Public health and clinical importance of amoebiasis in Malaysia: a review

Entamoeba histolytica, the causative agent of human amoebiasis remains a significant cause of morbidity and mortality in developing countries and is responsible for up to 100,000 deaths worldwide each year. Entamoeba dispar, morphologically indistinguishable from E. histolytica is more common in humans in many parts of the world. Similarly Entamoeba moshkovskii, which was long considered to be a free-living amoeba is also morphologically identical to E. histolytica and E. dispar, and is highly prevalent in some E. histolytica endemic countries. Humans are the host of infection and there would not appear to be other meaningful animal reservoirs of E. histolytica. Entamoeba. histolytica can be present in sewage and contaminated water. The infection is mainly transmitted via ingestion of water or food contaminated by faeces containing E. histolytica cysts. Clinical features of amoebiasis range from asymptomatic colonization to amoebic dysentery and invasive extraintestinal amoebiasis, which is manifested most commonly in the form of abscesses in liver and lungs. The epidemiology of amoebiasis has dramatically changed since the separation of E. histolytica and E. dispar species and the worldwide prevalence of these species has not been estimated until recently. Morever, E. moshkovskii, another morphologically indistinguishable human parasitic Entamoeba was not mentioned or considered as a contributor to the prevalence figures in endemic areas. Amoebiasis is still a major health problem especially in aboriginal settlements and amongst people living in remote area in Malaysia. However, until now there is only one data currently available to indicate the true prevalence and incidence of E. histolytica and E. dispar. Further studies are needed to determine the burden of E. histolytica, E. dispar and E. moshkovskii infections in Malaysia. In the present review, we briefly summarize all methods use in diagnosing Entamoeba species, ranging from microscopic identification to molecular detection such as culture and isoenzyme analysis, antibody detection tests, antigen detection tests, immunochromatographic assays, conventional PCR, real-time PCR and loop-mediated isothermal amplification (LAMP).

Use of PCR to detect Entamoeba gingivalis in diseased gingival pockets and demonstrate its absence in healthy gingival sites

Investigators using light microscopy have identified the protozoan parasite Entamoeba gingivalis from diseased gingival pockets for nearly 100 years. The objective of the present investigation was to develop a molecular biology approach for determining the presence of E. gingivalis in both diseased gingival pockets and healthy gingival sites. For this, a previously developed conventional polymerase chain reaction (PCR) was evaluated and a real-time polymerase chain reaction assay was developed. Paper points were inserted into the base of the sulcus of both diseased gingival pockets and healthy gingival sites. DNA was extracted using the QIAamp DNA mini kit, and subsequently analyzed using conventional and real-time PCR analysis. A previously described primer set specific for the small subunit ribosomal RNA gene (SSU rDNA) of E. gingivalis was used for the conventional PCR. For the real-time PCR, a primer set was designed to amplify a 135-bp fragment inside the SSU rDNA of E. gingivalis. A conventional PCR assay detected E. gingivalis in 27% of diseased gingival pockets. The real-time PCR using a different primer set detected protozoa in 69% of diseased pocket sites. Thus, the latter technique proved more sensitive for detection of E. gingivalis. No E. gingivalis were detected in any of the healthy gingival pocket sites using either type of PCR assay. Results support a concept that the presence of E. gingivalis is associated only with diseased gingival pocket sites. The newly described methodology may also serve to provide a novel eukaryotic cell marker of disease status in gingival pockets.

Pathogen destruction and solids decomposition in composting latrines: study of fundamental mechanisms and user operation in rural Panama

The relationship between temperature, high pH, desiccation, decomposition, pathogen destruction, and user operation in active double vault urine diverting (DVUD) composting latrines located in the Bocas del Toro region of Panama was assessed. Latrine samples were analyzed for temperature, pH, % moisture, carbon-to-nitrogen (C/N) ratio, and presence of specific pathogens. Surveys and visual inspections were used to verify use and type of dry material desiccant added. Measurements supported findings that compost latrines do not reach temperatures sufficient to destroy all pathogens. pH measurements showed that many latrines were operating within the range for ideal aerobic decomposition, a pH of 7.5-8.5, but only 17% of latrines measured pH 9 or above. Almost 100% of composting latrine users added sawdust and wood ash, to lower moisture level and provide carbon for decomposition. However, the recommended amount of desiccant added was insufficient to reduce moisture to the suggested 25% for pathogen destruction and C/N ratios remained in the range of raw human faeces. Importantly, pathogens, mainly helminths, were still present in compost stored for the 6-month contact time. The latrines have conflicting goals of pathogen destruction and aerobic decomposition. Recommendations are made regarding operation of composting latrines and disposal of composted material.

