Histolytica Infection Research Articles

Epidemiological features of intestinal infection with Entamoeba histolytica in Taiwan, 2002–2010

Amebiasis remains an important public health problem worldwide, and immigration and an increase in international travel have affected the incident cases of the disease. The purpose of this study was to assess the prevalence of Entamoeba histolytica in Taiwan between 2002 and 2010. We analyzed data from surveillance programs run by the Centers for Disease Control, Taiwan (Taiwan CDC), and only laboratory-confirmed cases were analyzed. In total, 1796 cases with E. histolytica infections were included in our analysis. Among them, 788 (44%) of the cases were imported, and 1008 (56%) were locally acquired. The average annual incidence rate of E. histolytica infections was 0.49 and 9.26 per 100,000 for local patients and immigrants/foreign workers from endemic countries, respectively. The annual incidence of E. histolytica infections among immigrants/foreign workers was significantly higher than among Taiwanese who had not traveled abroad (P < 0.0001). Travelers to E. histolytica-endemic areas (e.g., Southeast countries) had a higher risk acquiring an E. histolytica infection. This study emphasized that E. histolytica infection is an important intestinal infectious disease in Taiwan. The risk of infection with E. histolytica for travelers was higher for those with destinations in South and Southeast Asia. To control E. histolytica infections in Taiwan, a sensitive surveillance system needs to be established, and the amebiasis-screening program for immigrants/foreign workers from endemic countries should be enforced.

English

Amebic liver abscess (ALA) is the most frequent extraintestinal manifestation of Entamoeba histolytica infection. It is largely a disease of tropical and developing countries and is also a common problem in India. Approximately 80% of the abscesses are solitary, 83% of these are located in the right lobe and 17% are located in the left lobe of the liver. Pleuropulmonary complications of ALA are reported in 20% of cases and rupture into peritoneal cavity occurs in 6-9% of patients. Rupture into the peritoneal cavity more often occurs with left-sided abscesses. We present a case of simultaneous rupture of amebic abscess of both liver lobes (intraperitoneal) which as per our knowledge has not yet been reported.

Laboratory diagnosis of amebiasis in a sample of students from southeastern Brazil and a comparison of microscopy with enzyme-linked immunosorbent assay for screening of infections with Entamoeba sp.

Epidemiological studies on amebiasis have been reassessed since Entamoeba histolytica and E. dispar were first recognized as distinct species. Because the morphological similarity of these species renders microscopic diagnosis unreliable, additional tools are required to discriminate between Entamoeba species. The objectives of our study were to compare microscopy with ELISA kit (IVD®) results, to diagnose E. histolytica infection, and to determine the prevalence of amebiasis in a sample of students from southeastern Brazil. In this study, diagnosis was based on microscopy due to its capacity for revealing potential cysts/trophozoites and on two commercial kits for antigen detection in stool samples. For 1,403 samples collected from students aged 6 to 14 years who were living in Divinópolis, Minas Gerais, Brazil, microscopy underestimated the number of individuals infected with E. histolytica/E. dispar (5.7% prevalence) compared with the ELISA kit (IVD®)-based diagnoses (15.7% for E. histolytica/E. dispar). A comparison of the ELISA (IVD®) and light microscopy results returned a 20% sensitivity, 97% specificity, low positive predictive value, and high negative predictive value for microscopy. An ELISA kit (TechLab®) that was specific for E. histolytica detected a 3.1% (43/1403) prevalence for E. histolytica infection. The ELISA kit (IVD®) can be used as an alternative screening tool. The high prevalence of E. histolytica infection detected in this study warrants the implementation of actions directed toward health promotion and preventive measures.

Microscopy versus enzyme linked immunosorbent assay test for detection of Entamoeba histolytica infection in stool samples.

Microscopy versus enzyme linked immunosorbent assay test for detection of Entamoeba histolytica infection in stool samples.

