Specific detection of Entamoeba histolytica DNA by hemolysin gene targeted PCR

Real-time loop-mediated isothermal amplification (real-time LAMP) assay for rapid diagnosis of amoebic liver abscess

Among the parasitic diseases, amoebic liver abscess (ALA) ranks second to malaria in terms of mortality. Due to the poor sensitivity of conventional diagnostic methods, there is a need for the development of effective and rapid diagnostic methods for ALA. Thus, the purpose of this work was to develop a real-time loop-mediated isothermal amplification (RT-LAMP) assay specific to Entamoeba histolytica. Further, we compared the performance of real-time LAMP with conventional and real-time PCR (RT-PCR) targeting 18S small subunit ribosomal RNA (18S SSU rRNA) gene of E. histolytica in patients with ALA. A total of 126 liver samples were obtained for the study. Of these, 96 aspirated pus samples were obtained from patients suffering from an ALA (serology confirmed, anti-amoebic immunoglobulin IgG positive), 19 aspirated pus samples from patients with pyogenic liver abscess (PLA, 16S RNA gene positive) and 11 autopsy liver tissues. The results showed that the DNA of E. histolytica was detected in 81 samples by conventional PCR, 93 by RT-PCR and 95 by RT-LAMP. The analytical sensitivity of the RT-LAMP assay was much higher than the other two techniques. RT-LAMP assay was able to amplify up to one copy of the targeted gene of E. histolytica while conventional PCR and RT-PCR could amplify up to 103 and 102 copies of the targeted gene of E. histolytica, respectively. In conclusion, RT-LAMP proved to be a sensitive, specific and rapid test which can be utilised as an effective tool for the diagnosis of ALA.

Molecular Dissection of Phagocytosis by Proteomic Analysis in Entamoeba histolytica

Entamoeba histolytica is the enteric protozoan parasite responsible for amebiasis. Trophozoites of E. histolytica ingest human cells in the intestine and other organs, which is the hallmark of its pathogenesis. Phagocytosis and trogocytosis are pivotal biological functions for its virulence and also contribute to the proliferation of nutrient uptake from the environment. We previously elucidated the role of a variety of proteins associated with phagocytosis and trogocytosis, including Rab small GTPases, Rab effectors, including retromer, phosphoinositide-binding proteins, lysosomal hydrolase receptors, protein kinases, and cytoskeletal proteins. However, a number of proteins involved in phagocytosis and trogocytosis remain to be identified, and mechanistic details of their involvement must be elucidated at the molecular level. To date, a number of studies in which a repertoire of proteins associated with phagosomes and potentially involved in phagocytosis have been conducted. In this review, we revisited all phagosome proteome studies we previously conducted in order to reiterate information on the proteome of phagosomes. We demonstrated the core set of constitutive phagosomal proteins and also the set of phagosomal proteins recruited only transiently or in condition-dependent fashions. The catalogs of phagosome proteomes resulting from such analyses can be a useful source of information for future mechanistic studies as well as for confirming or excluding a possibility of whether a protein of interest in various investigations is likely or is potentially involved in phagocytosis and phagosome biogenesis.

Molecular epidemiology, evolution, and phylogeny of Entamoeba spp

Entamoeba histolytica is a protozoan parasite and the causative agent of amoebiasis in humans. The estimations of the worldwide burden of amoebiasis by the WHO indicated that approximately 500 million people were infected with the parasite and 10% of these individuals had invasive amoebiasis. However, our understanding of the disease burden and epidemiology of human amebiasis has undergone dramatic changes over the last two decades based on molecular analyses. The development of Entamoeba genomics has also provided some interesting and valuable information on the evolution and population structure of this parasite. In addition, the use of a number of molecular markers has greatly expanded our understanding of Entamoeba host range and genetic diversity. In this review, we re-assessed Entamoeba prevalence and species in humans, non-human primates, other animals, and the environment in the context of molecular data. Some issues regarding the evolution and phylogeny of different Entamoeba species lineages are also discussed.