Validation and utilization of PCR for differential diagnosis and prevalence determination of Entamoeba histolytica/Entamoeba dispar in Salvador City, Brazil

Amoebiasis is an infection caused by Entamoeba histolytica and is a potential health risk in countries in which health barriers are inappropriate. Since the discovery of Entamoeba dispar, the prevalence of amoebiasis has been modified.

OBJECTIVE

This study has standardized the PCR technique applied for the diagnosis of different species of the E. histolytica/E. dispar complex and has evaluated the prevalence of infection among patients attending private and public clinical laboratories in Salvador City, Bahia State, Brazil.

RESULTS

Analysis of 52,704 stool samples by microscopic examination demonstrated that 1,788 (3.4%) were positive for the E. histolytica/E. dispar complex and infection occurred more often in samples originated from public clinical laboratories (5.0%) than those that came from private laboratories (3.2%). PCR performed in approximately 15% (262) E. histolytica/E. dispar complex positive samples, randomly chosen, amplified 227 samples (86.6%), all of them positive for E. dispar. The non-amplified 35 samples (13.4%) were also negative for E. histolytica-specific galactose adhesin. Moreover, to exclude a probable infection caused by E. hartmanni, morphometric analysis demonstrated that non-amplified samples had cyst sizes comparable to E. histolytica/E. dispar (>10 µm).

CONCLUSION

The absence of amplification of these samples indicates the presence of PCR inhibitors in the stool samples or the presence of DNA from Entamoeba species other than E. dispar, E. histolytica or E. hartmanni.

[Investigation of intestinal parasites among elementary school students in the Mugla province]

OBJECTIVE

In this study prevalence of intestinal parasite agents was investigated among elementary school students in the Mugla city centre.

METHODS

Only 663 relatives among 3560 students allowed us to investigate and obtain fecal specimens of the students. Specimens were examined by native and lugol staining. Repeated samples were requested from suspected cases and evaluated.

RESULTS

Intestinal parasites were found in 73 stool specimens (11.01%) taken from students. The frequently observed parasite was Ascaris lumbricoides at ratio of 52% (39 students).

CONCLUSION

It was estimated that, because of the lack of a sewage system in the Mugla province, health education and periodically parasite examinations should be administered to elementary school students and their families in order to raise awareness and prevent parasitic infections.

Parasitological stool examination from children without the typical symptoms of parasitic disease

Most parasitic intestinal infestations in humans are sub-clinical and, therefore, they are rarely diagnosed. A number of general, non-specific symptoms of parasitic invasions are often attributed to other diseases. A parasitological examination of feces performed as part of this study confirmed the presence of intestinal parasites in 21.6% of samples. Among the patients who reported 6 different symptoms, the percentage of parasite-positive samples reached 80%. The obtained results suggest that coproscopic tests may establish the diagnosis in unclear cases, particularly in children. Many parasitic invasions are zoonoses and pets owe a reservoir. In view of the above, the results for pet owners and non-pet owners were compared in the study. There was no direct correlation between pet ownership and the incidence of parasitic infections.