A Retrospective Analysis of the Results of a Five-Year (2005-2009) Parasitological Examination for Common Intestinal Parasites from Bale-Robe Health Center, Robe Town, Southeastern Ethiopia.

A cross-sectional retrospective survey using the past five years clinical records (2005–2009) was conducted. The study was aimed at assessing the status of common intestinal parasites from Bale-Robe Health Center, Southeastern Ethiopia, in 2009/2010. The survey involved collection of data recorded on intestinal parasite from the health center during 2005–2009. Precoded questionnaires and interviews were also supplemented for knowledge attitude practices survey (KAPs survey) to assess awareness level of treatment seekers. Analysis of the various associations and strength of significant variations among qualitative and quantitative variables were assessed. The results revealed that Entamoeba histolytica (36.1%) and Giardia lamblia (11.0%), both being protozoan parasites were found to be the most prevalent intestinal parasites encountered during 2005–2009. The least prevalent intestinal parasite recorded was Strongyloides stercoralis (1.1%). Most intestinal parasites were detected among age group of 15 years and above than 0–4 and 5–14 years as shown in Table 4. There was a significant correlation between intestinal parasites prevalence and the age of treatment seeking individuals (P < 0.05). A sharp increasing trend of E. histolytica and Ascaris lumbricoides infections was observed owing to low personal and environmental sanitation of the majority of the society. Initiation of health education at different levels could be recommended to mitigate infectious parasites in the area.

Natural Infection of Baboons by Entamoeba Histolytica Elicits Anti-Gal Lectin Heavy Subunit Iga and Igg Antibodies with Shared Epitope Specificity to That of Humans

Non-human primates, such as baboons (Papio hamadryas anubis), are natural hosts for Entamoeba species; infections can be asymptomatic or result in invasive lethal disease. It was sought to determine whether following natural infection by Entamoeba. histolytica, baboon anti-amebic antibodies recognized native Gallectin, a recombinant portion of the lectin heavy subunit (designated LC3) and specific heavy subunit epitopes; we compared the specificity of anti-amebic antibodies from baboons to that of humans following asymptomatic E. histolytica infection or cure of amebic liver abscess (ALA). Female baboons (n=54), aged one to three years of age and living in captivity were screened for infection by real time PCR. E. histolytica infection was found in 37 baboons and was associated with serum anti-LC3 IgG (73%) and anti-LC3 IgA (46%) or intestinal anti-Gal-Lectin IgA antibody responses (49%), p<0.021 for each compared to that observed with baboons having an E. dispar infection (n=10) or uninfected baboons (n=7). The ELISA OD reading for anti-LC3 or anti-lectin antibodies correlated strongly with the presence of a PCR CT value indicative of E. histolytica infection. In humans with asymptomatic E. histolytica infection or those recently cured of ALA, 63% and 57% had serum anti- LC3 IgA and 65% and 57% had serum anti-LC3 IgG antibodies respectively. Epitope- specific synthetic peptides were used as capture antigens in ELISA; for baboons that possessed anti-LC3 and anti-lectin antibodies, 74% had anti-peptide IgG or IgA antibodies, compared to 86% of asymptomatic humans and 92% of ALA subjects(P>0.05).

DETECTION OF HUMAN INTESTINAL PROTOZOA BY USING MULTIPLEX ALLELE SPECIFIC POLYMERASE CHAIN REACTION (MAS-PCR) In New Damietta City

