave the best results when tested with clinical samples with low, intermediate, and high numbers of cysts. The DNA extracted from trophozoites and cysts was diluted successively in 1:2 ratios until it was no longer possible to observe the amplified product in polyacrylamide gel. Similarly, a suspension of cysts was diluted until no cysts were observed, and then the DNA was extracted. The amount of DNA of trophozoites and cysts for the typing of the parasite was smaller for the HSP marker than for β-giardin. Combined use of both markers allowed us to detect DNA of Giardia in parasitologically positive samples in a higher percentage (75%) than the results obtained for each marker and in 1 parasitologically negative sample, indicating that this combination increased the potential to accurately detect and genotype this parasite. We also concluded that the HSP marker has a higher limit of detection and typing than the β-giardin marker and that the DNA extraction method tested for G. duodenalis is simpler and more efficient than those that are currently in use and can be applied on a large scale.

Discharge-based QMRA for estimation of public health risks from exposure to stormwater-borne pathogens in recreational waters in the United States

This study is the first to report a quantitative microbial risk assessment (QMRA) on pathogens detected in stormwater discharges-of-concern, rather than relying on pathogen measurements in receiving waters. The pathogen concentrations include seven "Reference Pathogens" identified by the U.S. EPA: Cryptosporidium, Giardia, Salmonella, Norovirus, Rotavirus, Enterovirus, and Adenovirus. Data were collected from 12 sites representative of seven discharge types (including residential, commercial/industrial runoff, agricultural runoff, combined sewer overflows, and forested land), mainly during wet weather conditions during which times human health risks can be substantially elevated. The risks calculated herein therefore generally apply to short-term conditions (during and just after rainfall events) and so the results can be used by water managers to potentially inform the public, even for waters that comply with current criteria (based as they are on a 30-day mean risk). Using an example waterbody and mixed source, pathogen concentrations were used in QMRA models to generate risk profiles for primary and secondary water contact (or inhalation) by adults and children. A number of critical assumptions and considerations around the QMRA analysis are highlighted, particularly the harmonization of the pathogen concentrations measured in discharges during this project with those measured (using different methods) during the published dose-response clinical trials. Norovirus was the most dominant predicted health risk, though further research on its dose-response for illness (cf. infection) is needed. Even if the example mixed-source concentrations of pathogens had been reduced 30 times (by inactivation and mixing), the predicted swimming-associated illness rates - largely driven by Norovirus infections - can still be appreciable. Rotavirus generally induced the second-highest incidence of risk among the tested pathogens while risks for the other Reference Pathogens (Giardia, Cryptosporidium, Adenovirus, Enterovirus and Salmonella) were considerably lower. Secondary contact or inhalation resulted in considerable reductions in risk compared to primary contact. Measurements of Norovirus and careful incorporation of its concentrations into risk models (harmonization) should be a critical consideration for future QMRA efforts. The discharge-based QMRA approach presented herein is particularly relevant to cases where pathogens cannot be reliably detected in receiving waters with detection limits relevant to human health effects.

Barcoding of Giardia duodenalis isolates and derived lines from an established cryobank by a mutation scanning-based approach

We barcoded 25 in vitro isolates (representing 92 samples) of Giardia duodenalis from humans and other animals, which have been assembled by the Upcroft team at the Queensland Institute of Medical Research over a period of almost three decades. We used mutation scanning-coupled sequencing of loci in the triosephosphate isomerase, glutamate dehydrogenase and β-giardin genes, combined with phylogenetic analysis, to genetically characterise them. Specifically, the isolates (n514) of G. duodenalis from humans from Australia (AD113; BRIS/83/HEPU/106; BRIS/87/HEPU/713; BRIS/89/HEPU/1003; BRIS/92/HEPU/1541; BRIS/92/HEPU/1590; BRIS/92/HEPU/2443; BRIS/93/HEPU/1706), Malaysia (KL/92/IMR/1106) and Afghanistan (WB), a cat from Australia (BAC2), a sheep from Canada (OAS1) and a sulphur-crested cockatoo from Australia (BRIS/95/HEPU/2041) represented assemblage A (sub-assemblage AI-1, AI-2 or AII-2); isolates (n510) from humans from Australia (BRIS/91/HEPU/1279; BRIS/92/HEPU/2342; BRIS/92/HEPU/2348; BRIS/93/HEPU/1638; BRIS/93/HEPU/1653; BRIS/93/HEPU/1705; BRIS/93/HEPU/1718; BRIS/93/HEPU/1727), Papua New Guinea (BRIS/92/HEPU/1487) and Canada (H7) represented assemblage B (sub-assemblage BIV) and an isolate from cattle from Australia (BRIS/92/HEPU/1709) had a match to assemblage E. Isolate BRIS/90/HEPU/1229 from a human from Australia was shown to represent a mixed population of assemblages A and B. These barcoded isolates (including stocks and derived lines) now allow direct comparisons of experimental data among laboratories and represent a massive resource for transcriptomic, proteomic, metabolic and functional genomic studies using advanced molecular technologies.