[Amebiasis: implications of the recognition of Entamoeba dispar and the identification of Entamoeba moshkovskii in humans]

The history of Entamoeba histolytica is very confuse and shows several wrong concepts about the parasite and its relationship with the host. The poor correlation between the prevalence of asymptomatic and symptomatic amebiasis originated the proposal of three explicative hypothesis, among them was the concept of Brumpt that E. histolytica comprised two morphologically identical species, E. dysenteriae and E. dispar. The application of modern molecular techniques irrefutably proved that E. histolytica was really a complex of two species, confirming the concept of Brumpt almost 7 decades later. Recent studies have identified in humans E. moshkovskii, morphologically indistinguishable from E. histolytica and E. dispar, a great genetic diversity within each of these species, and heterogeneity in virulence among E. histolytica strains. The redescription of E. dispar, and the recovery of E. moshkovskii from humans have had a major impact in our understanding of E. histolytica and amebiasis with important clinical and epidemiologic implications. This has led to the need of a reevaluation of the infection in terms of prevalence and morbidity in the global population and to study the geographic distribution, prevalence, and transmission pattern of E. histolytica strains in order to detect those with epidemiologic relevance and predict the risk of amebic disease in a population.

Discrimination of Entamoeba moshkovskii in patients with gastrointestinal disorders by single-round PCR

Entamoeba moshkovskii and Entamoeba dispar are impossible to differentiate microscopically from the pathogenic species Entamoeba histolytica. There are limited data on the prevalence of these commensal parasites in Iran. We utilized a single-round PCR assay to determine the prevalence of E. moshkovskii, E. dispar, and E. histolytica in stool samples from Iranian patients infected with gastrointestinal disorders. After culturing of microscopy-positive isolates and extraction of DNA, PCR was carried out to differentiate the Entamoeba isolates. Out of 3,825 stool samples examined by microscopy, 58 specimens (1.52%) were infected with E. histolytica, E. dispar, or E. moshkovskii. By PCR, 2 E. histolytica (3.45%), 53 E. dispar (91.37%), 2 E. moshkovskii (3.45%), and one mixed E. dispar/E. moshkovskii infection (1.73%) were detected. In view of the reporting of E. moshkovskii in this study in Iran and the difficulty in discriminating this ameba from two similar Entamoeba spp. by microscopy, we recommend the single-round PCR assay as an alternative tool in routine diagnosis and in epidemiological studies of amebiasis.

[The distribution of intestinal parasites detected in The Dokuz Eylul University Medical Faculty Hospital between 2005 and 2008.]

A retrospective evaluation of the data from 14,246 patients with gastrointestinal complaints who presented at the parasitology laboratory of the Dokuz Eylul University Medical Faculty Hospital between January 2005 and December 2008 was carried out. Fecal samples of all patients were examined using native-Lugol and the trichrome and Kinyoun acid-fast staining method after sedimentation in fecal concentration tubes. One or more parasites were detected in 1320 (9.3%) of the patients. The distribution of the intestinal parasites was as follows: Blastocystis hominis, 689 (4.83%); nonpathogenic amoebas, 108 (21.82%); Giardia intestinalis, 320 (2.24%); Enterobius vermicularis, 23 (0.16%); Entamoeba histolytica/Entamoeba dispar, 34 (0.24%); and other rare parasites, 78 (0.54%). The results of this study emphasize the fact that intestinal parasitic infections are still an important public health problem.

[The investigation of Entamoeba gingivalis and Trichomonas tenax in a group of patients with periodontal disease]

The oral cavity is suitable for invasion of many microorganisms. Entamoeba gingivalis (E.gingivalis) and Trichomonas tenax (T.tenax) settle in the oral cavity of patients with poor oral hygiene and gingival disease. In the present study, two slide specimens were prepared from the cole region of the teeth of 46 persons for investigation of the parasites. One of the slide specimens was dried in the air while the other one put into fixative and they were stained with trichrome and Giemsa stains. The two staining methods were used for 36 samples and only Giemsa, for 10 samples. E. gingivalis was positive in 7 (19.44%) out of 36 samples stained by the trichrome stain while T. tenax was positive in one (2.17%) out of 46 samples stained by Giemsa stain. Parasitic infections were found to be positive in seven (21.2%) specimen from 33 patients with periodontal disease and in one (7.69%) specimen from 13 healthy controls. Dental policlinics are generally far from parasitology laboratories and microscopical wet mount examination can not be performed. Therefore dentists can send the specimens and have the parasites diagnosed with Giemsa and trichrome staining methods as an alternative to wet mount examination.