Enteric protozoa continue to be the most commonly encountered parasitic diseases causing significant morbidity and mortality in developing regions of the world affecting millions of people. This study assessed the use of Multiplex Allele Specific Polymerase Chain Reaction (MAS-PCR) assay and microscopy for detection and identification of common pathogenic protozoan parasites in New Damietta city of North Delta region, Egypt. During Jun 2013 until Sept 2013, fresh stool samples were obtained from 249 patients up to 65 years of age attending the internal clinic of the Damietta University Hospital and those visiting their general practitioner (GP) of outpatient clinics because of gastrointestinal symptoms. Stool samples collected was preserved at -200C for DNA extraction whilst the remaining was preserved in sodium acetate-acetic acid formalin and concentrated using the formol-ether technique for microscopic examination. DNA extracts were analyzed with the multiplex allele specific Polymerase Chain Reaction (MAS-PCR) for pathogenic protozoan parasites. The diagnostic results obtained using a multiplex allele specific PCR for the detection of E. histolytica/dispar, G. lamblia and C. parvum/C. hominis were compared with these obtained by routine microscopy of faecal samples from patients. 69 samples were positive by MAS-PCR assays, 9 cases of G. intestinalis infection, 34 cases of D. fragilis infection, 3 cases of E. histolytica infection, 17 cases E.dispar and 6 cases of Cryptosporidium infection in the clinical samples. By microscopy, only 32 samples were positive for one or more of the enteric protozoa, 5cases of G. intestinalis infection, 9cases of D. fragilis infection, 13 cases of E. histolytica infection, and 1 cases of Cryptosporidium infection in the clinical samples. However, there are no cases of E.dispar observed. Mixed infections were detected in 4 samples. The sensitivities varied from 58% for D. fragilis to 47% for E. histolytica, 35% for Giardia, and 30% for Cryptosporidium, while the specificities also varied from 97% for E. histolytica to 99% for D. fragilis and 100% for E.dispar . No cross-reactivity was detected in stools samples containing various bacterial, viral, and other protozoan species. This present study showed relatively high rates of protozoa infections in the study patients. The study has also demonstrated that the multiplex real time PCR assay was more sensitive compared to microscopy in the diagnosis of the intestinal protozoa parasites and thus, molecular methods must be considered the diagnostic methods of choice for enteric protozoan parasites. Keywords: Human intestinal protozoa, Stools specimens, Microscopy, Multiplex Allele Specific Polymerase Chain Reaction (MAS-PCR), Diagnosis.

The Cell Surface Proteome of Entamoeba histolytica

Surface molecules are of major importance for host-parasite interactions. During Entamoeba histolytica infections, these interactions are predicted to be of prime importance for tissue invasion, induction of colitis and liver abscess formation. To date, however, little is known about the molecules involved in these processes, with only about 20 proteins or protein families found exposed on the E. histolytica surface. We have therefore analyzed the complete surface proteome of E. histolytica. Using cell surface biotinylation and mass spectrometry, 693 putative surface-associated proteins were identified. In silico analysis predicted that ∼26% of these proteins are membrane-associated, as they contain transmembrane domains and/or signal sequences, as well as sites of palmitoylation, myristoylation, or prenylation. An additional 25% of the identified proteins likely represent nonclassical secreted proteins. Surprisingly, no membrane-association sites could be predicted for the remaining 49% of the identified proteins. To verify surface localization, 23 proteins were randomly selected and analyzed by immunofluorescence microscopy. Of these 23 proteins, 20 (87%) showed definite surface localization. These findings indicate that a far greater number of E. histolytica proteins than previously supposed are surface-associated, a phenomenon that may be based on the high membrane turnover of E. histolytica.