The effect of multiple primer-template mismatches on quantitative PCR accuracy and development of a multi-primer set assay for accurate quantification of pcrA gene sequence variants

Quantitative PCR (qPCR) is a critical tool for quantifying the abundance of specific organisms and the level or expression of target genes in medically and environmentally relevant systems. However, often the power of this tool has been limited because primer-template mismatches, due to sequence variations of targeted genes, can lead to inaccuracies in measured gene quantities, detection failures, and spurious conclusions. Currently available primer design guidelines for qPCR were developed for pure culture applications, and available primer design strategies for mixed cultures were developed for detection rather than accurate quantification. Furthermore, past studies examining the impact of mismatches have focused only on single mismatches while instances of multiple mismatches are common. There are currently no appropriate solutions to overcome the challenges posed by sequence variations. Here, we report results that provide a comprehensive, quantitative understanding of the impact of multiple primer-template mismatches on qPCR accuracy and demonstrate a multi-primer set approach to accurately quantify a model gene pcrA (encoding perchlorate reductase) that has substantial sequence variation. Results showed that for multiple mismatches (up to 3 mismatches) in primer regions where mismatches were previously considered tolerable (middle and 5' end), quantification accuracies could be as low as ~0.1%. Furthermore, tests were run using a published pcrA primer set with mixtures of genomic DNA from strains known to harbor the target gene, and for some mixtures quantification accuracy was as low as ~0.8% or was non-detect. To overcome these limitations, a multiple primer set assay including minimal degeneracies was developed for pcrA genes. This assay resulted in nearly 100% accurate detection for all mixed microbial communities tested. The multi-primer set approach demonstrated herein can be broadly applied to other genes with known sequences.

Investigation of Possible Correlation between Giardia duodenalis Genotypes and Clinical Symptoms in Southwest of Iran

BACKGROUND

Giardia duodenalis is one of the most important human enteric parasites throughout the world. Clinical symptoms of this parasite vary from asymptomatic infection to chronic diarrhea. Still it is not clear, whether different types of pathogenesis are due to different strains of organism or to variable host factors. The purpose of this study was to investigate possible correlation of clinical symptoms with assemblages among symptomatic and asymptomatic cases collected from southwest of Iran.

METHODS

Fecal samples were collected from 100 symptomatic and asymptomatic cases, which were positive for G. duodenalis. The samples were subjected to semi-nested PCR and RFLP for gdh gene.

RESULTS

Among symptomatic patients, 54% had mixed genotypes AII and BIII, 28% and 18% of samples indicated assemblages BIII and AII, respectively. In contrast, among asymptomatic cases, 64%, 26% and 10%samples had mixed genotypes, BIII and AII assemblages, respectively. Statistical analysis using Chi- Square test showed that there was no significant correlation between assemblage and clinical symptoms in current study.

CONCLUSION

High prevalence of mixed infection in both groups may affect this conclusion, therefore further study in more details are necessary to clarify these finding. Additionally, it is important to carry out investigations regarding human host factors as well.

Evaluation of the zoonotic potential of Giardia duodenalis in fecal samples from dogs and cats in Ontario

This study determined the distribution and zoonotic potential of Giardia duodenalis assemblage types among canine and feline fecal samples from Ontario. The effectiveness of Giardia assemblage typing methods by sequencing the genes of small subunit ribosomal RNA (ssu-rRNA), β-giardin (bg), glutamate dehydrogenase (gdh), and triose phosphate isomerase (tpi) was evaluated simultaneously. From 2008 to 2010, 118 canine and 15 feline Giardia positive fecal samples were tested. The ssu-rRNA sequencing method typed 64% (75/118) and 87% (13/15) of the Giardia-positive canine and feline samples, respectively. Among the typeable samples, 68% (51/75) of canine samples contained G. duodenalis assemblage D and 31% (23/75) contained G. duodenalis assemblage C (both non-zoonotic assemblage types). Only 1% (1/75) of the typeable canine samples contained a potentially zoonotic assemblage B. In contrast, 100% (13/13) of the typeable feline samples contained potentially zoonotic assemblages A (n = 12) or B (n = 1).

