AMEBIASIS AND “NONPATHOGENIC” INTESTINAL PROTOZOA

Surgical Emergencies in the ICU

Surgical emergencies are common in the critical care setting and require prompt diagnosis and management. Here, we discuss some of the surgical emergencies involving the gastrointestinal, hepatobiliary, and genitourinary sites. In addition, foreign body aspiration and necrotizing soft-tissue infections have been elaborated. Clinicians should be aware of the risk factors, keys examination findings, diagnostic modalities, and medical as well as surgical treatment options for these potentially fatal illnesses.

Multi-Laboratory Evaluation of a Lateral Flow Rapid Test for Detection of Amebic Liver Abscess

Independent evaluations of XEh Rapid^®, an IgG4-based rapid dipstick test, were performed to assess its diagnostic performance to detect amebic liver abscess (ALA) using 405 samples at seven laboratories in four countries. The test showed high diagnostic specificity (97-100%) when tested with samples from healthy individuals (n = 100) and patients with other diseases (n = 151). The diagnostic sensitivity was tested with a total of 154 samples, and the results were variable. It was high in three laboratories (89-94%), and moderate (72%) and low (38%) in two other laboratories. Challenges and issues faced in the evaluation process are discussed. Nevertheless, XEh Rapid is promising to be developed into a point-of-care test in particular for resource-limited settings, and thus merits further confirmation of its diagnostic sensitivity.

Entamoeba histolytica DNA Detection in Serum from Patients with Suspected Amoebic Liver Abscess

Amoebic liver abscess (ALA) is regularly seen in travelers or immigrants from tropical countries. The diagnosis relies on liver imaging that is not specific and on the detection of anti-Entamoeba histolytica antibodies, which cannot distinguish an acute from a former infection. We tested whether E. histolytica DNA detection in serum can improve the diagnosis of ALA. We retrospectively tested available serum samples taken from patients with ALA and non-ALA space-occupying lesions of the liver between 1 January 2010 and 30 November 2019. The quantitative PCR (qPCR) assay tested specifically amplifies a 99-bp fragment of the small-subunit rRNA gene of E. histolytica We analyzed 76 samples (19 ALA and 57 non-ALA samples) collected from 76 patients within 6 days before and after the antiamoebic treatment. Serum qPCR results were positive for 17 of 19 ALA patients and for none of the control patients (sensitivity and specificity were 89.5% and 100%, respectively). In parallel, the sensitivity and specificity of anti-E. histolytica antibody detection were 100% and 89.5%, respectively. The two false-negative qPCR results may be explained by ongoing metronidazole treatment or a possible persistent seropositivity that was not caused by the current liver abscess. Additionally, of 12 abscess pus aspirates (5 from ALA and 7 from non-ALA samples) tested, 5 were qPCR positive and 7 were qPCR negative, with concordant results in serum. This study demonstrates that cell-free circulating E. histolytica DNA can be detected in serum in ALA. This may assist in both positive diagnoses and treatment efficacy follow-up. The origin of this circulating DNA remains to be investigated.

First case of amebic liver abscess 22 years after the first occurrence

A 72-year-old man consulted in November 2012 for abdominal pain in the right upper quadrant. The patient had a history of suspected hepatic amebiasis treated in Senegal in 1985 and has not traveled to endemic areas since 1990. Abdominal CT scan revealed a liver abscess. At first, no parasitological tests were performed and the patient was treated with broad-spectrum antibiotics. Only after failure of this therapy, serology and PCR performed after liver abscess puncture established the diagnosis of hepatic amebiasis. The patient was treated with metronidazole and tiliquinol-tilbroquinol. Amebic liver abscess is the most frequent extra-intestinal manifestation. Hepatic amebiasis 22 years after the last visit to an endemic area is exceptional and raises questions on the mechanisms of latency and recurrence of these intestinal protozoan parasites.

An uncommon case of hepatopulmonary amoebiasis

Amoebiasis is an uncommon infection in developed countries caused by the protozoan Entamoeba histolytica. Amoebic liver abscess is the most frequent extraintestinal presentation of the disease; pleuropulmonary involvement is rare, occurring mostly by rupture of the abscess into the pleural space or lung parenchyma. We describe a case of a 48-year-old migrant from São Tomé e Príncipe, with fever, wasting, dry cough and right upper abdominal pain for the past 2 months. The CT scan revealed a voluminous liver abscess with thrombosis of the right suprahepatic and inferior vena cava, right pulmonary lobar abscess and multiple diffuse condensations in both lungs. Aspirated pus resembled anchovy sauce; blood and aspirated material cultures for infectious agents were negative. Serology for E. histolytica was positive, and the diagnosis of hepatopulmonary amoebiasis with infectious phlebitis was confirmed by positive PCR in the liver pus. Treatment with metronidazole+paramomycin led to clinical and radiological resolution.

Parasitic infections in solid organ transplant recipients

Parasitic infections are an uncommon but potentially severe complication in solid organ transplant (SOT) recipients. An increase in donors who have emigrated from tropical areas and more transplant recipients traveling to endemic areas have led to a rise in parasitic infections reported among SOT recipients. Clinicians should include these infections in their differential diagnosis and promote adherence to preventive measures in SOT recipients.

[Two cases of pulmonary amebiasis]

CASE 1: A 74-year-old man having a week's fever and diagnosed with a liver abscess was treated with several antibiotics and percutaneous liver drainage. His respiration gradually worsened and chest computed tomography (CT) showed right pleural effusion and a left-lung mass. Percutaneous fine needle aspiration of the pulmonary mass detected Entamoeba histolytica. CASE 2: A 44-year old, zoo office worker admitted for fever and right chest pain was found in CT to have right pleural effusion and a mass with a liver abscess necessitating abscess drainage. Injected contrast medium detected a fistula connected to the right. Following surgical drainage, E. histolytica was detected from the resected lung. Both cases responded well to metronidazole.