[Entamoeba gingivalis infection among college students in Tangshan]

OBJECTIVE

To investigate the prevalence of Entamoeba gingivalis infection in college students in Tangshan, and analyze the relationship between the infection and human behaviors.

METHODS

551 students of grades 1-3 from six colleges in Tangshan received questionnairing, which covered the oral health state, teeth-brushing, xylitol gum-chewing, diet fondness, and smoking. Specimens were taken from the tooth surface of the lesion or fouling materials by using disinfected toothpicks and the smears were observed microscopically to examine Entamoeba gingivalis infection.

RESULTS

The prevalence of Entamoeba gingivalis infection was 28.3% (156/551), 30.4% (55/181) and 24.6% in males and females (91/370) respectively (chi2=2.09, P>0.05). The prevalence in students with or without oral disorders was 41.2% (84/204) and 20.8% (72/347) respectively, with a significant statistical difference (chi2=26.41, P<0.01); it was 22.5% (53/236) and 32.7% (103/315) among students who cleaned their teeth regularly or irregularly (chi2=6.97, P<0.01); it was 18.3% (17/93) and 30.4% (139/458) among those usually with or without chewing xylitol gum (chi2=5.55, P<0.05).

CONCLUSION

Entamoeba gingivalis infection is common in the college students in Tangshan and it has a close relation to the oral hygiene habits and the presence of oral disorders.

[Antigen detection methods in diagnosis of amebiasis, giardiasis and cryptosporidiosis]

Amebiasis is a significant health problem in developing countries. Humans are infected by two morphologically identical species of Entamoeba. Entamoeba histolytica causes amebic colitis and liver abscess, and Entamoeba dispar is noninvasive. Giardia intestinalis infection is seen worldwide and in all age groups. But giardiasis is especially prevalent in countries with poor sanitation and unsafe water, where it's responsible for most cases of childhood diarrhea. Cryptosporidium parvum, a protozoon, is an obligate intracellular parasite which can cause fatal diarrheal disease in immunocompromised individuals. Generally, the diagnosis of human intestinal protozoa depends on microscopic detection. Microscopic detection is inexpensive, but it is very labor-intensive and requires a skilled microscopist. Antigen detection methods (direct fluorescent antibody, enzyme immunoassay, and rapid, dipstick-like tests) can be performed quickly and do not require an experienced and skilled microscopist. Recently, commercially available diagnostic kits for the intestinal parasites E. histolytica, G.intestinalis and Cryptosporidium spp. use the laboratory diagnosis. In this review, we aimed to discuss the diagnosis of these three intestinal parasites using the antigen tests.

Two different chitinase genotypes in a patient with an amebic liver abscess: a case report

The present work deals with the identification of a patient with two liver abscesses containing two different strains of Entamoeba histolytica, as defined by chitinase gene plymorphisms.

First molecular identification of Entamoeba moshkovskii in human stool samples in Tunisia

We report the first intestinal infections in Tunisia with Entamoeba moshkovskii in two healthy adults. Entamoeba moshkovskii cysts were distinguished from those of the morphologically identical parasites Entamoeba histolytica and Entamoeba dispar by specific nested polymerase chain reaction and sequencing.

[Prevalence and polyparasitism of intestinal protozoa and spatial distribution of Entamoeba histolytica, E. dispar and Giardia intestinalis from pupils in the rural zone of Man in Côte d'Ivoire]