Appendicial Entamoeba Histolytica Ulcer Mimicking Cancer

Purpose: A 58-year-old diabetic Lebanese male was evaluated for a screening colonoscopy. He had traveled to Lebanon two years ago, but was otherwise asymptomatic. During the colonoscopy, there was a 12-mm ulcerated lesion at the appendiceal orifice that was suggestive of a neoplasm. However, biopsy of the lesion showed colonic mucosa with cryptitis and mucosal erosions, with adherent amebae organisms. Moreover, ingested red blood cells were seen within the organisms, suggesting the lesion was most likely related to an Entamoeba histolytica infection. The patient was treated with Flagyl 500 mg tid and Paromomycin 250 mg tid times both for 10 days. He will have a repeat colonoscopy in a couple of months to evaluate if the ulcer healed. Entamoeba histolytica is an intestinal protozoan that is responsible for 40,000 deaths worldwide. It commonly infects people who live in underdeveloped countries, or individuals who travel to endemic areas. Roughly 90% of Entamoeba histolytica infections are asymptomatic, but the other 10% may have symptoms that can be quite profound, ranging from mild diarrhea to severe dysentery. Invasive infections, which are rare and occur in 0.5% of cases, include fulminant colitis with bowel necrosis, perforation, toxic megacolon, and spread to the liver, lungs, brain, and heart. The diagnosis and treatment is crucial, even in asymptomatic individuals like our patient, since it can quickly progress to invasive disease, especially in those who are diabetics, immunocompromised, alcoholics, or have the Entamoeba histolytica strain. It is best diagnosed by a combination of serology or antigen testing in conjunction with detection of the parasite in the stool. However, direct visualization of the colonic mucosa by colonoscopic biopsy can be of tremendous help, since these serological markers stay positive even if the infection has cleared in asymptomatic individuals. Classic findings on colononscopy and biopsy include diffuse, multiple areas of punctuate ulcerations that show non-specific inflammation or, as in severe disease, may appear necrotic. However, it is extremely rare to have focal, solitary ulcers present in asymptomatic patients who have Entamoeba histolytica strain infections, as these ulcers can be mistaken for a neoplasm. Our case demonstrates a diabetic, asymptomatic 58-year-old Lebanese male with such a case. Solitary Entamoeba histolytica-induced colonic ulcers, albeit rare, must be considered in any patient with a focal colonic ulcer or mass that mimics colonic neoplasm. Biopsy of the ulcer and histologic evaluation must be undertaken with prompt treatment with Flagyl and/or Parmomomycin, so as to prevent invasive Entamoeba histolytica infection and its complications.

Infection-induced anaemia: a cross-sectional study of 14,636 German travellers aged 20–49 years

Anaemia is a frequently diagnosed condition which can develop as a consequence of numerous factors, including infectious diseases (IDs). Travelling, especially in sub-/tropical regions, leads to an elevated risk of contracting IDs. The aim of our study was to assess the epidemiological significance of IDs in inducing anaemia among a large cohort of returned travellers. This was a cross-sectional study in which data on 17,009 returned travellers aged 20-49years who consulted the travel medicine clinic of the University of Munich between 1999 and 2011 were retrieved and analysed. Of the returned travellers, 8.3% (6.0% of males/10.4% of females) were diagnosed with anaemia. The prevalence of anaemia was significantly elevated among patients of African (21.4/28.3%) and Asian (11.6/15.7%) origin. When the study population was restricted to the 14,636 travellers of German origin, 7.1% of the returned travellers (4.6/9.6%) were diagnosed with anaemia. The prevalence was significantly elevated among patients who travelled for >30days (5.7 of males/10.6% of females) and for male travellers visiting friends and relatives (7.7%). However, these correlations were confounded by malaria. The prevalence of anaemia was significantly elevated only among returned travellers diagnosed with malaria (36.1 of males/26.9% of females) and with symptomatic intestinal Entamoeba histolytica infections (30.0/33.3%). Following the exclusion of confounding by malaria from the statistical analysis, the prevalence of anaemia was found to be significantly elevated among patients of African and Asian origin, and among patients of German origin who had travelled for >30days, it could be mainly attributable to chronic, long-lasting causes. Although more than 550 travel-associated IDs were assessed in our study, only symptomatic intestinal Entamoeba histolytica infections and, to an even larger extent, malaria were determined to be of epidemiological significance for inducing anaemia among travellers.

