A nested, multiplex, PCR assay for the simultaneous detection and differentiation of Entamoeba histolytica and Entamoeba dispar in faeces

Symptomatic and Asymptomatic Protist Infections in Hospital Inpatients in Southwestern China

Cryptosporidium spp., Entamoeba histolytica, Giardia duodenalis, and Blastocystis sp. infections have been frequently reported as etiological agents for gastroenteritis, but also as common gut inhabitants in apparently healthy individuals. Between July 2016 and March 2017, stool samples (n = 507) were collected from randomly selected individuals (male/female ratio: 1.1, age range: 38–63 years) from two sentinel hospitals in Tengchong City Yunnan Province, China. Molecular (PCR and Sanger sequencing) methods were used to detect and genotype the investigated protist species. Carriage/infection rates were: Blastocystis sp. 9.5% (95% CI: 7.1–12.4%), G. duodenalis 2.2% (95% CI: 1.1–3.8%); and E. histolytica 2.0% (95% CI: 0.9–3.6%). Cryptosporidium spp. was not detected at all. Overall, 12.4% (95% CI: 9.7–15.6) of the participants harbored at least one enteric protist species. The most common coinfection was E. histolytica and Blastocystis sp. (1.0%; 95% CI: 0.3–2.2). Sequence analyses revealed that 90.9% (10/11) of the genotyped G. duodenalis isolates corresponded to the sub-assemblage AI. The remaining sequence (9.1%, 1/11) was identified as sub-assemblage BIV. Five different Blastocystis subtypes, including ST3 (43.7%, 21/48), ST1 (27.1%, 13/48), ST7 (18.8%, 9/48), ST4 (8.3%, 4/48), and ST2 (2.1%, 1/48) were identified. Statistical analyses confirmed that (i) the co-occurrence of protist infections was purely random, (ii) no associations were observed among the four protist species found, and (iii) neither their presence, individually or jointly, nor the patient’s age was predictors for developing clinical symptoms associated with these infections. Overall, these protist mono- or coinfections are asymptomatic and do not follow any pattern.

Occurrence and genetic identifications of porcine Entamoeba, E. suis and E. polecki, at Tangerang in West Java, Indonesia

Entamoeba suis and E. polecki subtype (ST) 1 and ST3 recently have been inferred to be virulent in pigs. However, because relevant molecular epidemiological surveys have been limited, the prevalences of these species remain unknown and their pathogenicities are still controversial. We surveyed 196 fecal samples of pigs (118 of adults, 78 of piglets) at Tangerang in West Java, Indonesia, in 2017, employing PCR using porcine Entamoeba-specific primers. E. suis was the more frequently detected species, observed in 81.1% of samples, while E. polecki ST1 and ST3 were detected in 18.4% and 17.3% of samples, respectively; mixed infections (harboring 2-3 species or subtypes of Entamoeba) were confirmed in 29.3% of positive samples. Statistically significant differences in the positive rates were not seen between adult pigs and piglets, except for those of E. polecki ST3. The prevalences of Eimeria spp. and/or Cystoisospora suis (79.1%), strongyles (55.6%), and Strongyloides spp. (6.1%) were also observed morphologically in the samples. Further chronological or seasonal investigations of pigs and humans in these high-prevalence areas are needed to assess the virulence of the Entamoeba parasites, including the effects on pig productivity, and to evaluate the zoonotic impacts of these organisms.

