A Comparative Analysis of Microscopy, Coproantigen Serology, and Nested Multiplex PCR in the Laboratory Diagnosis of Entamoeba histolytica Infection.

Objectives Amoebiasis is caused by the most common intestinal protozoan parasite Entamoeba histolytica . This parasite causes amoebic colitis, which is manifested by diarrhea, followed by dysentery. The laboratory diagnosis of intestinal amoebiasis in most cases is by microscopic examination of stool samples. Other nonroutine methods include coproantigen enzyme-linked immunosorbent assay (ELISA) from stool samples, serum ELISA for antibodies, stool culture, isoenzyme analysis, and polymerase chain reaction (PCR). The present study aimed to comparatively analyze the different diagnostic modalities used for the detection of E. histolytica from the stool sample of patients with intestinal amoebiasis. Materials and Methods This study was undertaken with 631 patients, during a period of 3 years, from January 2017 to December 2019. Stool specimen obtained from each patient was subjected to direct microscopic wet mount examination, coproantigen ELISA, and nested multiplex PCR, respectively. Results Out of all the patients tested, 5.2% were positive for E. histolytica. Among the positive cases, stool microscopy was positive in 3.17%, coproantigen ELISA was positive in 29 (4.6%) cases, and PCR was positive in 30 (4.75%) cases. Statistical Analysis The prevalence of E. histolytica infection was summarized as percentages. The three diagnostic tests done were statistically analyzed, taking microscopy as the gold standard. The agreement between techniques (microscopy, coproantigen ELISA, and PCR) was analyzed with kappa statistics. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were summarized as percentage with 95% confidence interval. Conclusion In all suspected amoebiasis cases, a combination of stool microscopy, coproantigen testing with molecular detection of the parasite offers the best approach to diagnosis of this parasitic infection.

[Epidemiological characteristics of amoebic dysentery in China, 2015-2018].

Objective: To understand the characteristics and changes of the incidence of amoebic dysentery in China during 2015-2018, explore the causes of high incidence in some areas and provide a data base for the development of national prevention and control strategies and measures. Methods: Data were collected from the infectious disease reporting management information system from Chinese Disease Control and Prevention. To understand the seasonal, population and area distributions of amoebic dysentery, descriptive epidemiological method and software SPSS 16.0 were used to analyze the amoebic dysentery data. Results: A total of 4 366 amoebic dysentery cases were reported without death in China during 2015-2018. The reported average annual incidence was 0.08/100 000, and the overall proportion of laboratory confirmed cases was 68.23%(2 979/4 366). Amoeba dysentery mainly occurred during May to October. One seasonal peak was observed in 2015 and 2017 (July and June, respectively), and two seasonal peaks were observed in 2016 and 2018 (June and October). The patients were mainly children aged under 5 years (42.28%, 1 846/4 366), and the incidence rate decreased with age in children aged under 10 years. Of these, children under 1 years of age had the highest incidence rate (1.28/100 000). The number of cumulative reported cases in Guangxi, Henan, Guangdong, Heilongjiang and Jiangxi provinces ranked top five from 2015-2018, accounting for 64.50% (2 816/4 366) of the total. The cumulative cases in Dongxing county, Guangxi, in Suixian county, Henan and in Ranghulu district, Heilongjiang, respectively accounted for more than 50.00% of the total number of cases in their provinces. Conclusions: The incidence rate of amoebic dysentery reported in China during 2015-2018 showed a decreasing trend, with a higher incidence in children under 5 years old and a higher number of cases in some areas. It is suggested to further investigate and analyze the diagnosis and reporting of amoeba dysentery in key areas and promote the update of the diagnostic standards for amoeba dysentery.

Intestinal amoebiasis: 160 years of its first detection and still remains as a health problem in developing countries.

Amoebiasis is a parasitic disease caused by Entamoeba histolytica (E. histolytica), an extracellular enteric protozoan. This infection mainly affects people from developing countries with limited hygiene conditions, where it is endemic. Infective cysts are transmitted by the fecal-oral route, excysting in the terminal ileum and producing invasive trophozoites (amoebae). E. histolytica mainly lives in the large intestine without causing symptoms; however, possibly as a result of so far unknown signals, the amoebae invade the mucosa and epithelium causing intestinal amoebiasis. E. histolytica possesses different mechanisms of pathogenicity for the adherence to the intestinal epithelium and for degrading extracellular matrix proteins, producing tissue lesions that progress to abscesses and a host acute inflammatory response. Much information has been obtained regarding the virulence factors, metabolism, mechanisms of pathogenicity, and the host immune response against this parasite; in addition, alternative treatments to metronidazole are continually emerging. An accesible and low-cost diagnostic method that can distinguish E. histolytica from the most nonpathogenic amoebae and an effective vaccine are necessary for protecting against amoebiasis. However, research about the disease and its prevention has been a challenge due to the relationship between E. histolytica and the host during the distinct stages of the disease is multifaceted. In this review, we analyze the interaction between the parasite, the human host, and the colon microbiota or pathogenic microorganisms, which together give rise to intestinal amoebiasis.

