Evaluation of Entamoeba histolytica antigen and antibody point-of-care tests for the rapid diagnosis of amebiasis

Investigation of Parasites in Food Handlers in Turkey

Increasing world population parallelly also brings an increase in food production and consumption. As food consumption increases, so do foodborne infections. In cases where adequate food safety and hygiene is not provided in places such as restaurants, dormitories, prisons, hospitals where mass feeding is made outside the home, many parasitic agents can be transmitted to people through food. People working in the food processing and distribution sector and who are in the position of porters play an important role in the spread of parasites, as they can transmit parasitic agents to food through fingernails and hands. Parasites such as Enterobius vermicularis, Entamoeba histolytica, and Giardia intestinalis can be transmitted to food and then to patients through nails and hands. This study was planned to investigate the presence of parasites in hospital food production and distribution workers, such as cooks and waiters, using various methods. Stool and serum samples were taken from 100 food production and distribution workers. Stool samples were examined by native-Lugol, concentration, trichrome, acid-fast staining, and cellophane tape methods. E. histolytica antigen in stool and Toxoplasma and Taenia antibodies in serum were searched by enzyme-linked immunosorbent assay. Parasites were detected in 59% people, and 41 were evaluated as negative. This positivity was 71.9% (23/32) in the 45-61 age range. Blastocystis sp. (27%), Toxoplasma (25%), E. histolytica (10%), Taenia spp. (7%), E. vermicularis (7%), Entamoeba coli (7%), G. intestinalis (5%), Chilomastix mesnili (1%), and I. butschlii (1%) were detected in food handlers. High Toxoplasma antibody positivity (25%) suggests the possibility of transmission to kitchen workers through ways, such as infected raw meat. However, the detection of E. histolytica, Taenia spp., E. vermicularis, G. intestinalis parasites in workers at significant levels poses a significant risk for society consuming these foods. As a result, it is important to investigate the presence of parasites in the employee dealing with food production and distribution to protect patients from parasitic infections especially in hospitals where the people are immunocompromised and more susceptible, and where mass meals are eaten.

Amebiasis and Amebic Liver Abscess in Children

Although rare in the developed world, amebiasis continues to be a leading cause of diarrhea and illness in developing nations with crowding, poor sanitation, and lack of clean water supply. Recent immigrants or travelers returning from endemic regions after a prolonged stay are at high risk of developing amebiasis. A high index of suspicion for amebiasis should be maintained for other high-risk groups like men having sex with men, people with AIDS/HIV, immunocompromised hosts, residents of mental health facility or group homes. Clinical presentation of intestinal amebiasis varies from diarrhea to colitis and dysentery. Amebic liver abscess (ALA) is the most common form of extraintestinal amebiasis. Various diagnostic tools are available and when amebiasis is suspected, a combination of stool tests and serology should be sent to maximize the yield of testing. Treatment with an amebicidal drug such as metronidazole/tinidazole and a luminal cysticidal agent such as paromomycin for clinical disease is indicated. However, for asymptomatic disease treatment with a luminal cysticidal agent to decrease chances of invasive disease and transmission is recommended.

Accurate laboratory diagnosis of human intestinal and extra-intestinal amoebiasis

Accurate diagnosis of Entamoeba histolytica is important, as it is known as a causative agent for both invasive intestinal and extra-intestinal amoebiasis. Amoebiasis has a worldwide distribution, especially in developing countries, and it is responsible for up to 100,000 fatal cases annually. A number of diagnostic methods, including microscopy, culture, antigen detection, molecular based methods, and serological assays have been proposed to assist in diagnosing amoebiasis. The present study aimed to gather new data and review the available diagnostic tests of both intestinal and extra-intestinal amoebiasis and to highlight pitfalls and challenges of each of them. A broad literature of electronic databases was conducted and covered articles published up to March 2022. For laboratory diagnosis of intestinal amoebiasis, direct microscopy stool examinations and cultures should be held as the high-performance diagnostic strategies. Molecular and immunological-based assays are also recommended as complementary tests. To diagnose extra-intestinal infection, the use of serological tests is still considered the method of choice. However, serodiagnosis requires further improvement for the accurate differential diagnosis of active infection from past infections.