Pathogenic Entamoeba histolytica, but not Entamoeba dispar, induce neutrophil extracellular trap (NET) formation

Amoebiasis is an infection of global importance, caused by the eukaryotic parasite Entamoeba histolytica. Pathogenic E. histolytica is associated worldwide with over a million cases of amoebic dysentery, colitis, and amoebic liver abscess. In contrast, the nonpathogenic Entamoeba dispar does not cause these diseases, although it is commonly found in the same areas as pathogenic amoeba. Entamoeba histolytica infection is usually associated with infiltrating neutrophils. These neutrophils appear to play a defensive role against this parasite, by mechanisms not completely understood. Recently, our group reported that neutrophil extracellular traps (NET) are produced in response to E. histolytica trophozoites. But, there is no information on whether nonpathogenic E. dispar can also induce NET formation. In this report, we explored the possibility that E. dispar leads to NET formation. Neutrophils were stimulated by E. histolytica trophozoites or by E. dispar trophozoites, and NET formation was assessed by video microscopy. NET induced by E. histolytica were important for trapping and killing amoebas. In contrast, E. dispar did not induce NET formation in any condition. Also E. dispar did not induce neutrophil degranulation or reactive oxygen species production. In addition, E. histolytica-induced NET formation required alive amoebas and it was inhibited by galactose, N-acetylgalactosamine, and lactose. These data show that only alive pathogenic E. histolytica activates neutrophils to produce NET, and suggest that recognition of the parasite involves a carbohydrate with an axial HO- group at carbon 4 of a hexose.

Development of molecular diagnostic protocols for detecting three types of Entamoeba from diarrheal and asymptomatic pigs and environmental moist soils

Entamoeba suis and Entamoeba polecki subtypes (ST) 1 and 3 have recently been implicated in disease outbreaks in pigs. However, the distributions of these parasites in Japan and the potential sources of infection on farms still remain unclear. Here, we examined a farm of fattening/growing pigs with abnormal feces in Kagoshima Prefecture, Japan, and found the presence of parasites in the farm environment. Examination of intestinal tissues from pigs presenting with ulcerative colitis revealed a large number of trophozoites that had invaded the lesions. We identified single and mixed infections of E. suis and E. polecki ST1 and ST3 in paraffin sections or fecal samples from affected pigs. Two subtypes of Entamoeba were identified using four primer sets by PCR and sequencing. The parasites were detected in moist soil samples obtained around the drinking water source or puddles, implicating transmission of cysts via contaminated soils. Additionally, we found evidence of Entamoeba spp. and coinfections in surveyed pigs without any diarrhea at two neighboring farms. Our results establish methods for successfully identification of parasites, including cases in which multiple infections are present.

First molecular identification of Entamoeba polecki in a piglet in Japan and implications for aggravation of ileitis by coinfection with Lawsonia intracellularis

Parasitic Entamoeba spp. are found in many vertebrate species including humans, as well as many livestock including pigs. In pigs, three Entamoeba spp., E. suis, and E. polecki and E. histolytica as zoonotic species, have been identified, but their pathogenicity has not been fully characterized. Here, we report the bacteriological, virological, and histopathological examination of three piglets with chronic diarrhea. Two animals appeared to be additionally infected with Lawsonia intracellularis, which caused a characteristic proliferative ileitis. In the piglet infected with Entamoeba spp., the trophozoites (approximately 10-15 μm with one nucleus in their cytoplasm) invaded into the lamina propria and the disease was worsened by the formation of ulcers and pseudomembranes. Genetic analysis identified the parasite as E. polecki (99.5% identity). Although E. polecki in humans or animals might be less pathogenic in the case of a single infection, coinfections with other pathogens including L. intracellularis may increase the severity of the disease.

Intestinal amebae

Among the Entamoeba species that infect humans, Entamoeba histolytica causes diseases, Entamoeba dispar is a harmless commensal, Entamoeba moshkovskii seems to be a pathogen, and the pathogenicity of Entamoeba bangladeshi remains to be investigated. Species-specific detection needed for treatment decisions and for understanding the epidemiology and pathogenicity of these amebae. Antigen-based detection methods are needed for E dispar, E moshkovskii, and E bangladeshi; and molecular diagnostic test capable of detecting E histolytica, E dispar, E moshkovskii, and E bangladeshi simultaneously in clinical samples. Next-generation sequencing of DNA from stool is needed to identify novel species of Entamoeba.