Immunogenicity and protective efficacy of heparan sulphate binding proteins of Entamoeba histolytica in a guinea pig model of intestinal amoebiasis

Entamoeba histolytica infection is associated with considerable morbidity and mortality in the form of intestinal and extraintestinal amoebiasis. No vaccine is yet available for amoebiasis. Heparan Sulphate Binding Proteins (HSBPs) from E. histolytica were evaluated for immunogenicity and protective efficacy in a Guinea pig model. Animals were immunized subcutaneously with 30μg of HSBP by three weekly inoculations. The immunogenicity of HSBP was determined by antibody response (IgG, IgM and IgA), splenocyte proliferation assay and in vitro direct amoebicidal assay with splenic lymphocytes and monocytes from vaccinated and control animals. The efficacy of the vaccine was evaluated by challenge infection to vaccinated and control animals by intra-caecal inoculation of E. histolytica trophozoites and comparing gross and histopathological findings in caeca of these animals. HSBP was found to induce specific anti-amoebic response as seen by specific antibody production and direct amoebicidal activity of splenocytes. The vaccine also showed partial protection against challenge infection in vaccinated animals as shown by mild/absent lesions and histopathological findings.

DETECTION AND DIFFERENTIATION OF HUMAN PROTOZOAN PARASITES IN STOOL SPECIMENS BY USING MULTIPLEX ALLELE SPECIFIC POLYMERASE CHAIN REACTION (MAS-PCR) In New Damietta City, Egypt

Enteric protozoa continue to be the most commonly encountered parasitic diseases causing significant morbidity and mortality in developing regions of the world affecting millions of people. This study assessed the use of Multiplex Allele Specific Polymerase Chain Reaction (MAS-PCR) assay and microscopy for detection and identification of common pathogenic protozoan parasites in New Damietta city of North Delta region, Egypt. Between Jun 2013 until Sept 2013, fresh stool samples were obtained from 249 patients up to 65 years of age attending the internal clinic of the Damietta University Hospital and those visiting their general practitioner (GP) of outpatient clinics because of gastrointestinal symptoms. Stool samples collected was preserved at -200C for DNA extraction whilst the remaining was preserved in sodium acetate-acetic acid formalin and concentrated using the formol-ether technique for microscopic examination. DNA extracts were analyzed with the multiplex allele specific Polymerase Chain Reaction (MAS-PCR) for pathogenic protozoan parasites. The diagnostic results obtained using a multiplex allele specific PCR for the detection of E. histolytica/dispar, G. lamblia and C. parvum/C. hominis were compared with these obtained by routine microscopy of faecal samples from patients. 69 samples were positive by MAS-PCR assays , 9 cases of G. intestinalis infection, 34 cases of D. fragilis infection, 3 cases of E. histolytica infection, 17 cases E.dispar and 6 cases of Cryptosporidium infection in the clinical samples. By microscopy, only 32 samples were positive for one or more of the enteric protozoa, 5cases of G. intestinalis infection, 9cases of D. fragilis infection, 13 cases of E. histolytica infection, and 1 cases of Cryptosporidium infection in the clinical samples. However, there are no cases of E.dispar observed. Mixed infections were detected in 4 samples. The sensitivities varied from 58% for D. fragilis to 47% for E. histolytica, 35% for Giardia, and 30% for Cryptosporidium, while the specificities also varied from 97% for E. histolytica to 99% for D. fragilis and 100% for E.dispar . No cross-reactivity was detected in stool samples containing various other bacterial, viral, and protozoan species. This present study showed relatively high rates of protozoa infections in the study patients. The study has also demonstrated that the multiplex real time PCR assay was more sensitive compared to microscopy in the diagnosis of the intestinal protozoa parasites and thus, molecular methods must be considered the diagnostic methods of choice for enteric protozoan parasites. Keywords: Human intestinal protozoa, Stool specimens, Microscopy, Multiplex Allele Specific Polymerase Chain Reaction (MAS-PCR), Diagnosis.

Genomic distribution of SINEs in Entamoeba histolytica strains: implication for genotyping.