Underestimated Amoebic Appendicitis among HIV-1-Infected Individuals in Japan

Entamoeba histolytica is not a common causative agent of acute appendicitis. However, amoebic appendicitis can sometimes be severe and life threatening, mainly due to a lack of awareness. Also, its frequency, clinical features, and pathogenesis remain unclear. The study subjects were HIV-1-infected individuals who presented with acute appendicitis and later underwent appendectomy at our hospital between 1996 and 2014. Formalin-fixed paraffin-embedded preserved appendix specimens were reexamined by periodic acid-Schiff (PAS) staining and PCR to identify undiagnosed amoebic appendicitis. Appendectomies were performed in 57 patients with acute appendicitis. The seroprevalence of E. histolytica was 33% (14/43) from the available stored sera. Based on the medical records, only 3 cases were clinically diagnosed as amoebic appendicitis, including 2 diagnosed at the time of appendectomy and 1 case diagnosed by rereview of the appendix after the development of postoperative complications. Retrospective analyses using PAS staining and PCR identified 3 and 3 more cases, respectively. Thus, E. histolytica infection was confirmed in 9 cases (15.8%) in the present study. Apart from a significantly higher leukocyte count in E. histolytica-positive patients than in negative patients (median, 13,760 versus 10,385 cells/μl, respectively, P = 0.02), there were no other differences in the clinical features of the PCR-positive and -negative groups. In conclusion, E. histolytica infection was confirmed in 9 (15.8%) of the appendicitis cases. However, only 3, including one diagnosed after intestinal perforation, were diagnosed before the present analyses. These results strongly suggest there is frequently a failure to detect trophozoites in routine examination, resulting in an underestimation of the incidence of amoebic appendicitis.

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

OBJECTIVE

To develop a loop-mediated isothermal amplification (LAMP) assay for the detection of Entamoeba histolytica E. histolytica, the causative agent of amebiasis.

METHODS

The LAMP primer set was designed from E. histolytica hemolysin gene HLY6. Genomic DNA of E. histolytica trophozoites strain HK9 was used to optimize the LAMP mixture and conditions. Amplification of DNA in the LAMP mixture was monitored through visual inspection for turbidity of the LAMP mix as well as addition of fluorescent dye.

RESULTS

Positive LAMP reactions turned turbid while negative ones remained clear. Upon addition of a fluorescent dye, all positive reactions turned green while the negative control remained orange under ambient light. After electrophoresis in 1.5% agarose gels, a ladder of multiple bands of different sizes can be observed in positive samples while no bands were detected in the negative control. The sensitivity of the assay was found to be 5 parasites per reaction which corresponds to approximately 15.8 ng/μ L DNA. The specificity of the assay was verified by the absence of amplified products when DNA from other gastrointestinal parasites such as the morphologically similar but non-pathogenic species, Entamoeba dispar 39, and other diarrhea-causing organisms such as Blastocystis hominis and Escherichia coli were used.

CONCLUSIONS

The LAMP assay we have developed enables the detection of E. histolytica with rapidity and ease, therefore rendering it is suitable for laboratory and field diagnosis of amebiasis.

Evaluation of antigen detection and polymerase chain reaction for diagnosis of amoebic liver abscess in patients on anti-amoebic treatment

BACKGROUND

Diagnosis of amoebic liver abscess (ALA) in patients on anti-amoebic drugs is difficult. There is scanty data on this issue using Entamoeba histolytica (E. histolytica) lectin antigen and polymerase chain reaction (PCR). We studied utility of lectin antigen, PCR, and IgG antibody in diagnosis of liver abscess in patients on anti-amoebic treatment. Liver aspirate of 200 patients, of which 170 had anti-amoebic drug prior to drainage, was tested for E. histolytica lectin antigen by (ELISA), PCR, bacterial culture, and serum IgG antibody by (ELISA). Classification of abscesses was based on result of anti-amoebic IgG antibody and bacterial culture, E. histolytica PCR and bacterial culture, and E. histolytica lectin antigen and bacterial culture.

FINDINGS

Using anti-amoebic IgG antibody and bacterial culture, 136/200 (68.0%) were classified as ALA, 12/200 (6.0%) as pyogenic liver abscess (PLA), 29/200 (14.5%) as mixed infection, and 23/200 (11.5%) remained unclassified. Using amoebic PCR and bacterial culture 151/200 (75.5%) were classified as ALA, 25/200 (12.5%) as PLA, 16/200 (8.0%) as mixed infection, and 8/200 (4.0%) remained unclassified. With E. histolytica lectin antigen and bacterial culture, 22/200 (11.0%) patients were classified as ALA, 39/200 (19.5%) as PLA, 2/200 (1.0%) as mixed infection, and 137/200 (68.5%) remained unclassified.