Genetic analysis of Enterobius vermicularis isolated from a chimpanzee with lethal hemorrhagic colitis and pathology of the associated lesions

Human pinworms, Enterobius vermicularis, are normally recognized as minor pathogens. However, a fatal case of human pinworm infection has been reported in a nonhuman primate, a zoo reared chimpanzee. Here, we histopathologically examined the lesions in tissues from the deceased chimpanzee and genetically characterized the isolated worms to investigate the pathogenicity and determine the phylogeny. We identified ulcers deep in the submucosa where many parasites were found to have invaded the lamina propria mucosa or submucous tissue. An inflammatory reaction consisting mainly of neutrophils and lymphocytes but not eosinophils was observed around the parasites, and intense hemorrhage in the lamina propria was confirmed. The parasites were morphologically similar to E. vermicularis based on the shape of the copulatory spicules. Mitochondrial cytochrome c oxidase subunit 1 gene products were amplified from worm DNA by PCR and were genetically identified as E. vermicularis based on >98.7% similarity of partial sequences. Phylogenetic analysis revealed that the sequences clustered together with other chimpanzee E. vermicularis isolates in a group which has been referred to as type C and which differs from human isolates (type A). The samples were negative for bacterial pathogens and Entamoeba histolytica indicating that E. vermicularis could be pathogenic in chimpanzees. Phylogenetic clustering of the isolates indicated that the parasite may be host specific.

Molecular diagnosis of infectious diarrhea: focus on enteric protozoa

Robust detection of enteric protozoa is a critical step toward determining the etiology of diarrhea. Widespread use of conventional microscopy, culturing and antigen detection in both industrial and developing countries is limited by relatively low sensitivity and specificity. Refinements of these conventional approaches that reduce turnaround time and instrumentation have yielded strong alternatives for clinical and research use. However, advances in molecular diagnostics for protozoal, bacterial, viral and helminth infections offer significant advantages in studies seeking to understand pathogenesis, transmission and long-term consequences of infectious diarrhea. Quantitation of enteropathogen burden and highly multiplexed platforms for molecular detection dramatically improve predictive power in emerging models of diarrheal etiology, while eliminating the expense of multiple tests.

Ultrastructural characteristics and molecular identification of Entamoeba suis isolated from pigs with hemorrhagic colitis: implications for pathogenicity

Protozoan parasites of the genus Entamoeba infect many classes of vertebrates and are primarily classified based on morphological criteria. To date, only a few species have been proven to cause disease. Here, we examined the pathology of infected pigs with hemorrhage and detected Entamoeba parasites. Isolates were characterized genetically and ultrastructurally to identify the species. Histopathologically, bleeding and thrombus formation were seen only in the large intestine mucosa, where a large number of trophozoites or some Entamoeba cysts were observed around breakdowns in the lamina propria. No screw-shaped bacteria were detected in the lesions, and no pathogenic bacteria such as Brachyspira spp. were detected in fecal cultures. Interestingly, electron microscopy revealed that the parasites possessed mitochondrial organelles, unlike other Entamoeba spp. The isolates were identified as Entamoeba suis by PCR analysis and sequencing of the small subunit ribosomal RNA (SSU rRNA) gene. In phylogenetic analyses based on the actin gene, the E. suis isolate formed a cluster with Entamoeba histolytica and Entamoeba invadens, as well as with other parasites of the Amoebidae. Whether the pathogenicity of the E. suis isolate is affected by the severity of infection or host health status remains unclear; however, our results suggest that E. suis could cause or exacerbate clinical symptoms such as hemorrhagic colitis or diarrhea.

LUMINEX®: a new technology for the simultaneous identification of five Entamoeba spp. commonly found in human stools

Background

Six species of the genus Entamoeba, i.e., E. histolytica, E. dispar, E. moshkovskii, E. polecki, E. coli, and E. hartmanii can be found in human stools. Among these, only E. histolytica is considered to be pathogenic, causing intestinal and extra-intestinal disease, but it is morphologically identical to E. dispar and E. moshkovskii. In general, E. polecki, E. coli, and E. hartmanii can be differentiated morphologically from E. histolytica, but some of their diagnostic morphologic features may overlap creating issues for the differential diagnosis. Moreover, the previous inability to differentiate among Entamoeba species has limited epidemiologic information on E histolytica. The objective of this study was to develop a rapid, high-throughput screening method using Luminex technique for the simultaneous detection and differentiation of Entamoeba species.

