Amebic infection in humans

Intestinal protozoa infections and associated factors among diarrheal under-five children in Borena district, central Ethiopia

In impoverished nations, intestinal protozoan infections (IPIs) are a leading cause of diarrhea in children. However, in the majority of afflicted nations, including Ethiopia, the role played by each intestinal protozoa species in causing diarrhea and the risk factors linked with it are not adequately addressed. This would support focused intervention efforts. The prevalence of IPIs and related variables were evaluated between April and May 2023 among 380 under-five children in Borena district of Amhara region, central Ethiopia, by an institution-based cross-sectional survey. Systematic random sampling was used to select study participants. The study included a structured questionnaire to gather data regarding sociodemographic characteristics and perceived risk factors for IPIs. Using saline and iodine wet mounts as well as Richie's modified formol-ethyl acetate concentration technique, stool samples were collected and analyzed under a microscope. SPSS was used to enter and evaluate the data. At a 95 % confidence level, bivariate and multivariate logistic regressions were used to determine the factors linked to intestinal protozoa infection. Among 380 participants, 136 (35.8 %) were tested positive for one or more intestinal parasite species at least by one of the diagnostic methods. 118 (31.1 %; 95 % CI: 26.6-36.1) children were infected by intestinal protozoans. The parasites detected were: G. lamblia 71 (18.7 %) and E. histolytica/disar 54 (14.2 %), E. vermicularis 3 (0.8 %), A. lumbricoides 2 (0.5 %), H. nana 2 (0.5 %) and T. trichiura 1 (0.3 %). Seven (1.8 %) participants were infected by both protozoan species. Children whose mothers/guardians did not attend formal education were at higher risk of IPI (adjusted odds ratio (AOR) = 2.801; 95 %CI: 1.666-4.711, p < 0.001) than children from literate mothers/guardians. Absence of functional toiltet in the household (AOR = 1.952; 95 %CI: 1.195-3.187, p = 0.008), hand washing with water alone, rather than with soap/ash (AOR = 3.052; 95 %CI: 1.203-7.746, p = 0.019) and having frequent contact with animals (AOR = 2.103; 95 %CI: 1.238-3.574, p = 0.006) were associated with IPIs. These findings revealed that Giardia lamblia and Entamoeba histolytica are public health problems causing diarrhea among under-five children in the study area, and their transmission is associated with the illiteracy of mothers/guardians, the absence of functional toilets, not using soap/ash during hand washing, and frequent contact with domestic animals. Therefore, when diagnosing, treating, and educating patients about diarrhea, healthcare professionals should take these protozoans into account.

An atypical cause of right lower abdominal pain: amoebiasis, a family cluster

In this case report we present a family cluster of amoebiasis in a nonendemic region. A 46-year-old women, diagnosed with Crohn's disease for which she received no maintenance therapy, was evaluated for the suspicion of a flare. At colonoscopy however, atypical findings for Crohn's disease were seen. Histopathologic examination revealed micro-organisms compatible with amoebiasis. Interestingly, 4 years before this event she started a new relationship with a 38-year-old man who was diagnosed with liver-amoebiasis 3 months after the start of their relationship. On top of this, her 18-year-old daughter was diagnosed with amoebiasis 2 years after her diagnosis. The source of the infection remains unknown, but we speculate that the infection was transmitted feco-orally between the different members of this family. These cases illustrate that we should be aware of parasitological causes of colitis, especially in patients with atypical endoscopic images or when a close "relative" is diagnosed with amoebiasis.

An encapsulated bulky abdominal abscess due to amoeba

We report a rare case of amebiasis associated with an intraabdominal abscess without colitis, an intestinal perforation, or other extraintestinal amebiasis. A patient was admitted with cirrhosis and a history of spontaneous bacterial peritonitis (SBP) and was found to have a high C-reactive protein (CRP) level. Dynamic CT and ultrasound echo findings showed an intraabdominal abscess. No intestinal lesions or extraintestinal lesions other than the intraabdominal abscess were observed. Blood cultures and puncture fluid cultures were negative for bacteria. However, microscopic examination of the puncture fluid showed a cystic form of amoeba, leading to a diagnosis of an amoeba abscess. The abscess disappeared after 10 days of oral treatment with metronidazole. When an abdominal abscess is seen in an immunocompromised patient such as a cirrhotic patient, amoeba infection should be considered as a possible diagnosis.