Development and evaluation of a real-time PCR assay for quantification of Giardia and Cryptosporidium in sewage samples

Cryptosporidium and Giardia are major causes of diarrheal disease in humans worldwide and are major causes of protozoan waterborne diseases. Two DNA TaqMan PCR-based Giardia and Cryptosporidium methods targeting a 74-bp sequence of the β-giardin Giardia gene and a 151-bp sequence of the COWP Cryptosporidium gene, respectively, were used as models to compare two different LNA/DNA TaqMan probes to improve the detection limit in a real-time PCR assay. The LNA probes were the most sensitive resulting in 0.96 to 1.57 lower C t values than a DNA Giardia TaqMan probe and 0.56 to 2.21 lower than a DNA Cryptosporidium TaqMan probe. Evaluation of TaqMan Giardia and Cryptosporidium probes with LNA substitutions resulted in real-time PCR curves with an earlier C t values than conventional DNA TaqMan probes. In conclusion, the LNA probes could be useful for more sensitive detection limits.

Zoonotic potential and molecular epidemiology of Giardia species and giardiasis

Molecular diagnostic tools have been used recently in assessing the taxonomy, zoonotic potential, and transmission of Giardia species and giardiasis in humans and animals. The results of these studies have firmly established giardiasis as a zoonotic disease, although host adaptation at the genotype and subtype levels has reduced the likelihood of zoonotic transmission. These studies have also identified variations in the distribution of Giardia duodenalis genotypes among geographic areas and between domestic and wild ruminants and differences in clinical manifestations and outbreak potentials of assemblages A and B. Nevertheless, our efforts in characterizing the molecular epidemiology of giardiasis and the roles of various animals in the transmission of human giardiasis are compromised by the lack of case-control and longitudinal cohort studies and the sampling and testing of humans and animals living in the same community, the frequent occurrence of infections with mixed genotypes and subtypes, and the apparent heterozygosity at some genetic loci for some G. duodenalis genotypes. With the increased usage of multilocus genotyping tools, the development of next-generation subtyping tools, the integration of molecular analysis in epidemiological studies, and an improved understanding of the population genetics of G. duodenalis in humans and animals, we should soon have a better appreciation of the molecular epidemiology of giardiasis, the disease burden of zoonotic transmission, the taxonomy status and virulences of various G. duodenalis genotypes, and the ecology of environmental contamination.

Detection and species identification of microsporidial infections using SYBR Green real-time PCR

Diagnosis of microsporidial infections is routinely performed by light microscopy, with unequivocal non-molecular species identification achievable only through electron microscopy. This study describes a single SYBR Green real-time PCR assay for the simultaneous detection and species identification of such infections. This assay was highly sensitive, routinely detecting infections containing 400 parasites (g stool sample)(-1), whilst species identification was achieved by differential melt curves on a Corbett Life Science Rotor-Gene 3000. A modification of the QIAamp DNA tissue extraction protocol allowed the semi-automated extraction of DNA from stools for the routine diagnosis of microsporidial infection by real-time PCR. Of 168 stool samples routinely analysed for microsporidian spores, only five were positive by microscopy. By comparison, 17 were positive for microsporidial DNA by real-time analysis, comprising 14 Enterocytozoon bieneusi, one Encephalitozoon cuniculi and two separate Pleistophora species infections.

Evaluation of multiplex tandem real-time PCR for detection of Cryptosporidium spp., Dientamoeba fragilis, Entamoeba histolytica, and Giardia intestinalis in clinical stool samples

The aim of this study was to describe the first development and evaluation of a multiplex tandem PCR (MT-PCR) assay for the detection and identification of 4 common pathogenic protozoan parasites, Cryptosporidium spp., Dientamoeba fragilis, Entamoeba histolytica, and Giardia intestinalis, from human clinical samples. A total of 472 fecal samples submitted to the Department of Microbiology at St. Vincent's Hospital were included in the study. The MT-PCR assay was compared to four real-time PCR (RT-PCR) assays and microscopy by a traditional modified iron hematoxylin stain. The MT-PCR detected 28 G. intestinalis, 26 D. fragilis, 11 E. histolytica, and 9 Cryptosporidium sp. isolates. Detection and identification of the fecal protozoa by MT-PCR demonstrated 100% correlation with the RT-PCR results, and compared to RT-PCR, MT-PCR exhibited 100% sensitivity and specificity, while traditional microscopy of stained fixed fecal smears exhibited sensitivities and specificities of 56% and 100% for Cryptosporidium spp., 38% and 99% for D. fragilis, 47% and 97% for E. histolytica, and 50% and 100% for G. intestinalis. No cross-reactivity was detected in 100 stool samples containing various other bacterial, viral, and protozoan species. The MT-PCR assay was able to provide rapid, sensitive, and specific simultaneous detection and identification of the four most important diarrhea-causing protozoan parasites that infect humans. This study also highlights the lack of sensitivity demonstrated by microscopy, and thus, molecular methods such as MT-PCR must be considered the diagnostic methods of choice for enteric protozoan parasites.