Methods

PCR amplification was performed with biotinylated Entamoeba sp 18S rRNA gene primers, designed to amplify a fragment ranging from 382 to 429 bp of the Entamoeba spp studied. Regions of this fragment that could differentiate among E. histolytica, E. moshkovskii, E. dispar, E. hartmanii and E. coli were selected to design hybridization probes to link to Luminex beads. The assay was standardized with cloned DNA samples of each species and evaluated with 24 DNA extracts from samples obtained from individuals diagnosed with these amebas in their stools.

Results

Using this approach we were able to correctly identify E. histoltyica, E. dispar, E hartmanni, E. coli and E. moshkovskii in all specimens studied. From twenty four samples tested by microscopy, PCR/DNA Sequencing and real-time PCR, 100% agreed with PCR-Luminex assay for identification of E. dispar, E. moshkovskii, E. hartmanni, E. histolytica, and E. coli.

Conclusion

These results show that this method could be used in the diagnostic detection of Entamoeba spp in fecal samples. This diagnostic test was useful to clearly distinguish E histolytica from other species and also to strengthen epidemiologic data on Entamoeba spp.

Evaluation of an immunochromatographic dip strip test for simultaneous detection of Cryptosporidium spp, Giardia duodenalis, and Entamoeba histolytica antigens in human faecal samples

Immunochromatographic (IC) tests may play an important role in the future diagnosis of parasitic diseases because of their speed and simplicity of use. A recently developed test to detect Cryptosporidium spp, Giardia duodenalis and Entamoeba histolytica was evaluated. Microscopy and PCR were the "gold standard" reference techniques and the results of this IC test were compared with those obtained with ELISA and IC single test for the three parasites. One hundred sixty stool samples were assayed. Using microscopy, 22 samples were diagnosed as positive for Cryptosporidium spp., 31 for Giardia duodenalis, 41 for Entamoeba histolytica/dispar, and 68 had a negative diagnosis for the three parasites. Results of IC tests show sensitivities of 70-72% for Cryptosporidium, 90-97% for Giardia and 62.5% for Entamoeba histolytica. Specificities were of 93.6-94.9%, >99% and 96.1%, respectively. In all diagnoses, agreement with microscopy and PCR was over 90%, except in the triple test and microscopy in E. histolytica detection that was 76.3%, due to the inability of microscopy to differentiate E. histolytica from nonpathogenic species such as E. dispar or E. moshkovskii. The triple stool immunoassays provide adequate sensitivities and specificities for use in outbreak situations, for screening proposals and for massive assays in endemic areas where a large number of samples must be analysed or as complementary test for individual diagnosis.

Development of multiplex real-time polymerase chain reaction for detection of Entamoeba histolytica, Entamoeba dispar, and Entamoeba moshkovskii in clinical specimens

Multiplex real-time polymerase chain reaction (PCR) was developed for differential detection of Entamoeba histolytica, Entamoeba dispar, and Entamoeba moshkovskii. Specific primers were designed for all three species, and then differentiation of E. histolytica and E. dispar was achieved simultaneously using a hybridization probe and melting curve analysis, whereas E. moshkovskii was detected with a separate probe under the same condition. This assay detected as little as 0.2 pg of E. histolytica DNA and 2 pg each for E. dispar and E. moshkovskii DNA. Thirty-five clinical samples suspected to be E. histolytica infection by microscopy were tested. The results showed 32 positive samples; four samples were E. histolytica and 28 samples were E. dispar. Interestingly, one E. dispar positive sample showed a mixed infection with E. moshkovskii. This is the first report of E. moshkovskii infection from Thailand and this assay is currently the most rapid and sensitive method to differentiate these human amoebas.