Utility of the Rapid Antigen Detection Test E. histolytica Quik Chek for the Diagnosis of Entamoeba histolytica Infection in Nonendemic Situations

Entamoeba histolytica infection is an increasingly common sexually transmitted infection in Japan. Currently, stool ova and parasite examination (O&P) is the only approved diagnostic method. Here, we assessed the utility of the commercially available rapid antigen detection test (Quik Chek) for E. histolytica A multicenter cross-sectional study was conducted. Stool samples that had been submitted for O&P were included. The samples were subjected to both Quik Chek and PCR, and the Quik Chek results were assessed in comparison with PCR as the reference standard. E. histolytica infection was confirmed in 5.8% (38/657) of the samples and comprised 20 diarrheal and 18 nondiarrheal cases. The overall sensitivity and specificity of Quik Chek were 44.7% (95% confidence interval, 30.1 to 60.3) and 99.8% (99.1 to 100), respectively. The sensitivity of Quik Chek was higher for diarrheal cases (60.0%) than for nondiarrheal cases (27.8%). Furthermore, the combined use of Quik Chek with O&P increased the sensitivity (78.9%), especially for diarrheal cases (up to 90%). The E. histolytica burden assessed by quantitative PCR was similar between Quik Chek-positive and -negative samples. The Quik Chek assay sensitivity was lower for cyst-containing stools than for trophozoite-containing stools, although it was shown that cultured E. histolytica clinical strains from Quik Chek-negative cyst-containing stools exhibited antigenicity in vitro The present study confirmed the high specificity of Quik Chek for E. histolytica infection. Combined use with O&P increased the sensitivity of detection, facilitating the use of Quik Chek in point-of-care settings in nonendemic situations.

Giardia/Cryptosporidium QUIK CHEK Assay Is More Specific Than Quantitative Polymerase Chain Reaction for Rapid Point-of-care Diagnosis of Cryptosporidiosis in Infants in Bangladesh

Background

Cryptosporidium is a major cause of childhood diarrhea. Current modes of cryptosporidiosis diagnosis involve procedures that are costly and require both a well-equipped laboratory and technical expertise. Therefore, a cost-effective, user-friendly, and rapid method for point-of-care detection of Cryptosporidium is desirable.

Methods

A total of 832 diarrheal stool specimens collected from 200 children aged <2 years were tested by Giardia/Cryptosporidium QUIK CHEK, enzyme-linked immunosorbent assay (ELISA), and quantitative polymerase chain reaction (qPCR) to compare the performance of the individual techniques. We also tested for the presence of other diarrheal pathogens in qPCR-positive samples with a TaqMan Array Card (TAC) to assess whether Cryptosporidium was the sole causative agent for the diarrheal episodes.

Results

Of 832 samples, 4.4% were found positive for Cryptosporidium by QUIK CHEK, 3.6% by ELISA, and 8.8% by qPCR. Using TAC-attributed Cryptosporidium diarrhea as the gold standard, the sensitivities of QUIK CHEK, ELISA, and qPCR were 92.3%, 71.8%, and 100%, respectively; the specificities were 97.1%, 94.3%, and 0%, respectively. Analysis of the qPCR-positive and QUIK CHEK-negative samples by TAC identified other enteropathogens as more likely than Cryptosporidium to be the causative agents of diarrhea.

Conclusions

QUIK CHEK was more sensitive and specific than ELISA. While qPCR detected Cryptosporidium in more samples than QUIK CHEK, most of these were instances of qPCR detecting small quantities of Cryptosporidium DNA in a diarrheal episode caused by another enteropathogen. We concluded that QUIK CHEK was comparable in sensitivity and superior in specificity to qPCR for the diagnosis of Cryptosporidium diarrhea.

Indirect Haemagglutination Test in Comparison with ELISA for Detection of Antibodies against Invasive Amoebiasis

INTRODUCTION

Diagnosis of amoebiasis is based on combination of tests like microscopy, imaging, serology and molecular methods. In absence of molecular techniques, serology can be used as an alternative aid. Various serological techniques were reported with different sensitivity and specificity. The diagnostic efficiency of these assays mainly depends on the characteristics of antigen that is being used and various conditions of performance.

AIM

To evaluate the efficiency of recombinant calcium binding domain containing protein by Indirect Haemagglutination Assay (IHA) against a commercial ELISA among amoebic liver abscess cases and control group.

MATERIALS AND METHODS

The study was carried out during the period of 2011-2015 and blood samples were collected from suspected amoebiasis cases who were attending the clinics of Medicine and Paediatrics department, JIPMER. A total of 200 sera samples which included 100 Amoebic Liver Abscess (ALA), 50 cases of other parasitic infections and liver diseases and 50 presumed healthy controls were examined by IHA and commercial ELISA. In brief, chick cells were stabilized by Double Aldehyde Sensitization (DAS) method. Optimum Sensitizing Dose (OSD) of the antigen was determined. The test was performed in a U-bottomed microtiter plate with recombinant amoebic antigen (12.5μg/ml), incubated at Room Temperature (RT) for 2 hours. RIDASCREEN Entamoeba IgG ELISA kit which is commercially available was used to evaluate the samples as per manufacturer's instruction.