Diseases caused by environmental contamination by micro-organisms, including intestinal helminths and protozoa, are prevalent in developing countries. According to some authors, their strong expansion in some zones of these countries is due primarily to favourable climatic conditions, combined with inadequate hygiene measures and cleaning and the generally low socio-economic level. Progress in disease control has resulted from new studies that improve our understanding of the epidemiology of helminthiases and from the availability of simple tools that are inexpensive and effective against these diseases (chemotherapy with albendazole and mebendazole). On the other hand, surprisingly few such studies have looked at intestinal protozoa, although the WHO reports that approximately 480 million individuals throughout the world are infested by amoebiasis caused by the protozoon Entamoeba histolytica and that 40,000-110,000 people die from it each year. Giardiasis, a cosmopolitan parasitosis, is due to another intestinal protozoon called Giardia intestinalis. To help develop a database on these parasites, we conducted a cross-sectional epidemiological survey in the Man region in western Côte d'Ivoire. Its objectives were to determine the prevalence of intestinal protozoa, to evaluate polyparasitism and to assess the spatial distribution of the pathogenic protozoal species, E. histolytica and G. intestinalis. Overall, 4466 stools samples taken from pupils aged 6 to 16 years of age at 57 different schools were analyzed under an optical microscope by the formol-ether stool concentration method, after preservation in sodium acetate-acetic acid-formalin (SAF). The most common protozoa species in this area were Endolimax nanus (83.8%) and E. coli (74.7%). The regional prevalence of G. intestinalis was 17.5% and of E. histolytica/E. dispar 11.3%. Both species were found in each of the 57 schools. The prevalence of E. histolytica/E. dispar exceeded 15% in six schools, and its spatial distribution was highly disparate. On the other hand, three large areas with substantial G. intestinalis transmission were identified. Polyparasitism of intestinal protozoa is very frequent in these areas; 80.2% of pupils carried at least 2 species. This work confirms the presence and breadth of protozoa species in the Man region. Understanding the spatial distribution of the principal areas where pathogenic protozoa species are transmitted may help to develop programmes for disease control that combine chemotherapy and preventive measures.

Investigation of the prevalence of amoebiasis in Izmir province and determination of Entamoeba spp. using PCR and enzyme immunoassay

Amoebiasis is a common and life-threatening disease. The discrimination of the pathogenic Entamoeba histolytica from the non-pathogenic Entamoeba dispar could be done by advanced methods such as enzyme immunoassay (EIA) and PCR. The aim of this study was to investigate the prevalence of amoebiasis in Izmir province, and differentiate the Entamoeba species by PCR and EIA. Stool samples of 2,047 individuals were examined by direct microscopy, formalin ethyl acetate concentration, trichrome staining and culture, and those found to be positive for E. histolytica/dispar by any of these methods were further analyzed by PCR and EIA for species identification. Fifty-nine of 2,047 (2.9%) stool samples were found to be positive for E. histolytica/dispar with microscopy and/or culture. Among these positive samples, E. histolytica was detected in 14 (23.7%) and 5 (8.5%) samples with PCR and antigen-specific ELISA (EIA), respectively. E. dispar was diagnosed in 31 (52.5%) and 52 (88.1%) of 59 samples with species-specific PCR and EIA, respectively. Risk factors related to infection with Entamoeba spp. and other intestinal parasites included living in shanty houses (p < 0.01), a history of recent immigration to Izmir (p < 0.01), having no social security (p < 0.05) and living with a crowded family (p < 0.01). The results demonstrated the significance of amoebiasis as a public health problem among people with low socio-economic status in Izmir province.

[Epidemiologic and molecular study of Entamoeba histolytica and Entamoeba dispar strains in pacients with diarrhea in Cumana, Sucre state, Venezuela]

An epidemiological and molecular study on E. histolytica and E. dispar was carried out in 428 patients with gastrointestinal symptomatology of diarrhea from different health centers in Cumana, Sucre state. The samples were processed through: direct examination with 0.85% physiological saline solution, temporal lugol staining, trichromic staining and the Ritchie method of concentration; a sucrose gradient was used for cyst isolation. The small subunit of the 16S RNA was amplified by nested, multiplex PCR for the molecular detection. The E. histolytica/E. dispar prevalences according to the direct, Ritchie and trichromic staining methods were 20.09, 13.79 and 12.15%, respectively; while prevalences according to PCR for E. histolytica and E. dispar were 6.31% and 4.44%, respectively, also detecting four cases of mixed infection. Sequencing of the amplified fragments of E. histolytica showed 100% homology with the sequences with strains from Merida (Venezuela), USA, Brazil, Mexico and GenBank. The infections by E. histolytica and E. dispar were statistically associated with age but not with sex. The presence of mucus, blood and abdominal pain were only associated to E. histolytica infection. The moderate prevalence of E. histolytica shows the endemic status of this population and warns about the potential problem as a morbidity and mortality in Sucre state. The frequency of E. dispar in this population suggests the existence of an overestimation problem in the diagnosis of amoebiasis with its clinical and epidemiological implications, and shows the poor knowledge about the true prevalences of this protozoan. The PCR allowed for the differential identification of E. histolytica and E. dispar, as well as the presence of mixed infections, making a great tool for epidemiological amoebiasis studies.