Stress-induced nuclear depletion of Entamoeba histolytica 3'-5' exoribonuclease EhRrp6 and its role in growth and erythrophagocytosis.

The 3'-5' exoribonuclease Rrp6 is a key enzyme in RNA homeostasis involved in processing and degradation of many stable RNA precursors, aberrant transcripts, and noncoding RNAs. We previously have shown that in the protozoan parasite Entamoeba histolytica, the 5'-external transcribed spacer fragment of pre-rRNA accumulates under serum starvation-induced growth stress. This fragment is a known target of degradation by Rrp6. Here, we computationally and biochemically characterized EhRrp6 and found that it contains the catalytically important EXO and HRDC domains and exhibits exoribonuclease activity with both unstructured and structured RNA substrates, which required the conserved DEDD-Y catalytic-site residues. It lacked the N-terminal PMC2NT domain for binding of the cofactor Rrp47, but could functionally complement the growth defect of a yeast rrp6 mutant. Of note, no Rrp47 homologue was detected in E. histolytica Immunolocalization studies revealed that EhRrp6 is present both in the nucleus and cytosol of normal E. histolytica cells. However, growth stress induced its complete loss from the nuclei, reversed by proteasome inhibitors. EhRrp6-depleted E. histolytica cells were severely growth restricted, and EhRrp6 overexpression protected the cells against stress, suggesting that EhRrp6 functions as a stress sensor. Importantly EhRrp6 depletion reduced erythrophagocytosis, an important virulence determinant of E. histolytica This reduction was due to a specific decrease in transcript levels of some phagocytosis-related genes (Ehcabp3 and Ehrho1), whereas expression of other genes (Ehcabp1, Ehcabp6, Ehc2pk, and Eharp2/3) was unaffected. This is the first report of the role of Rrp6 in cell growth and stress responses in a protozoan parasite.

Structure of uridine diphosphate N-acetylglucosamine pyrophosphorylase from Entamoeba histolytica.

Uridine diphosphate N-acetylglucosamine pyrophosphorylase (UAP) catalyzes the final step in the synthesis of UDP-GlcNAc, which is involved in cell-wall biogenesis in plants and fungi and in protein glycosylation. Small-molecule inhibitors have been developed against UAP from Trypanosoma brucei that target an allosteric pocket to provide selectivity over the human enzyme. A 1.8 Å resolution crystal structure was determined of UAP from Entamoeba histolytica, an anaerobic parasitic protozoan that causes amoebic dysentery. Although E. histolytica UAP exhibits the same three-domain global architecture as other UAPs, it appears to lack three α-helices at the N-terminus and contains two amino acids in the allosteric pocket that make it appear more like the enzyme from the human host than that from the other parasite T. brucei. Thus, allosteric inhibitors of T. brucei UAP are unlikely to target Entamoeba UAPs.

Colocutaneous fistula secondary to amoebiasis.

Here we present an interesting and extremely rare case of a 66 year old male who developed a colocutaneous fistula secondary to amoebiasis. The patient presented with an acute history of right lower abdominal pain, weight loss and a palpable mass. A CT scan demonstrated a fluid filled cavity in the right iliac fossa consistent with an appendiceal abscess which was drained under radiological guidance. However, following drainage his symptoms remained requiring open surgical drainage, and a controlled caecostomy was performed due to a small caecal perforation. Despite appropriate conservative therapy he failed to progress, and developed localised sepsis in the right iliac fossa with a colocutaneous fistula, requiring a formal right hemicolectomy. The histological examination confirmed the presence of abundant trophozoites of Entamoeba histolytica.We highlight the fact that in the modern age of immigration and long distance travel, it will become increasingly likely that the so-called 'tropical' diseases will present throughout the world. This case also highlights the need to keep an open mind in cases that do not progress as expected, and to react accordingly to any unusual developments.