Drug Repurposing Approach against Novel Coronavirus Disease (COVID-19) through Virtual Screening Targeting SARS-CoV-2 Main Protease

Novel coronavirus disease (COVID-19) was identified from China in December 2019 and spread rapidly through human-to-human transmission, affecting so many people worldwide. Until now, there has been no specific treatment against the disease and repurposing of the drug. Our investigation aimed to screen potential inhibitors against coronavirus for the repurposing of drugs. Our study analyzed sequence comparison among SARS-CoV, SARS-CoV-2, and MERS-CoV to determine the identity matrix using discovery studio. SARS-CoV-2 Mpro was targeted to generate an E-pharmacophore hypothesis to screen drugs from the DrugBank database having similar features. Promising drugs were used for docking-based virtual screening at several precisions. Best hits from virtual screening were subjected to MM/GBSA analysis to evaluate binding free energy, followed by the analysis of binding interactions. Furthermore, the molecular dynamics simulation approaches were carried out to assess the docked complex's conformational stability. A total of 33 drug classes were found from virtual screening based on their docking scores. Among them, seven potential drugs with several anticancer, antibiotic, and immunometabolic categories were screened and showed promising MM/GBSA scores. During interaction analysis, these drugs exhibited different types of hydrogen and hydrophobic interactions with amino acid residue. Besides, 17 experimental drugs selected from virtual screening might be crucial for drug discovery against COVID-19. The RMSD, RMSF, SASA, Rg, and MM/PBSA descriptors from molecular dynamics simulation confirmed the complex's firm nature. Seven promising drugs for repurposing against SARS-CoV-2 main protease (Mpro), namely sapanisertib, ornidazole, napabucasin, lenalidomide, daniquidone, indoximod, and salicylamide, could be vital for the treatment of COVID-19. However, extensive in vivo and in vitro studies are required to evaluate the mentioned drug's activity.

Entamoeba histolytica and amoebic liver abscess in northern Sri Lanka: a public health problem

Entamoeba histolytica (E. histolytica) is a facultative protozoan parasite implicated in amoebic liver abscesses (ALA), the most common extraintestinal manifestation of this infection. E. histolytica is endemic to sub-tropical and tropical countries and has been a major public health concern in northern Sri Lanka (SLK) for the last three decades. This has been attributed to a multitude of factors such as poor sanitation, hygiene, male sex, middle age, overcrowding, unsanitary practices in the production of indigenous alcoholic beverages, and alcohol consumption. Additionally, while rates of E. histolytica have declined substantially throughout the rest of the island, largely due to better infrastructure, it remains pervasive in the northern peninsula, which is generally less developed. Infection arises primarily from fecal-oral transmission through the consumption of contaminated drinking water containing cysts. Upon ingestion, cysts multiply into trophozoites and colonize the host colonic mucosa using lectin and cysteine proteases as virulence factors, leading to host invasion. Symptoms occur along a spectrum, from asymptomatology, to pyrexia, abdominal cramping, and amoebic dysentery. Colonization of the colon results in the formation of distinct flask-shaped ulcers along the epithelium, and eventual penetration of the lamina propria via the production of matrix metalloproteinases. ALA then develops through trophozoite migration via the mesenteric hepatic portal circulation, where microabscesses coalesce to form a single, large right-lobe abscess, commonly on the posterior aspect. The progression of infection to invasive disease is contingent on the unique interplay between host and pathogen factors, such as the strength of host-immunity to overcome infection and inherent pathogenicity of the Entamoeba species. As a preventable illness, E. histolytica complications such as ALA impose a significant burden on the healthcare system. This mini-review highlights epidemiological trends, risk factors, diagnostic modalities, treatment approaches, and opportunities for prevention of E. histolytica-induced ALA, to help address this endemic problem on the island of SLK.

Acute fulminant necrotizing amebic colitis in a pediatric patient: a rare complication of amebiasis with high mortality-a case report

Background

The majority of amebic infections among humans remain asymptomatic. Rarely, the disease takes a fulminant acute course due to the development of necrotizing amebic colitis. This complication is usually found in adult patients. However, on the contrary, this case was diagnosed in a 9-year-old patient. He was transferred to the Sirimavo Bandaranayake Specialized Children’s Hospital (SBSCH), Peradeniya from the District General Hospital, Kilinochchi. To our knowledge, this is the first report of this rare complication in a child in Sri Lanka.