CONCLUSIONS

E. histolytica lectin antigen was not suitable for classification of ALA patients who had prior anti-amoebic treatment. However, PCR may be used as alternative test to anti-amoebic antibody in diagnosis of ALA.

PCR diagnosis of Entamoeba histolytica cysts in stool samples

Amebiasis is a protozoan disease caused by Entamoeba histolytica and a potential health threat in areas where sanitation and hygiene are inappropriate. Highly sensitive PCR methods for detection of E. histolytica in clinical and environmental samples are extremely useful to control amebiasis and to promote public health. The present study compared several primer sets for small subunit (SSU) rDNA and histone genes of E. histolytica cysts. A 246 bp of the SSU rDNA gene of pure cysts contained in phosphate-buffered saline (PBS) and in stool samples was successfully amplified by nested PCR, using the 1,147-246 bp primer set, of the primary PCR products which were pre-amplified using the 1,147 bp primer as the template. The detection limit of the nested PCR using the 1,147-246 primer set was 10 cysts in both groups (PBS and stool samples). The PCR to detect histone gene showed negative results. We propose that the nested PCR technique to detect SSU rDNA can be used as a highly sensitive genetic method to detect E. histolytica cysts in stool samples.

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.

Differentiation of Entamoeba histolytica from Entamoeba dispar by PCR-coupled nonisotopic SSCP analysis

Entamoeba histolytica is a pathogenic protozoan parasite, which causes amoebic colitis, dysentery and liver abscesses in humans. Since the cyst and small trophozoite stages of this parasite are indistinguishable by light microscopy from Entamoeba dispar (which is nonpathogenic), specific diagnosis is compromised. To overcome this limitation, a PCR-coupled SSCP approach, utilising a sequence difference of 4.6% in a short region ( approximately 173-174 bp) of the small subunit of nuclear ribosomal DNA, was evaluated for the differentiation of the two species of Entamoeba. Including a range of well-defined control DNA samples (n = 67) to evaluate the specificity of the PCR, 45 DNA samples representing E. histolytica and E. dispar from human faecal samples were tested by SSCP, and unequivocal delineation between the species was achieved. This SSCP approach should provide a practical tool for the specific diagnosis of E. histolytica in humans and for investigating its epidemiology.

Entamoeba histolytica and Entamoeba dispar: comparison of two PCR assays for diagnosis in a non-endemic setting

Detection of Entamoeba histolytica, the causative agent of amoebiasis, is an important goal of the clinical parasitology laboratory. The identification of Entamoeba dispar as a morphologically identical but non-pathogenic species has highlighted the need for non-microscopic detection methods able to differentiate between the two organisms. In this study we evaluated the utility of conventional PCR and real-time PCR as methods for identification and differentiation of E. histolytica and E. dispar. The second aim of this study was to determine the relative proportions of infections caused by E. histolytica and the non-pathogenic E. dispar, allowing a picture of the epidemiological situation in a non-endemic setting to be obtained. One hundred and sixty-six clinical samples (faecal and liver abscess samples and one intestinal biopsy) belonging to 108 patients were analysed. More patients with E. dispar infection (8.3%) than patients with E. histolytica infection (5.6%) were found by both PCR assays. It is concluded that routine diagnosis of invasive amoebiasis performed by a combination of microscopy, culture and serology should be complemented with a PCR assay such as real-time PCR that offers a practical and clinically acceptable alternative for rapid and accurate diagnosis of amoebic infection in patients presenting with symptoms indicative of this disease.

Amebic liver abscess

Amebic liver abscess is the most common extraintestinal manifestation of infection with Entamoeba histolytica, and it is associated with significant morbidity and mortality. In this article the most recent available information is reviewed relating to epidemiology, pathogenesis, presentation, diagnosis, and treatment. We reviewed thousands of cases of amebic liver abscess in the medical literature and present that information as it pertains to mortality, gender, anatomic location of abscesses, and clinical signs and symptoms.