Differential identification of Entamoeba spp. based on the analysis of 18S rRNA

Entamoeba histolytica is known to cause intestinal and extra-intestinal disease while the other Entamoeba species are not considered to be pathogenic. However, all Entamoeba spp. should be reported when identified in clinical samples. Entamoeba polecki, Entamoeba coli, and Entamoeba hartmanii can be differentiated morphologically from E. histolytica, but some of their diagnostic morphologic features overlap. E. histolytica, Entamoeba dispar, and Entamoeba moshkovskii are morphologically identical but can be differentiated using molecular tools. We developed a polymerase chain reaction (PCR) procedure followed by DNA sequencing of specific regions of 18S rRNA gene to differentiate the Entamoeba spp. commonly found in human stools. This approach was used to analyze 45 samples from cases evaluated for the presence of Entamoeba spp. by microscopy and a real-time PCR method capable of differential detection of E. histolytica and E. dispar. Our results demonstrated an agreement of approximately 98% (45/44) between the real-time PCR for E. histolytica and E. dispar and the 18S rRNA analysis described here. Five previously negative samples by microscopy revealed the presence of E. dispar, E. hartmanii, or E. coli DNA. In addition, we were able to detect E. hartmanii in a stool sample that had been previously reported as negative for Entamoeba spp. by microscopy. Further microscopic evaluation of this sample revealed the presence of E. hartmanii cysts, which went undetected during the first microscopic evaluation. This PCR followed by DNA sequencing will be useful to refine the diagnostic detection of Entamoeba spp. in stool and other clinical specimens.

Presence and diagnosis of amebic infestation in Turkish patients with active ulcerative colitis

BACKGROUND

It is difficult to definitively diagnose acute amebiasis, particularly when this condition is superimposed on inflammatory bowel disease. Our goals in this study were to determine the prevalence of amebiasis in individuals with active ulcerative colitis, and to identify clinical and laboratory parameters that are of value for diagnosing amebiasis in this patient group.

METHODS

The subjects were 111 patients (76 women, 35 men) with confirmed active ulcerative colitis who attended our hospital's Inflammatory Bowel Disease Outpatient Clinic between May 2002 and March 2006. In each case, a detailed medical history was collected, blood samples were tested for inflammatory markers, and stool samples were evaluated for presence of amebae using an Enzyme-Linked Immunosorbent Assay (ELISA) for detection of Entamoeba histolytica antigen. The clinical and laboratory variables for the ELISA-positive and ELISA-negative groups were compared.

RESULTS

Amebiasis was detected in 35 (31.5%) of the subjects. Patient age, disease duration, endoscopic activity index, serum C-reactive protein level, and white blood cell count were not useful for diagnosing amebiasis in this patient group.

CONCLUSIONS

Given the high rate of amebiasis observed in our patients with active ulcerative colitis, we recommend that, in Turkey any individual with ulcerative colitis who presents with symptoms of disease activation should be tested for ameba using antigen detection kits. A high index of suspicion is especially important in any region where E. histolytica is endemic.

[Autochthonous amebic liver abscess in Spain: an emerging disease? Case report and description of a PCR-based diagnostic test]

INTRODUCTION

In Spain an increase in cases of amebiasis has been detected in patients with no history of traveling to, or immigration from, endemic areas.

MATERIAL AND METHODS

This study describes two new cases of amebic hepatic abscess due to native protozoa and reviews 21 more cases of amebic hepatic abscess reported in Spanish patients who had never left the Iberian Peninsula. In addition, a new PCR-based technique for diagnosing Entamoeba histolytica is described.

RESULTS

Twenty cases (87%) occurred in men. The age range of the affected patients was 26 to 77 years. Two of the 3 women with extraintestinal amebiasis were HIV-positive. There was no history of exposure to the parasite in 17 cases. In the remaining 6 cases, direct contact with patients affected with amebiasis or with individuals or foods from endemic areas was recorded.