Case presentation

We present a case of acute fulminant necrotizing amebic colitis in a 9-year-old boy. Surgical exploration revealed extensive ulceration and multiple perforations in the entire colon. PAS-Martius Yellow 40 stain highlighted amebae with erythrophagocytosis within the necrotic debris of the ulcers. The polymerase chain reaction (PCR) that was conducted to confirm the diagnosis was positive for Entameba histolytica. The post-operative course was marked with antimicrobial treatment for septicemia and the need for ventilator assistance. Antimicrobial treatment included intravenous metronidazole. The patient progressively recovered and was discharged on a normal diet.

Conclusion

This case reports an acute fulminant necrotizing amebic colitis in a 9-year-old patient. After the treatments, the patient progressively recovered and was discharged on a normal diet. E. histolytica infections in northern Sri Lanka should be given attention as a public health concern. Furthermore, this case highlights that acute fulminant amebic colitis requires early surgical intervention, aggressive supportive and anti-amebic treatments. Clinicians should be cognizant of this potentially fatal complication of amebic colitis.

Antiamoebic drugs for treating amoebic colitis

BACKGROUND

Infection with the protozoan Entamoeba histolytica is common in low- and middle-income countries, and up to 100,000 people with severe disease die every year. Adequate therapy for amoebic colitis is necessary to reduce illness, prevent development of complicated disease and extraintestinal spread, and decrease transmission.

OBJECTIVES

To evaluate antiamoebic drugs for treating amoebic colitis.

SEARCH METHODS

We searched the available literature up to 22 March 2018. We searched the Cochrane Infectious Diseases Group Specialised Register, CENTRAL, MEDLINE, Embase, LILACS, mRCT, and conference proceedings. We contacted individual researchers, organizations, and pharmaceutical companies, and we checked reference lists.

SELECTION CRITERIA

Randomized controlled trials of antiamoebic drugs given alone or in combination, compared with placebo or another antiamoebic drug, for treating adults and children with a diagnosis of amoebic colitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility and methodological quality of trials and extracted and analysed the data. We calculated clinical and parasitological failure rates and rates of relapse and adverse events as risk ratios (RRs) with 95% confidence intervals (CIs), using a random-effects model. We determined statistical heterogeneity and explored possible sources of heterogeneity using subgroup analyses. We carried out sensitivity analysis by using trial quality to assess the robustness of reported results.

MAIN RESULTS

In total, 41 trials (4999 participants) met the inclusion criteria of this review. In this update, we added four trials to the 37 trials included in the first published review version. Thirty trials were published over 20 years ago. Only one trial used adequate methods of randomization and allocation concealment, was blinded, and analysed all randomized participants. Only one trial used an E histolytica stool antigen test, and two trials used amoebic culture.Tinidazole may be more effective than metronidazole for reducing clinical failure (RR 0.28, 95% CI 0.15 to 0.51; 477 participants, eight trials; low-certainty evidence) and is probably associated with fewer adverse events (RR 0.65, 95% CI 0.46 to 0.92; 477 participants, 8 trials; moderate-certainty evidence). Compared with metronidazole, combination therapy may result in fewer parasitological failures (RR 0.36, 95% CI 0.15 to 0.86; 720 participants, 3 trials; low-certainty evidence), but we are uncertain which combination is more effective than another. Evidence is insufficient to allow conclusions regarding the efficacy of other antiamoebic drugs.

AUTHORS' CONCLUSIONS

Compared with metronidazole, tinidazole may be more effective in reducing clinical failure and may be associated with fewer adverse events. Combination drug therapy may be more effective for reducing parasitological failure compared with metronidazole alone. However, these results are based mostly on small trials conducted over 20 years ago with a variety of poorly defined outcomes. Tests that detect E histolytica more accurately are needed, particularly in countries where concomitant infection with other bacteria and parasites is common.

Nontravel-related invasive Entamoeba histolytica infection with probable heterosexual transmission

Introduction

In industrialized countries, amebiasis usually occurs in migrants and travelers returning from areas where the disease is endemic, primarily by ingestion of contaminated food or water. Person-to-person transmission can occur, mainly by fecal-oral contact, but sexual transmission has also been described [1,[3], [4], [5]].