Comparison of stool antigen detection kits to PCR for diagnosis of amebiasis

The present study was conducted to compare two stool antigen detection kits with PCR for the diagnosis of Entamoeba histolytica infections by using fecal specimens submitted to the Department of Microbiology at St. Vincent's Hospital, Sydney, and the Institute of Medical and Veterinary Science, Adelaide, Australia. A total of 279 stool samples containing the E complex (E. histolytica, Entamoeba dispar, and Entamoeba moshkovskii) were included in this study. The stool specimens were tested by using two commercially produced enzyme immunoassays (the Entamoeba CELISA PATH and TechLab E. histolytica II kits) to detect antigens of E. histolytica. DNA was extracted from all of the samples with a Qiagen DNA stool mini kit (Qiagen, Hilden, Germany), and a PCR targeting the small-subunit ribosomal DNA was performed on all of the samples. When PCR was used as a reference standard, the CELISA PATH kit showed 28% sensitivity and 100% specificity. The TechLab ELISA (enzyme-linked immunosorbent assay) kit did not prove to be useful in detecting E. histolytica, as it failed to identify any of the E. histolytica samples which were positive by PCR. With the TechLab kit, cross-reactivity was observed for three specimens, one of which was positive for both E. dispar and E. moshkovskii while the other two samples contained E. moshkovskii. Quantitative assessment of the PCR and ELISA results obtained showed that the ELISA kits were 1,000 to 10,000 times less sensitive, and our results show that the CELISA PATH kit and the TechLab ELISA are not useful for the detection of E. histolytica in stool samples from patients in geographical regions where this parasite is not endemic.

Diagnosis of Entamoeba histolytica in symptomatic children, Jeddah City, Saudi Arabia

Amebiasis is one of the most common parasitic infections worldwide. Entamoeba histolytica and Entamoeba dispar are two morphologically indistinguishable human protozoa parasites that are genetically distinct species. Differential diagnosis of E. histolytica (pathogenic) and E. dispar (non-pathogenic) is essential both for treatment decision and public health knowledge. Stool samples from 500 randomly selected children complaining of gastroenteritis were examined microscopically by direct wet smear and subjected to detection of E. histolytica antigen by ELISA using TechLab E. histolytica II test. E. histolytical E. dispar were also identified at molecular level by targeting the 166 bp, and 752 bp sequences of the 18Sr RNA gene of E. histolytica and E. dispar respectively using polymerase chain reaction technique (PCR). The overall prevalence of E. histolytica/dispar by microscopic examination was 30/500 (6%). E. histolytica was positive in 161500 (3.2%) by antigen detection ELISA technique, whereas 10 samples were not detected microscopically. PCR was able to confirm the presence of E. histolytica in 13/16 cases whereas the 3 samples recorded negative were positive by ELISA; even so there was a good agreement k = 0.86 between the two techniques. In conclusion, stool antigen detection test by ELISA is recommended over PCR in detecting and confirming E. histolytica amoebic enteritis.

Long term formalin preserved stool specimens for detection of intestinal parasites from school aged children in Tripoli, Libya

A total of 949 single stool samples were collected from school aged children (5-14 years old) in the city of Tripoli. The samples were preserved in 10% formalin and examined by routine microscopy using normal saline and Lugol's iodine preparations as well as the formol ethyl concentration method after a storage period of twelve months at room temperature. Of 949 samples examined 4.5% were positive. Giardia lamblia and Entamoeba coli were the only protozoan parasites identified with an infection rate of 3.2% & 1.3% respecttively. No helminthes were detected in any of the samples. About 14% of the children had intestinal yeast infection Candida albicans in their stool of which 0.63% was infected with intestinal parasites. No distortion or alteration of morphology was observed particularly in G. lamblia. Preservation in 10% formalin is a very productive means for the accurate identification of protozoan parasites.