CONCLUSION

Entamoeba histolytica infection is becoming an emerging disease in our country. Amebiasis should be included in the differential diagnosis of consistent clinical entities even when there is no background of traveling or immigration. New molecular diagnostic tools can help to characterize this infection and should be considered reference techniques in combination with serological methods.

Development of loop-mediated isothermal amplification assay for detection of Entamoeba histolytica

A novel one-step, closed-tube, loop-mediated isothermal amplification (LAMP) assay for detecting Entamoeba histolytica, one of the leading causes of morbidity in developing countries, was developed. The sensitivity of the LAMP assay is 1 parasite per reaction. A total of 130 clinical samples were analyzed, and the results compared with those of conventional nested PCR to validate the practicability of this assay. No DNA was amplified from other diarrheal pathogens, such as other Entamoeba species, bacteria, and viruses. These results indicate that LAMP is a rapid, simple, and valuable diagnostic tool for epidemiological studies of amebiasis.

Development of a diagnostic PCR to detect Neoparamoeba perurans, agent of amoebic gill disease

The recent description of Neoparamoeba perurans as an aetiological agent of amoebic gill disease (AGD) advanced our understanding of the condition and has forced a re-evaluation of methods used for the diagnosis of AGD. Currently, there are no tools available that are both specific for N. perurans and suitable for a routine diagnostic procedure. Therefore, in this study we describe an assay to detect N. perurans. The assay, which utilizes PCR to amplify the N. perurans 18S rRNA gene, was shown to be specific and highly sensitive. Neoparamoeba perurans was detected in both gill samples and primary isolates of non-cultured gill-derived amoebae obtained during necropsy or biopsy from AGD-affected Atlantic salmon, Salmo salar L. The PCR-based assay provides a simple, flexible tool that will be a useful addition to the diagnostic repertoire for AGD. It may also be used for the genotypic screening of trophozoites during culture and could facilitate further epidemiological and ecological studies of AGD.

Laboratory diagnostic techniques for Entamoeba species

The genus Entamoeba contains many species, six of which (Entamoeba histolytica, Entamoeba dispar, Entamoeba moshkovskii, Entamoeba polecki, Entamoeba coli, and Entamoeba hartmanni) reside in the human intestinal lumen. Entamoeba histolytica is the causative agent of amebiasis and is considered a leading parasitic cause of death worldwide in humans. Although recent studies highlight the recovery of E. dispar and E. moshkovskii from patients with gastrointestinal symptoms, there is still no convincing evidence of a causal link between the presence of these two species and the symptoms of the host. New approaches to the identification of E. histolytica are based on detection of E. histolytica-specific antigen and DNA in stool and other clinical samples. Several molecular diagnostic tests, including conventional and real-time PCR, have been developed for the detection and differentiation of E. histolytica, E. dispar, and E. moshkovskii in clinical samples. The purpose of this review is to discuss different methods that exist for the identification of E. histolytica, E. dispar, and E. moshkovskii which are available to the clinical diagnostic laboratory. To address the need for a specific diagnostic test for amebiasis, a substantial amount of work has been carried out over the last decade in different parts of the world. The molecular diagnostic tests are increasingly being used for both clinical and research purposes. In order to minimize undue treatment of individuals infected with other species of Entamoeba such as E. dispar and E. moshkovskii, efforts have been made for specific diagnosis of E. histolytica infection and not to treat based simply on the microscopic examination of Entamoeba species in the stool. The incorporation of many new technologies into the diagnostic laboratory will lead to a better understanding of the public health problem and measures to control the disease.