Presentation of case

We report a man with Entamoeba histolytica colitis and a large liver abscess (16.5 × 14 cm) in Portugal, who had no relevant travel history and whose only risk factor was his heterosexual partner. The abscess required drainage of 1950 mL of “chocolate-milk” purulent fluid, with rapid symptomatic improvement. The diagnosis was established by real-time reverse transcription PCR for Entamoeba histolytica in the liver aspirate, with positive IgG antibodies. He received a total of 16 days of ceftriaxone and metronidazole followed by 7 days of paromomycin.

Conclusion

As enteric infections may be sexually transmitted, in industrialized countries, even in the absence of travel, sexual history should not be neglected.

Antioxidant defense of Nrf2vspro-inflammatory system of NF-κB during the amoebic liver infection in hamster

Entamoeba histolyticais the causative agent of amoebic liver abscess (ALA), which course with an uncontrolled inflammation and nitro-oxidative stresses, although it is well known that amoeba has an effective defence mechanisms against this toxic environment, the underlying molecular factors responsible for progression of tissue damage remain largely unknown. The purpose of the present study was to determine during the acute stage of ALA in hamsters, the involvement of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and nuclear factor-kappa B (NF-κB), which are activated in response to oxidative stress. From 12 h post-infection the ALA was visible, haematoxylin-eosin and Masson's trichrome stains were consistent with these observations, and alanine aminotransferase, alkaline phosphatase and γ-glutamyl transpeptidase serum activities were increased too. At 48 h after infection, liver glycogen content was significantly reduced. Western blot analyses showed that 4-Hydroxy-2-nonenal peaked at 12 h, while glycogen synthase kinase-3β, cleaved caspase-3, pNF-κB, interleukin-1β and tumour necrosis factor-α were overexpressed from 12 to 48 h post-infection. Otherwise, Nrf2 and superoxide dismutase-1, decreased at 48 h and catalase declined at 36 and 48 h. Furthermore, heme oxygenase-1 was increased at 12 and 24 h and decreased to normal levels at 36 and 48 h. These findings suggest for the first time that the host antioxidant system of Nrf2 is influenced during ALA.

X-ray structures of thioredoxin and thioredoxin reductase from Entamoeba histolytica and prevailing hypothesis of the mechanism of Auranofin action

The anti-arthritic gold-containing drug Auranofin is lethal to the protozoan intestinal parasite Entamoeba histolytica, the causative agent of human amebiasis, in both culture and animal models of the disease. A putative mechanism of Auranofin action proposes that monovalent gold, Au(I), released from the drug, can bind to the redox-active dithiol group of thioredoxin reductase (TrxR). Au(I) binding in the active site is expected to prevent electron transfer to the downstream substrate thioredoxin (Trx), thus interfering with redox homeostasis in the parasite. To clarify the molecular mechanism of Auranofin action in more detail, we determined a series of atomic resolution X-ray structures for E. histolytica thioredoxin (EhTrx) and thioredoxin reductase (EhTrxR), the latter with and without Auranofin. Only the disulfide-bonded form of the active site dithiol (Cys(140)-Cys(143)) was invariably observed in crystals of EhTrxR in spite of the addition of reductants in various crystallization trials, and no gold was found associated with these cysteines. Non-catalytic Cys(286) was identified as the only site of modification, but further mutagenesis studies using the C286Q mutant demonstrated that this site was not responsible for inhibition of EhTrxR by Auranofin. Interestingly, we obtained both of the catalytically-relevant conformations of this bacterial-like, low molecular weight TrxR in crystals without requiring an engineered disulfide linkage between Cys mutants of TrxR and Trx (as was originally done with Escherichia coli TrxR and Trx). We note that the -CXXC- catalytic motif, even if reduced, would likely not provide space sufficient to bind Au(I) by both cysteines of the dithiol group.