RESULTS

The overall sensitivity and specificity of the IHA was 62% and 96%, respectively when compared to ELISA having sensitivity and specificity of 69% and 90%, respectively. The positive predictive value of the IHA was 91% while negative predictive value was 79%. Similarly, the positive predictive value of the ELISA was 87% while negative predictive value was 74%.

CONCLUSION

As serology heavily suffers due to lack of a standardised test system employing the native antigen, there arises need to identify alternative source of recombinant antigen which could effectively improvise the existing lacunae in the current system. Serology acts as an adjunct in clinical decision making if properly interpreted. This is an important consideration in endemic region where health services resources are limited.

Seroprevalence of Entamoeba histolytica from a tertiary care hospital, South India

INTRODUCTION

Amebiasis is the third leading cause of death after malaria and schistosomiasis. Diagnosis is based on microscopy, culture, isoenzyme analysis, and serology-based techniques. In resource-limited nation such as India where polymerase chain reaction cannot be employed, serology is considered to be the reliable diagnostic tool. To find the seroprevalence of Entamoeba histolytica IgG antibody by enzyme-linked immunosorbent assay (ELISA) among the liver abscess cases and healthy controls.

MATERIALS AND METHODS

Commercially available RIDASCREEN Entamoeba IgG ELISA kit was used to evaluate the samples as per manufacturer's instruction.

RESULTS

A total of 322 samples were evaluated by ELISA. 94/157 (59.87%) were positive for amebic liver abscess cases, 2/13 (15.38%) were positive in suspected amebiasis group, 5/15 (33.3%) were positive in nonamoebic hepatic disorder group, 5/39 (12.8%) were positive in other parasitic disorders, and 2/98 (2.04%) were positive in presumed healthy controls. The sensitivity and specificity of the assay were found to be 56% and 92%, respectively.

CONCLUSION

In an endemic nation such as India and other developing countries, ELISA can be used as a routine surveillance test in a clinical setup to detect amoebiasis if the cases are judicially evaluated along with the other routine tests.

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.

Production of recombinant Entamoeba histolytica pyruvate phosphate dikinase and its application in a lateral flow dipstick test for amoebic liver abscess

BACKGROUND

Amoebic liver abscess (ALA) is the most common clinical manifestation of extraintestinal amoebiasis especially in developing countries, causing up to 100 000 fatal cases annually. Accurate and early diagnosis is important to prevent the disease complications, however its diagnosis still poses many challenges due to the limitations of the available detection tools. Pyruvate phosphate dikinase (PPDK), an excretory-secretory protein of E. histolytica, has been reported as a potential diagnostic marker for ALA, hence it may be exploited in the development of a new test for ALA.

METHODS

Recombinant PPDK (rPPDK) was expressed, purified and evaluated by Western blot. In parallel, recombinant galactose-and-N-acetyl-D-galactosamine inhibitable lectin (Gal/GalNAc lectin) was produced and tested similarly. The protein identity was confirmed by analysis using MALDI-TOF/TOF. A lateral flow dipstick (LFD) test using rPPDK was subsequently developed (rPPDK-LFD) and evaluated for serodiagnosis of ALA.

RESULTS

rPPDK was expressed as soluble protein after 4 hours of induction with 1 mM isopropyl β-D-1-thiogalactopyranoside (IPTG) at 30°C. Purification using nickel-nitrilotriacetic acid (Ni-NTA) resin yielded 1.5 mg of rPPDK from 1 L of culture with estimated molecular mass of 98 kDa on SDS-PAGE. Western blots using sera from patients with ALA, healthy individuals and other diseases probed with anti-human IgG4-HRP showed the highest sensitivity (93.3%) and specificity (100%); as compared to blots using IgG and IgG1 as secondary antibodies. Moreover, rPPDK showed better specificity when compared to rGal/GalNAc lectin. In the development of the LFD test, the optimum amount of rPPDK was 0.625 μg per dipstick and the optimum working concentration of colloidal gold conjugated anti-human IgG4 was optical density (OD) 5 (1.7 μg of anti-human IgG4). Evaluation of rPPDK-LFD using ALA patients and controls serum samples showed 87% diagnostic sensitivity and 100% specificity.

CONCLUSION

The developed rPPDK-LFD showed good potential for rapid diagnosis of ALA, and merit further multicentre validation using larger number of serum samples.