Comparison of real-time PCR protocols for differential laboratory diagnosis of amebiasis

Specific identification of Entamoeba spp. in clinical specimens is an important confirmatory diagnostic step in the management of patients who may be infected with Entamoeba histolytica, the species that causes clinical amebiasis. Distinct real-time PCR protocols have recently been published for identification of E. histolytica and differentiation from the morphologically identical nonpathogenic Entamoeba dispar. In this study, we compared three E. histolytica real-time PCR techniques published by December 2004. The limits of detection and efficiency of each real-time PCR assay were determined using DNA extracted from stool samples spiked with serially diluted cultured E. histolytica trophozoites. The ability of each assay to correctly distinguish E. histolytica from E. dispar was evaluated with DNA extracted from patients' stools and liver aspirates submitted for confirmatory diagnosis. Real-time PCR allowed quantitative analysis of the spiked stool samples, but major differences in detection limits and assay performance were observed among the evaluated tests. These results illustrate the usefulness of comparative evaluations of diagnostic assays.

An improved PCR-based method for detection and differentiation of Entamoeba histolytica and Entamoeba dispar in formalin-fixed stools

Detection of infectious agents in faecal samples by polymerase chain reaction (PCR) can be limited by the presence of substances which inhibit DNA amplification. Here, an improved protocol is reported for directly isolating DNA from fresh and aged formalin-fixed stools, after concentration by formalin-ethyl acetate (FEA). The protocol was successfully applied to detect DNA of Entamoeba histolytica/Entamoeba dispar complex in stools by nested PCR, showing high specificity and low detection limit. Extended time of specimen storage in formalin had no influence on PCR yields. This PCR-based method offers technical advantages for routine detection and discrimination of invasive E. histolytica and non-invasive E. dispar.

Detection and genotyping of Entamoeba histolytica, Entamoeba dispar, Giardia lamblia, and Cryptosporidium parvum by oligonucleotide microarray

Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum are the most frequently identified protozoan parasites causing waterborne disease outbreaks. The morbidity and mortality associated with these intestinal parasitic infections warrant the development of rapid and accurate detection and genotyping methods to aid public health efforts aimed at preventing and controlling outbreaks. In this study, we describe the development of an oligonucleotide microarray capable of detecting and discriminating between E. histolytica, Entamoeba dispar, G. lamblia assemblages A and B, and C. parvum types 1 and 2 in a single assay. Unique hybridization patterns for each selected protozoan were generated by amplifying six to eight diagnostic sequences/organism by multiplex PCR; fluorescent labeling of the amplicons via primer extension; and subsequent hybridization to a set of genus-, species-, and subtype-specific covalently immobilized oligonucleotide probes. The profile-based specificity of this methodology not only permitted for the unequivocal identification of the six targeted species and subtypes, but also demonstrated its potential in identifying related species such as Cryptosporidium meleagridis and Cryptosporidium muris. In addition, sensitivity assays demonstrated lower detection limits of five trophozoites of G. lamblia. Taken together, the specificity and sensitivity of the microarray-based approach suggest that this methodology may provide a promising tool to detect and genotype protozoa from clinical and environmental samples.

Laboratory diagnosis of amebiasis

The detection of Entamoeba histolytica, the causative agent of amebiasis, is an important goal of the clinical microbiology laboratory. To assess the scope of E. histolytica infection, it is necessary to utilize accurate diagnostic tools. As more is discovered about the molecular and cell biology of E. histolytica, there is great potential for further understanding the pathogenesis of amebiasis. Molecular biology-based diagnosis may become the technique of choice in the future because establishment of these protozoa in culture is still not a routine clinical laboratory process. In all cases, combination of serologic tests with detection of the parasite (by antigen detection or PCR) offers the best approach to diagnosis, while PCR techniques remain impractical in many developing country settings. The detection of amebic markers in serum in patients with amebic colitis and liver abscess appears promising but is still only a research tool. On the other hand, stool antigen detection tests offer a practical, sensitive, and specific way for the clinical laboratory to detect intestinal E. histolytica. All the current tests suffer from the fact that the antigens detected are denatured by fixation of the stool specimen, limiting testing to fresh or frozen samples.