The Amoebicidal Effect of Ergosterol Peroxide Isolated from Pleurotus ostreatus

Dysentery is an inflammation of the intestine caused by the protozoan parasite Entamoeba histolytica and is a recurrent health problem affecting millions of people worldwide. Because of the magnitude of this disease, finding novel strategies for treatment that does not affect human cells is necessary. Ergosterol peroxide is a sterol particularly known as a major cytotoxic agent with a wide spectrum of biological activities produced by edible and medicinal mushrooms. The aim of this report is to evaluate the amoebicidal activity of ergosterol peroxide (5α, 8α-epidioxy-22E-ergosta-6,22-dien-3β-ol isolated from 5α, 8α-epidioxy-22E-ergosta-6,22-dien-3β-ol) (Jacq.) P. Kumm. f. sp. Florida. Our results show that ergosterol peroxide produced a strong cytotoxic effect against amoebic growth. The inhibitory concentration IC50 of ergosterol peroxide was evaluated. The interaction between E. histolytica and ergosterol peroxide in vitro resulted in strong amoebicidal activity (IC50  = 4.23 nM) that may be due to the oxidatory effect on the parasitic membrane. We also tested selective toxicity of ergosterol peroxide using a cell line CCL-241, a human epithelial cell line isolated from normal human fetal intestinal tissue. To the best of our knowledge, this is the first report on the cytotoxicity of ergosterol peroxide against E. histolytica, which uncovers a new biological property of the lipidic compound isolated from Pleurotus ostreatus (Jacq.) P. Kumm. f. sp. Florida.

Prevalent HLA Class II Alleles in Mexico City Appear to Confer Resistance to the Development of Amebic Liver Abscess

Amebiasis is an endemic disease and a public health problem throughout Mexico, although the incidence rates of amebic liver abscess (ALA) vary among the geographic regions of the country. Notably, incidence rates are high in the northwestern states (especially Sonora with a rate of 12.57/100,000 inhabitants) compared with the central region (Mexico City with a rate of 0.69/100,000 inhabitants). These data may be related to host genetic factors that are partially responsible for resistance or susceptibility. Therefore, we studied the association of the HLA-DRB1 and HLA-DQB1 alleles with resistance or susceptibility to ALA in two Mexican populations, one each from Mexico City and Sonora. Ninety ALA patients were clinically diagnosed by serology and sonography. Genomic DNA was extracted from peripheral blood mononuclear cells. To establish the genetic identity of both populations, 15 short tandem repeats (STRs) were analyzed with multiplexed PCR, and the allelic frequencies of HLA were studied by PCR-SSO using LUMINEX technology. The allele frequencies obtained were compared to an ethnically matched healthy control group (146 individuals). We observed that both affected populations differed genetically from the control group. We also found interesting trends in the population from Mexico City. HLA-DQB1*02 allele frequencies were higher in ALA patients compared to the control group (0.127 vs 0.047; p= 0.01; pc= NS; OR= 2.9, 95% CI= 1.09-8.3). The less frequent alleles in ALA patients were HLA-DRB1*08 (0.118 vs 0.238 in controls; p= 0.01; pc= NS; OR= 0.42, 95% CI= 0.19-0.87) and HLA-DQB1*04 (0.109 vs 0.214; p= 0.02; pc= NS; OR= 0.40, 95% CI= 0.20-0.94). The haplotype HLA-DRB1*08/-DQB1*04 also demonstrated a protective trend against the development of this disease (0.081 vs. 0.178; p=0.02; pc=NS; OR= 0.40, 95% CI= 0.16-0.93). These trends suggest that the prevalent alleles in the population of Mexico City may be associated with protection against the development of ALA.

Seroepidemiology of Entamoeba histolytica Infection in General Population in Rural Durango, Mexico

Background

The seroepidemiology of Entamoeba histolytica in Mexico has been scantily studied. The aim of the study was to determine the seroprevalence and correlates of E. histolytica antibodies in adults in rural areas in Durango, Mexico.

Methods

Through a cross-sectional study, E. histolytica IgG antibodies were determined in 282 adults living in rural Durango, Mexico using an enzyme-linked immunoassay. In addition, seroprevalence association with the socio-demographic, housing conditions, and behavioral characteristics of the subjects studied was investigated.