BackgroundThe major clinical manifestations of Entamoeba histolytica infection include amebic colitis and liver abscess. However the majority of infections remain asymptomatic. Earlier reports have shown that some E. histolytica isolates are more virulent than others, suggesting that virulence may be linked to genotype. Here we have looked at the genomic distribution of the retrotransposable short interspersed nuclear elements EhSINE1 and EhSINE2. Due to their mobile nature, some EhSINE copies may occupy different genomic locations among isolates of E. histolytica possibly affecting adjacent gene expression; this variability in location can be exploited to differentiate strains.ResultsWe have looked for EhSINE1- and EhSINE2-occupied loci in the genome sequence of Entamoeba histolytica HM-1:IMSS and searched for homologous loci in other strains to determine the insertion status of these elements. A total of 393 EhSINE1 and 119 EhSINE2 loci were analyzed in the available sequenced strains (Rahman, DS4-868, HM1:CA, KU48, KU50, KU27 and MS96-3382. Seventeen loci (13 EhSINE1 and 4 EhSINE2) were identified where a EhSINE1/EhSINE2 sequence was missing from the corresponding locus of other strains. Most of these loci were unoccupied in more than one strain. Some of the loci were analyzed experimentally for SINE occupancy using DNA from strain Rahman. These data helped to correctly assemble the nucleotide sequence at three loci in Rahman. SINE occupancy was also checked at these three loci in 7 other axenically cultivated E. histolytica strains and 16 clinical isolates. Each locus gave a single, specific amplicon with the primer sets used, making this a suitable method for strain typing. Based on presence/absence of SINE and amplification with locus-specific primers, the 23 strains could be divided into eleven genotypes. The results obtained by our method correlated with the data from other typing methods. We also report a bioinformatic analysis of EhSINE2 copies.ConclusionsOur results reveal several loci with extensive polymorphism of SINE occupancy among different strains of E. histolytica and prove the principle that the genomic distribution of SINEs is a valid method for typing of E. histolytica strains.

High occurrence of Entamoeba histolytica in the municipalities of Ariquemes and Monte Negro, State of Rondônia, Western Amazonia, Brazil

Entamoeba histolytica infections were investigated in residents of the Ariquemes and Monte Negro municipalities in Rondônia State, Brazil. Stool samples of 216 individuals were processed by the spontaneous sedimentation method and analyzed by microscopy for detection of the E. histolytica/E. dispar complex, followed by the immunoassay method using an enzyme-linked immunosorbent assay-based kit for the E. histolytica stool antigen. E. histolytica/E. dispar cysts were present in 61% (50/82) and 44% (59/134) of the samples from Ariquemes and Monte Negro respectively, with a significant difference in the occurrence of infection between the two populations [p < 0.05; χ2 = 5.2; odds ratio = 2.0 (1.1 - 3.6)]. The E. histolytica antigen detection rate was 36.6% (30/82) for stool samples from Ariquemes, and 19.4% (26/134) for stool taken from the residents of Monte Negro. The rate of the occurrence of amoebiasis was significantly higher in the population from Ariquemes [p < 0.05; χ2 = 7.8; odds ratio = 2.4 (1.2 - 4.7)]. Due to the high occurrence of E. histolytica infected residents diagnosed in the region and the unavailability in local clinics of a test to distinguish between the two Entamoeba species, physicians should consider treating E. histolytica/E.dispar infections. The results indicate that E. histolytica infection is highly endemic in the studied areas.