Longitudinal evaluation of enteric protozoa in Haitian children by stool exam and multiplex serologic assay

Haitian children were monitored longitudinally in a filariasis study. Included were stool samples examined for Giardia intestinalis and Entamoeba histolytica cysts, and serum specimens analyzed for immunoglobulin G (IgG) responses to eight recombinant antigens from G. intestinalis (variant-specific surface protein [VSP1-VSP5]), E. histolytica (lectin adhesion molecule [LecA]), and Cryptosporidium parvum (17- and 27-kDa) using a multiplex bead assay. The IgG responses to VSP antigens peaked at 2 years of age and then diminished and were significantly lower (P < 0.002) in children > 4.5 years than in children < 4.5 years. The IgG responses to Cryptosporidium tended to increase with age. The IgG responses to LecA and VSP antigens and the prevalence of stools positive for cysts were significantly higher (P < 0.037 and P < 0.035, respectively) in the rainy season than in the dry season. The multiplex bead assay provides a powerful tool for analyzing serologic responses to multiple pathogens.

Decreasing intestinal parasites in recent Northern California refugees

Beginning in 2005, the Centers for Disease Control and Prevention (CDC) expanded the overseas presumptive treatment of intestinal parasites with albendazole to include refugees from the Middle East. We surveyed the prevalence of helminths and protozoa in recent Middle Eastern refugees (2008-2010) in comparison with refugees from other geographical regions and from a previous survey (2001-2004) in Santa Clara County, California. Based on stool microscopy, helminth infections decreased, particularly in Middle Eastern refugees (0.1% versus 2.3% 2001-2004, P = 0.01). Among all refugees, Giardia intestinalis was the most common protozoan found. Protozoa infections also decreased somewhat in Middle Eastern refugees (7.2%, 2008-2010 versus 12.9%, 2001-2004, P = 0.08). Serology for Strongyloides stercoralis and Schistosoma spp. identified more infected individuals than stool exams. Helminth infections are increasingly rare in refugees to Northern California. Routine screening stool microscopy may be unnecessary in all refugees.

Evaluation of a rapid point-of-care fecal antigen detection test for Entamoeba histolytica

Amebiasis is a major cause of morbidity and mortality in the developing world. A reliable point-of-care test would help to improve diagnosis and early treatment. We evaluated a novel rapid fecal antigen detection test for E. histolytica (E. HISTOLYTICA QUIK CHEK; TechLab, Inc., Blacksburg, VA), in a cohort of children in Bangladesh where amebiasis is endemic. This point-of-care test had a sensitivity of 100% and a specificity of 100% when compared with enzyme-linked immunosorbent assay antigen detection.

Evaluation of rapid antigen point-of-care tests for detection of Giardia and Cryptosporidium species in human fecal specimens

In Bangladesh, a new parasite rapid antigen test was investigated demonstrating accuracy and feasibility. For Giardia species, it had a sensitivity and specificity of 94% and 100%, respectively. For Cryptosporidium species, it had a sensitivity and specificity of 100% and 100%, respectively. These are higher than or equal to the sensitivities and specificities of other tests on the market.

Rapid Diagnosis of Intestinal Parasitic Protozoa, with a Focus on Entamoeba histolytica

Entamoeba histolytica is an invasive intestinal pathogenic parasitic protozoan that causes amebiasis. It must be distinguished from Entamoeba dispar and E. moshkovskii, nonpathogenic commensal parasites of the human gut lumen that are morphologically identical to E. histolytica. Detection of specific E. histolytica antigens in stools is a fast, sensitive technique that should be considered as the method of choice. Stool real-time PCR is a highly sensitive and specific technique but its high cost make it unsuitable for use in endemic areas where there are economic constraints. Serology is an important component of the diagnosis of intestinal and especially extraintestinal amebiasis as it is a sensitive test that complements the detection of the parasite antigens or DNA. Circulating Gal/GalNac lectin antigens can be detected in the serum of patients with untreated amoebic liver abscess. On the horizon are multiplex real-time PCR assays which permit the identification of multiple enteropathogens with high sensitivity and specificity.

Evaluation of a screening test for detection of giardia and cryptosporidium parasites

The Giardia/Cryptosporidium Chek test (TechLab, Inc.), a screening test for Giardia and Cryptosporidium, was evaluated with 136 fecal samples. Using the results of the Giardia II test and Cryptosporidium II test as gold standards, it was 98.4% sensitive and 100% specific and had positive and negative predictive values of 98.7% and 99.3%.

Amebic colitis: new insights into pathogenesis and treatment

Amebiasis, caused by the protozoan parasite Entamoeba histolytica, affects more than 50 million people worldwide, with over 100,000 deaths annually. The majority of cases are asymptomatic; however, significant morbidity and mortality are associated with illness in the remaining 10% of cases. Recent advances in the understanding of the mechanism of infection by E. histolytica, the role of the innate immune system, and the role of genetic disposition to infection will allow the development of novel detection and treatment methods. The disease mechanisms, clinical findings, therapeutic strategies, and important developments regarding amebiasis are discussed here.