Results

One hundred and eighteen (41.8%) of the 282 rural subjects had anti-E. histolytica IgG antibodies. Multivariate analysis showed that E. histolytica exposure was positively associated with source of drinking water (OR = 2.73; 95% CI: 1.33 - 5.58; P = 0.005), and poor education of the head of the family (OR = 1.53; 95% CI: 1.03 - 2.27; P = 0.03). In contrast, E. histolytica exposure was negatively associated with consumption of unpasteurized cow milk (OR = 0.55; 95% CI: 0.31 - 0.96; P = 0.03), and crowding at home (OR = 0.33; 95% CI: 0.17 - 0.64; P = 0.0009).

Conclusions

The seroprevalence of E. histolytica infection found in adults in rural Durango is high compared with those reported in other Mexican populations. The correlates of E. histolytica seropositivity found in the present study may be useful for the planning of optimal preventive measures against E. histolytica infection.

Clinical consequences of new diagnostic tools for intestinal parasites

Following the success of nucleic acid-based detection in virology and bacteriology, multiplex real-time PCRs are increasingly used as first-line diagnostics in clinical parasitology, replacing microscopy. The detection and quantification of parasite-specific DNA in faeces is highly sensitive and specific and allows for cost-effective high-throughput screening. In this paper we discuss the clinical consequences of this radical change in diagnostic approach, as well as its potential drawbacks. In the Netherlands, routine diagnostic laboratories have been pioneering the implementation of multiplex real-time PCR for the detection of pathogenic intestinal protozoa and this has resulted in increased detection rates of Giardia lamblia and Cryptosporidium spp. As a consequence of this new diagnostic approach, expertise in the field of parasite morphology by conventional light microscopy seems to be disappearing in most of the high-throughput microbiological laboratories. As a result, to maintain a high standard of care, a formalized exchange of critical information between clinicians and laboratory staff is necessary to determine the most appropriate testing either in local laboratories or in reference centres, based on clinical signs and symptoms, exposure and immune status. If such a diagnostic algorithm is lacking, important infections in travellers, immigrants and immunocompromised patients may be missed.

Cystic hepatic lesions: a review and an algorithmic approach

OBJECTIVE

The purpose of this article is to review the different cystic hepatic lesions, with an emphasis on the imaging features that help to differentiate them, and to propose a practical algorithm for approaching the diagnosis of these lesions.

CONCLUSION

The number and morphology of the lesions and determination of whether there is a solid component are key imaging features that are helpful for approaching the diagnosis of cystic hepatic lesions. Familiarity with these features and knowledge of the clinical associations will help the radiologist to establish a definitive diagnosis or provide a reasonable differential diagnosis.

Structure-based identification of inositol polyphosphate 1-phosphatase from Entamoeba histolytica

Inositol polyphosphate 1-phosphatase from Entamoeba histolytica (EhIPPase) is an Mg(2+)-dependent and Li(+)-sensitive enzyme that catalyzes the hydrolysis of inositol 1,4-bisphosphate [Ins(1,4)P2] into myo-inositol 1-monophosphate and PO4(3-). In the present work, EhIPPase has been biochemically identified and its crystal structure has been determined in the presence of Mg(2+) and PO4(3-) at 2.5 Å resolution. This enzyme was previously classified as a 3'(2'),5'-bisphosphate nucleotidase in the NCBI, but its biochemical activity and structural analysis suggest that this enzyme behaves more like an inositol polyphosphate 1-phosphatase. The ability of EhIPPase to hydrolyze the smaller Ins(1,4)P2 better than the bulkier 3'-phosphoadenosine 5'-phosphate (PAP) is explained on the basis of the orientations of amino-acid residues in the binding site. This structure is the first of its class to be determined from any protozoan parasite, and is the third to determined among all organisms, following its rat and bovine homologues. The three-dimensional fold of EhIPPase is similar to those of other members of the inositol monophosphatase superfamily, which also includes inositol monophosphatase, 3'(2'),5'-bisphosphate nucleotidase and fructose-1,6-bisphosphate 1-phosphatase. They all share conserved residues essential for metal binding and substrate hydrolysis, with the motif D-Xn-EE-Xn-DP(I/L)DG(S/T)-Xn-WD-Xn-GG. The structure is divided into two domains, namely α+β and α/β, and the substrate and metal ions bind between them. However, the ability of each enzyme class to act specifically on its cognate substrate is governed by the class-specific amino-acid residues at the active site.