Sialic acid-dependent attachment of mucins from three mouse strains to Entamoeba histolytica

Mouse strain-specific differences in the carbohydrate composition of intestinal mucins were hypothesized to account for strain-dependent susceptibility to Entamoeba histolytica. To test this hypothesis, intestinal mucins from susceptible and resistant inbred strains of mice were analyzed for their O-glycan content and for their ability to inhibit amoebic adherence to (GalNAc)12–27-HSA neo-glycoproteins. The results showed that the colorectal mucin O-glycan of susceptible CBA mice was lower in sialic acid content than that of resistant C57BL/6 and BALB/c mice. Mucins from CBA mice were more potent inhibitors of E. histolytica adherence to neo-glycoproteins than were mucins from C57BL/6 or BALB/c mice. Consistent with the role of terminal Gal/GalNAc as a receptor for amoebic adherence, sialidase treatment of C57BL/6 and BALB/c colorectal mucins increased their ability to inhibit E. histolytica adherence to the neo-glycoproteins. These results provide evidence of mouse strain-specific differences in the sialic acids content of mucin O-glycans. These dissimilarities likely contribute to the differential susceptibility of the three mouse strains to E. histolytica infection.

Seroprevalence of Entamoeba histolytica Infection among Chinese Men Who Have Sex with Men

BackgroundMen who have sex with men (MSM) were found to be one of the high-risk populations for Entamoeba histolytica (E. histolytica) infection. Accompanied by the prevalence of human immunodeficiency virus (HIV) among MSM, invasive amebiasis caused by E. histolytica has been paid attention to as an opportunistic parasitic infection. However, the status of E. histolytica infection among MSM has been barely studied in mainland China.MethodsSeroprevalance of E. histolytica was determined using an enzyme-linked immunosorbent assay based on a cross-sectional study conducted in Beijing and Tianjin, China. Factors potentially associated with E. histolytica infection were identified by logistic regression analysis.ResultsA total of 602 MSM were included in the study and the laboratory data on serostatus of E. histolytica were available for 599 of them (99.5%). 246 (41.1%) and 51 (8.5%) of the study participants were E. histolytica seropositive and HIV seropositive, respectively. Univariate analyses suggested preferred anal sex behaviors were associated with E. histolytica seropositivity. In multivariate logistic regression analysis, “only has receptive anal sex” (OR: 2.03; 95% CI: 1.22 3.37), “majority receptive anal sex” (OR: 1.83; 95% CI: 1.13, 2.95), and “sadomasochistic behavior (SM)” (OR: 2.30; 95% CI: 1.04, 5.13) were found to be significantly associated with E. histolytica infection.ConclusionsHigh seroprevalence of E. histolytica infection was observed among MSM from Beijing and Tianjin, China. Receptive anal sex behavior and SM were identified as potential predictors. Therefore, E. histolytica and HIV co-infection needs to be concerned among MSM due to their sharing the common risk behaviors.

Different Clinical Outcomes of Entamoeba histolytica in Malaysia: Does Genetic Diversity Exist?

The present study was conducted to investigate the clinical outcomes of Entamoeba histolytica infection in symptomatic and asymptomatic Orang Asli (aborigine) communities in Malaysia. Examination was performed on 500 stool samples obtained from Orang Asli communities in 3 different states using formalin-ether concentration, trichrome staining, and single-round PCR techniques. Out of 500 stool samples, single infection of E. histolytica, Entamoeba dispar, and Entamoeba moshkovskii was identified in 3.2%, 13.4%, and 1%, respectively. In addition, 10 samples had mixed infections with E. histolytica and E. dispar. Six samples containing E. dispar were also positive for E. moshkovskii, and only 2 samples had E. histolytica in association with E. dispar and E. moshkovskii. Seventeen E. histolytica-positive samples were from symptomatic subjects, whereas the remaining 11 samples came from asymptomatic subjects. These findings suggest a predominant distribution of pathogenic potential of E. histolytica strains in this community. Therefore, further studies on genotyping of E. histolytica is required, to find out association between E. histolytica genotype and the outcome of the infection.