Real-time PCR/RFLP assay to detect Giardia intestinalis genotypes in human isolates with diarrhea in Egypt

Two major genotypic assemblages of Giardia intestinalis infect humans; the nested real-time polymerase chain reaction (PCR) was used for targeting the triose phosphate isomerase (tpi) gene to detect and genotype G. intestinalis in human feces in Egypt. Among 97 fecal samples, 30 (31%) were diagnosed as giardiasis by saline wet mount microscopy after staining with Lugol's iodine. The tpi gene was amplified from 41 (42.3%) fecal samples, of which 11 were microscopy-negative specimens. Of the total samples, 24 (58.5%) contained assemblage A group I, and 7 (17.1%) were assemblage A group II from the group of patients complaining of intermittent diarrhea. Eight (19.5%) samples contained assemblage B from patients with persistent diarrhea. Two (5%) samples had a mixture of assemblage A group II and assemblage B. The technique was able to detect as few as 20 trophozoites per PCR on fecal DNA-isolated, microscopy-negative, and quantitative (q)PCR-positive specimens; there was a higher average cycle threshold value than microscopy-positive and qPCR-positive specimens, suggesting that they represented true, low-burden infections. In conclusion, we could genotype G. intestinalis from fresh stool samples in Egypt; in infections commonly presented with intermittent diarrhea, the most prevalent genotype was assemblage A group I. The most vulnerable age group included 10- to 20-yr-old individuals.

Clinical significance of enteric protozoa in the immunosuppressed human population

Globally, the number of immunosuppressed people increases each year, with the human immunodeficiency virus (HIV) pandemic continuing to spread unabated in many parts of the world. Immunosuppression may also occur in malnourished persons, patients undergoing chemotherapy for malignancy, and those receiving immunosuppressive therapy. Components of the immune system can be functionally or genetically abnormal as a result of acquired (e.g., caused by HIV infection, lymphoma, or high-dose steroids or other immunosuppressive medications) or congenital illnesses, with more than 120 congenital immunodeficiencies described to date that either affect humoral immunity or compromise T-cell function. All individuals affected by immunosuppression are at risk of infection by opportunistic parasites (such as the microsporidia) as well as those more commonly associated with gastrointestinal disease (such as Giardia). The outcome of infection by enteric protozoan parasites is dependent on absolute CD4(+) cell counts, with lower counts being associated with more severe disease, more atypical disease, and a greater risk of disseminated disease. This review summarizes our current state of knowledge on the significance of enteric parasitic protozoa as a cause of disease in immunosuppressed persons and also provides guidance on recent advances in diagnosis and therapy for the control of these important parasites.

LNA probes in a real-time TaqMan PCR assay for genotyping of Giardia duodenalis in wastewaters

AIMS

This study describes an approach for genotyping Giardia cysts obtained from wastewater treatment plants (WTPs) in Spain using real-time PCR (qPCR) in combination with immunomagnetic beads.

METHODS AND RESULTS

A 50-cycle amplification of a 74-bp fragment of the Giardia beta-giardin gene was adopted from a previous qPCR method. Additionally, two locked nucleic acid (LNA) probes were designed (LNA P434 P1 for assemblage A and LNA P434 H3 for assemblage B). All 16 wastewater samples analysed were positive with the immunofluorescence assay (IFA). Assemblage A was detected in all WTP samples using primer-LNA probe P434 P1 set. Giardia duodenalis identification was confirmed by PCR-RFLP analysis and sequencing of the beta-giardin gene in the water samples found positive by IFA and qPCR. Among the 16 assemblage A isolates that were sequenced, two subtypes were identified; 11 corresponded to the A2 subgenotype, whereas three corresponded to the subgenotype A3. A mixture of subgenotypes was found in the remaining two isolates.

CONCLUSIONS

The newly developed qPCR assays were able to discern G. duodenalis assemblages A and B in wastewater.

SIGNIFICANCE AND IMPACT OF THE STUDY

The real-time PCR assays provided a rapid method for detection and one-step genotyping of G. duodenalis from wastewater samples, and its application would contribute to understanding the distribution and abundance of G. duodenalis assemblages A and B in wastewater.