[Drug therapy of infectious diarrhea. Part 2: Chronic diarrhea]

Diarrheal diseases are among the most common diseases worldwide. In this review the current treatment recommendations for acute (Part 1) and chronic (Part 2) infectious diarrhea are summarized and typical enteropathogens are discussed. The second part of the article describes chronic diarrhea, its related pathogens and treatment. In contrast to acute diarrhea which is mainly caused by viral and typical bacterial pathogens, chronic diarrhea has mainly non-infectious origins. Protozoal pathogens, such as Giardia lamblia and Entamoeba histolytica in particular are found and more rarely bacterial pathogens, such as Tropheryma whipplei. Opportunistic pathogens cause diarrhea in immunocompromised patients, such as in HIV patients. In these patients cytomegalovirus (CMV) colitis or infections with Cryptosporidium spp., Cyclospora cayetanensis, Isospora belli or microsporidia have to be considered. Besides targeted specific antimicrobial therapy, anti-retroviral drugs improving the underlying immunosuppression and thus the reconstitution of the adaptive immune response remain a cornerstone of the treatment in HIV-positive patients.

Liver masses: a clinical, radiologic, and pathologic perspective

Liver masses present a relatively common clinical dilemma, particularly with the increasing use of various imaging modalities in the diagnosis of abdominal and other symptoms. The accurate and reliable determination of the nature of the liver mass is critical, not only to reassure individuals with benign lesions but also, and perhaps more importantly, to ensure that malignant lesions are diagnosed correctly. This avoids the devastating consequences of missed diagnosis and the delayed treatment of malignancy or the unnecessary treatment of benign lesions. With appropriate interpretation of the clinical history and physical examination, and the judicious use of laboratory and imaging studies, the majority of liver masses can be characterized noninvasively. Accurate characterization of liver masses by cross-sectional imaging is particularly dependent on an understanding of the unique phasic vascular perfusion of the liver and the characteristic behaviors of different lesions during multiphasic contrast imaging. When noninvasive characterization is indeterminate, a liver biopsy may be necessary for definitive diagnosis. Standard histologic examination usually is complemented by immunohistochemical analysis of protein biomarkers. Accurate diagnosis allows the appropriate selection of optimal management, which is frequently reassurance or intermittent follow-up evaluations for benign masses. For malignant lesions or those at risk of malignant transformation, management depends on the tumor staging, the functional status of the uninvolved liver, and technical surgical considerations. Unresectable metastatic masses require oncologic consultation and therapy. The efficient characterization and management of liver masses therefore requires a multidisciplinary collaboration between the gastroenterologist/hepatologist, radiologist, pathologist, hepatobiliary or transplant surgeon, and medical oncologist.

Misdiagnosed amoebic colitis leading to severe dysentery and necrotizing colitis--report of a case and review of the literature

We present a case of amoebic colitis, misdiagnosed as inflammatory bowel disease and treated with corticosteroids, leading to severe necrotizing enterocolitis. We review the literature on the epidemiology, pathogenesis, diagnosis, and treatment of amoebic dysentery, with special emphasis on the association between immunosuppressive treatment and the development of severe invasive amoebiasis.

Invasive amoebiasis: a review of Entamoeba infections highlighted with case reports

Entamoeba histolytica infections of the gastrointestinal tract are common in the developing world but rare in North America. The authors present two cases: one involving an individual who had not travelled to an endemic area and another involving an individual who was born in Bulgaria. Both presented with severe abdominal pain and diarrhea. Endoscopic assessment revealed scattered colonic ulcerations and one patient was found to have a liver abscess on imaging. Stool ova and parasite studies were negative in both cases and both were diagnosed on review of colonic biopsies. On review of all Entamoeba cases in the Calgary Health Zone (Alberta), ova and parasite analysis found an average of 63.7 Entamoeba cases per year and a pathology database review revealed a total of seven cases of invasive E histolytica (2001 to 2011). Both patients responded well to antibiotic therapy. E histolytica should be considered in new-onset colitis, especially in individuals from endemic areas.

Unusual multiple large abscesses of the liver: interest of the radiological features and the real-time PCR to distinguish between bacterial and amebic etiologies

We report a rare case of amebiasis generating 19 large liver abscesses. Such a quantity of abscesses is rare, especially when occurring in a young casual traveler without any immunodeficiency disorders. A possible co-infection was excluded. By contrast, the amebic etiology was confirmed by means of serology and real-time PCR.