Development of a PCR-based method for diagnosis of Leishmania in blood samples

Visceral Leishmaniasis (VL) cases reported in Mediterranean countries and in Northern Europe are becoming increasingly frequent. The past few years several studies have shown Polymerase Chain Reaction to be more effective than the classical methods for the diagnosis of VL in clinical samples. The purpose of this study was the development of a simple, specific and sensitive PCR-based assay for the detection of Leishmania in blood samples. A specific pair of oligonucleotides was designed using conserved sequences of the ssu-rRNA Leishmania infantum gene. Of the 53 blood samples of patients suspected for leishmaniasis that were processed with the newly designed oligonucleotides, 13 were successfully diagnosed positive. The results were confirmed with sequencing and restriction fragment length polymorphism. The lower detection limit of the reported assay was 10 parasites per ml in all seeded samples tested and considered highly satisfactory for diagnosis of Leishmaniasis in blood samples.

Amebic Liver Abscess

Amebic liver abscess should be suspected in travelers returning from endemic areas or in immunocompromised patients who present with fever, right upper quadrant pain, hepatomegaly, and a liver lesion on an imaging study. Rapid initiation of therapy without serologic confirmation of infection, if necessary, is important to minimize complications. Metronidazole is given orally or intravenously for 14 days. The drug is generally well tolerated and leads to resolution of symptoms in most patients within 2 to 3 days. It is effective against luminal cysts in only 50% of patients and, therefore, must be followed by a course of treatment with paromomycin (Humatin; Parke-Davis, Morris Plains, NJ) or another luminal antiamebic agent to eradicate the parasite. Image-guided drainage of an amebic liver abscess is indicated in patients who do not respond to antimicrobial therapy or who are at risk of abscess rupture. Surgery is reserved for patients with a ruptured abscess. Although medical therapy is generally successful in the treatment of infection caused by Entamoeba histolytica, the development of potent vaccines will be needed for worldwide eradication of disease attributable to E. histolytica.

PCR as a diagnostic and quantitative technique in veterinary parasitology

Over the past 15 years, there has been a dramatic evolution in molecular approaches to study parasites and parasitic diseases. Many of these advancements have been brought about through the development of new applications of the polymerase chain reaction (PCR). Enhancements in sensitivity that can be achieved using PCR now permit scientists to investigate changes at the level of a single cell, far below what is often needed for parasite-derived applications. PCR has had a substantial impact on advances made in the areas of parasite systematics and epidemiology, immunology and host-parasite interactions, recombinant DNA vaccine development and most recently, the analysis of whole genomes either through directly sequencing the DNA, the analysis of expressed sequence tags (ESTs) or through the rapidly growing field of functional genomics. This paper, however, focuses on the application of PCR methodology to parasite detection and differentiation, and the diagnosis of disease. Specific attention is given to advances provided by multiplex PCR, fluorescence-based "real-time" PCR, and the utilization of PCR as a quantitative technique.

Parasitic infections of the intestine

Intestinal protozoal infections cause significant disease not only in the tropics but also in immunocompromised hosts and returning travellers in the developed world. Precise diagnosis of protozoal intestinal infection by microscopy can be difficult. Enzyme immunoassays for antigen detection are being used for some protozoal infections with some limitations which will, it is hoped, be overcome by molecular techniques. Nucleic acid amplification techniques could help improve detection of microsporidial species, which are difficult to detect microscopically and allow differentiation between Entamoeba histolytica and Entamoeba dispar. Definitive treatment for Cryptosporidium parvum infection remains elusive but new drugs are being evaluated. Cessation of thiabendazole production should not affect therapy of intestinal nematode infections as potent alternative therapy is available.

Microscopy, PCR and ELISA applied to the epidemiology of amoebiasis in Greece

Detection and differentiation between Entamoeba histolytica and E. dispar are of great importance both for diagnosis and epidemiological studies. The present study was aimed to estimate the prevalence of these species in Greece and to assess the performance of microscopy, ELISA and PCR in the field. Our results indicate that the prevalence of these parasites is very low in Greece and that PCR and ELISA are by far better than microscopy. When it comes to the choice between ELISA and PCR, it seems that in real situations the advantages of PCR are outweighed by those of ELISA.