Entamoeba histolytica or Entamoeba histolytica/E. dispar

In Vol.5, No.2, 2012, Jundishapur Journal of Microbiology a paper entitled “A study on prevalence of gastrointestinal parasitic infections in HIV (+) patients referred to Ahvaz Razi Hospital in 2008-2009” was published. We are grateful to Dr Yosefi et al. for his effective paper in this journal. We read this manuscript with a great interest but there is point that should be taken into consideration. In the paper it has been claimed that of HIV positive patient 1.7% was infected with Entamoeba histolytica cyst (1). We would like to discuss on this topic. It is now known that the parasite previously named as E. histolytica actually consists of two morphologically identical but genetically distinct species, E. histolytica, which is the causative organism of invasive intestinal and extra-intestinal amoebiasis. The other is E. dispar, a non-pathogenic intestinal commensally protozoan organism (2). Differential diagnosis of E. histolytica and E. dispar in stool samples is not easy on the basis of microscopy alone, except for the case of hematophagous trophozoites in acute dysentery. Currently, some expensive methods such as amoebic antigen and DNA detection, isoenzyme electerophoretic pattern, PCR-basis methods, are available to differentiate both nonpathogenic E. dispar from pathogenic E. histolytica, especially in cyst passer person (3, 4). An expert consultation of WHO on amoebiasis in Mexico City stressed needs for improved methods for the specific diagnosis of E. histolytica infections based on technologies appropriate for use in developing world (5). Also, This meeting recommended that when diagnosis is made by light microscopy, the cysts of two species are indistinguishable and should be reported as E. histolytica / E. dispar. Because in this paper differential diagnosis was not done on this cases and diagnosis was done with routine microscopy method, it is better than as other recent studies in Iran, this change to one of HIV positive patient 1.7% was infected with E. histolytica /E.dispar cyst.

Prevalence and genetic diversity of Entamoeba species infecting macaques in southwest China

Many colonies of macaques (Macaca fascicularis and Macaca mulatta) are maintained in China, especially in Guangxi and Guizhou. A total of 803 fresh stool samples infected with Entamoeba were obtained from three big colonies of macaques located in southwest China. The samples were examined for the presence of five Entamoeba species using PCR. Entamoeba nuttalli, Entamoeba dispar, Entamoeba coli, and Entamoeba chattoni infections were detected, but Entamoeba histolytica infection was not. This study is the first to report on the prevalence of E. nuttalli in wild macaques from China. Eighteen E. nuttalli isolates and five E. dispar isolates were obtained by culturing the samples in Tanabe-Chiba medium. The serine-rich protein (SRP), ribosomal RNA (rRNA), hexokinase (HXK), glucose-6-phosphate isomerase (GPI), and phosphoglucomutase (PGM) genes of E. nuttalli isolates were compared with other reported isolates. The results showed clear differences among the Chinese E. nuttalli isolates and other isolates based on the SRP gene sequences. However, HXK, GPI, and PGM genes of these strains were similar to those of other isolates. The rRNA genes of E. coli and E. chattoni were also amplified and analyzed from these samples. The results suggested that host species might be a more important factor than geographic location in amebic genetic diversity.

TNFα-Mediated Liver Destruction by Kupffer Cells and Ly6Chi Monocytes during Entamoeba histolytica Infection

Amebic liver abscess (ALA) is a focal destruction of liver tissue due to infection by the protozoan parasite Entamoeba histolytica (E. histolytica). Host tissue damage is attributed mainly to parasite pathogenicity factors, but massive early accumulation of mononuclear cells, including neutrophils, inflammatory monocytes and macrophages, at the site of infection raises the question of whether these cells also contribute to tissue damage. Using highly selective depletion strategies and cell-specific knockout mice, the relative contribution of innate immune cell populations to liver destruction during amebic infection was investigated. Neutrophils were not required for amebic infection nor did they appear to be substantially involved in tissue damage. In contrast, Kupffer cells and inflammatory monocytes contributed substantially to liver destruction during ALA, and tissue damage was mediated primarily by TNFα. These data indicate that besides direct antiparasitic drugs, modulating innate immune responses may potentially be beneficial in limiting ALA pathogenesis.