Diagnosis of intestinal amoebiasis by using nested polymerase chain reaction-restriction fragment length polymorphism assay

BACKGROUND

Microscopy is unreliable to distinguish the pathogenic Entamoeba histolytica from the nonpathogenic Entamoeba dispar or Entamoeba moshkovskii in stool specimens.

METHODS

Nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was carried out to detect E. histolytica, E. dispar, and E. moshkovskii DNA in stool samples of 202 patients positive for E. histolytica, E. dispar, or E. moshkovskii by microscopy or culture and in 35 controls. The TechLab E. histolytica II enzyme-linked immunosorbent assay (ELISA) was performed to detect Gal/GalNAc lectin in 45 stool samples positive for E. histolytica, E. dispar, or E. moshkovskii by microscopy or culture. Rapid-indirect hemagglutination assay (IHA) was performed to detect serum antiamoebic antibodies in the 85 patients positive for E. histolytica, E. dispar, or E. moshkovskii in their stool specimens and in the 35 controls.

RESULTS

Nested PCR-RFLP was positive in 175 of 202 (86.6%) patient stool samples and was negative in all 35 negative control stool samples. ELISA was positive in 29 of 45 (64.4%) patient stool samples. The IHA test was positive in 19 of 85 (22.4%) patient serum samples and in one (2.8%) of the 35 control serum samples. Nested PCR-RFLP detected E. histolytica DNA in stool specimens of 12 (63.2%) of 19 seropositive patients, and in 31 (47%) of 66 seronegative patients. TechLab E. histolytica II ELISA detected E. histolytica antigen in stool specimens of six (54.5%) of 11 seropositive patients, and in 23 (67.6%) of 34 seronegative patients.

CONCLUSIONS

Nested PCR-RFLP was useful for the specific detection of E. histolytica, E. dispar, and E. moshkovskii in stool samples.

Prevalence of intestinal parasitic infestation in HIV/AIDS patients with diarrhea in Madurai City, South India

The prevalence and pattern of parasitic infestation among 80 HIV/AIDS patients with diarrhea in Madurai, south India, was studied by microscopy. Eighty HIV-negative patients were used as controls. Intestinal parasites were detected in 31 HIV/AIDS patients (38.7%) and in 14 (17.5%) HIV-negative patients, a difference that was statistically significant (P < 0.05). In HIV/AIDS patients with diarrhea, protozoa accounted for the majority of diarrhea cases (Entamoeba spp. 37.5%, Cryptosporidium parvum 28.7%). It is therefore suggested that enteric infections are more common in HIV-infected patients than in HIV-negative persons in south India, and this may be due to differences in immunological profile, susceptibility as well as factors related to sanitation and the environment.

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.

An Entamoeba sp. strain isolated from rhesus monkey is virulent but genetically different from Entamoeba histolytica☆

An Entamoeba sp. strain, P19-061405, was isolated from a rhesus monkey in Nepal and characterized genetically. The strain was initially identified as Entamoeba histolytica using PCR amplification of peroxiredoxin genes. However, sequence analysis of the 18S rRNA gene showed a 0.8% difference when compared to the reference E. histolytica HM-1:IMSS human strain. Differences were also observed in the 5.8S rRNA gene and the internal transcribed spacer (ITS) regions 1 and 2, and analysis of the serine-rich protein gene from the monkey strain showed unique codon usages compared to E. histolytica isolated from humans. The amino acid sequences of two hexokinases and two glucose phosphate isomerases also differed from those of E. histolytica. Isoenzyme analyses of these enzymes in the monkey strain showed different electrophoretic mobility patterns compared with E. histolytica isolates. Analysis of peroxiredoxin genes indicated the presence of at least seven different types of protein, none of which were identical to proteins in E. histolytica. When the trophozoites from the monkey strain were inoculated into the livers of hamsters, formation of amebic abscesses was observed 7 days after the injection. These results demonstrate that the strain is genetically different from E. histolytica and is virulent. Revival of the name Entamoeba nuttalli is proposed for the organism.