Sexual transmission of intestinal parasites in men who have sex with men

Direct oral-anal sexual contact is a common practice among men who have sex with men (MSM) and is implicated in the transmission of various enteric pathogens including intestinal parasites. The present study reviewed data on the sexual transmission of intestinal parasites among MSM, and highlighted advances in the diagnosis of such infections. The emergence and spread of intestinal parasites is of public health concern particularly in the homosexual community. Intestinal parasitic infection should be considered in the differential diagnosis of gastrointestinal disease in this population. Combination of traditional diagnostic procedures with implementation of testing based on novel molecular methods in the accurate identification of intestinal parasites is important so that early intervention and control of infection is facilitated.

Development of a direct DNA extraction protocol for real-time PCR detection of Giardia lamblia from surface water

Giardia lamblia is one of the most recognized waterborne protozoan parasites causing gastrointestinal disease. A simple but effective DNA extraction protocol for real-time PCR detection from surface water samples was developed in this study. Eleven protocols were compared, which consisted of freeze-thaw treatments (liquid N(2) and boiling water) and purification using the Qiagen DNeasy kit, together with different combinations of proteinase K, PVP360, GITC and Chelex 100 incubation. Using concentrated surface water samples spiked with G. lamblia cysts, the necessary steps for high DNA recovery were shown to be freeze-thaw, DNeasy purification and Chelex 100 incubation. Multiple rounds of freeze-thaw treatment (five cycles per round) were reported for the first time in this study to significantly increase the DNA yield from G. lamblia cysts, from ~20% after one round of freeze-thaw to 40 and 70% after two and three-rounds of freeze-thaw, respectively. More than three rounds of freeze-thaw treatment did not promote additional DNA recovery. The final protocol included three-three-rounds of freeze-thaw treatment, DNeasy purification and Chelex 100 incubation. This method was simpler, more cost-effective, and had a comparable DNA recovery to methods involving immunomagnetic separation.

Transmission cycles of Giardia duodenalis in dogs and humans in Temple communities in Bangkok--a critical evaluation of its prevalence using three diagnostic tests in the field in the absence of a gold standard

The prevalence and associated risk factors for Giardia duodenalis in canine and human populations in Temple communities of Bangkok, Thailand were determined by evaluating three common diagnostic methods utilised to detect Giardia, namely zinc sulphate flotation and microscopy, an immunofluoresence antibody test and nested polymerase chain reaction (PCR) based on the SSU-rDNA gene. The diagnostic sensitivity and specificity together with the negative and positive predictive values of each test were evaluated in the absence of a gold standard using a Bayesian approach. The median estimates of the prevalence of infection with G. duodenalis in dogs and humans in Thailand were 56.8% (95% PCI, 30.4%, 77.7%) and 20.3% (95% PCI, 7.3%, 46.3%) respectively. PCR and immunofluorescence antibody tests (IFAT) were the most accurate tests overall with diagnostic sensitivity and specificity of 97.4% (95% PCI, 88.5%, 99.9%) and 56.2% (95% PCI, 40.4%, 82.9%) for the PCR and 61.8% (95% PCI, 40.8%, 99.1%) and 94.7% (95% PCI, 87.4%, 99.1%) for IFAT respectively Three cycles, anthroponotic, zoonotic and dog-specific cycles of G. duodenalis were shown to be operating among the human and canine populations in these Temple communities in Bangkok, supporting the role of the dog as a potential reservoir for Giardia infections in humans.

Multiple-subgenotype infections of Giardia intestinalis detected in Palestinian clinical cases using a subcloning approach

To evaluate the geographic distribution of Giardia intestinalis genotypes in Nablus, West Bank, Palestine, a genotyping study was performed using clinical fecal samples. Microscopic examination confirmed that 8 of 69 (11.6%) samples were G. intestinalis positive, and subsequent genotyping analyses targeting the small-subunit ribosomal RNA (18S rRNA) and glutamate dehydrogenase (GDH) genes revealed the G. intestinalis genotypes within the 8 samples. Of these 8 samples, 6 were clustered with assemblage A-II and the remaining 2 samples were clustered with assemblage B by 18S rRNA gene analysis; however, direct sequencing of the GDH gene segments from the latter 2 samples showed a mixed infection profile. To assess those samples, we employed a subcloning approach and successfully isolated 6 independent assemblage B subgenotypes. These partial GDH gene sequences (393 bp) had 15 single-nucleotide polymorphisms, all of which were synonymous transition substitutions at the third nucleotide position of codons. From the results, we concluded that the highly polymorphic gene loci such as GDH gene locus might provide us an opportunity to obtain a detailed molecular data even from the samples with multiple-subgenotype mixed infections. Therefore, subcloning approach is recommended in genotyping studies, especially in those conducted in giardiasis-endemic areas, where the repeated and cumulative infections could be commonly expected.