Cardiac manifestations of parasitic infections part 1: overview and immunopathogenesis

Parasitic infections produce a wide spectrum of cardiac manifestations. They may involve various anatomic structures of the heart and are manifested clinically as myocarditis, cardiomyopathies, pericarditis, or pulmonary hypertension in many resource-constrained settings. However, many parasitic infections involving the heart may also be currently diagnosed in developed countries due to growing worldwide travel, blood transfusions, and increasing numbers of immunosuppression states such as organ transplantation, use of immunosuppressive agents, or HIV/AIDS. Clinicians anywhere in the globe need to be aware of the potential cardiac manifestations of parasitic diseases. This is part one of a three-part series discussing parasites of the heart. In this section, we provide a general overview and immunopathogenesis of parasitic infections of the heart.

Pyogenic and amebic liver abscesses

Pyogenic and amebic liver abscesses are the two most common hepatic abscesses. Amebic abscesses are more common in areas where Entamoeba histolytica is endemic, whereas pyogenic abscesses are more common in developed countries. Pyogenic abscess severity is dependent on the bacterial source and the underlying condition of the patient. Amebic liver abscess is more prevalent in individuals with suppressed cell-mediated immunity, men, and younger people. The right lobe of the liver is the most likely site of infection in both types of hepatic abscess. Patients usually present with a combination of fever, right-upper-quadrant abdominal pain, and hepatomegaly. Jaundice is more common in the pyogenic abscess. The diagnosis is often delayed and is usually made through a combination of radiologic imaging and microbiologic, serologic, and percutaneous techniques. Treatment involves antibiotics along with percutaneous drainage or surgery.

Amebic liver abscess

Amebic liver abscess is the most common extraintestinal manifestation of infection with Entamoeba histolytica, and it is associated with significant morbidity and mortality. In this article the most recent available information is reviewed relating to epidemiology, pathogenesis, presentation, diagnosis, and treatment. We reviewed thousands of cases of amebic liver abscess in the medical literature and present that information as it pertains to mortality, gender, anatomic location of abscesses, and clinical signs and symptoms.

Emerging from obscurity: biological, clinical, and diagnostic aspects of Dientamoeba fragilis

Ever since its first description in 1918, Dientamoeba fragilis has struggled to gain recognition as a significant pathogen. There is little justification for this neglect, however, since there exists a growing body of case reports from numerous countries around the world that have linked this protozoal parasite to clinical manifestations such as diarrhea, abdominal pain, flatulence, and anorexia. A number of studies have even incriminated D. fragilis as a cause of irritable bowel syndrome, allergic colitis, and diarrhea in human immunodeficiency virus patients. Although D. fragilis is most commonly identified using permanently stained fecal smears, recent advances in culturing techniques are simplifying as well as improving the ability of investigators to detect this organism. However, there are limitations in the use of cultures since they cannot be performed on fecal samples that have been fixed. Significant progress has been made in the biological classification of this organism, which originally was described as an ameba. Analyses of small-subunit rRNA gene sequences have clearly demonstrated its close relationship to Histomonas, and it is now known to be a trichomonad. How the organism is transmitted remains a mystery, although there is some evidence that D. fragilis might be transmitted via the ova of the pinworm, Enterobius vermicularis. Also, it remains to be answered whether the two distinct genotypes of D. fragilis recently identified represent organisms with differing virulence.

Amebic liver abscesses masquerading as pyemic abscesses

We describe a 50-year-old man who presented with multiple liver abscesses that suggested biliary sepsis or portal pyemia. A wet preparation of a sample of aspirate showed the presence of amebic trophozoites, and subsequent serological testing for amebae was strongly reactive.

Amebic liver abscess

Amebiasis is a widespread parasitic disease caused by Entamoeba histolytica. This protozoan organism is the third leading parasitic cause of death in the developing world and is an important health risk to travelers in endemic areas. Amebiasis most commonly results in asymptomatic colonization of the gastrointestinal tract, but some patients may develop intestinal invasive disease or extraintestinal disease-amebic liver abscess being the most common extraintestinal manifestation. This article reviews epidemiologic features, pathophysiology, clinical features, diagnostic tests, imaging studies, treatment of amebic liver abscess, and prevention measures.

Ectonucleotide diphosphohydrolase activities in Entamoeba histolytica

In this work, we describe the ability of living cells of Entamoeba histolytica to hydrolyze extracellular ATP. In these intact parasites, whose viability was determined by motility and by the eosin method, ATP hydrolysis was low in the absence of any divalent metal (78 nmol P(i)/h/10(5) cells). Interestingly, in the presence of 5 mM MgCl(2) an ecto-ATPase activity of 300 nmol P(i)/h/10(5) cells was observed. The addition of MgCl(2) to the extracellular medium increased the ecto-ATPase activity in a dose-dependent manner. At 5 mM ATP, half-maximal stimulation of ATP hydrolysis was obtained with 1.23 mM MgCl(2). Both activities were linear with cell density and with time for at least 1 h. The ecto-ATPase activity was also stimulated by MnCl(2) and CaCl(2) but not by SrCl(2), ZnCl(2), or FeCl(3). In fact, FeCl(3) inhibited both Mg(2+)-dependent and Mg(2+)-independent ecto-ATPase activities. The Mg(2+)-independent ATPase activity was unaffected by pH in the range between 6.4 and 8. 4, in which the cells were viable. However, the Mg(2+)-dependent ATPase activity was enhanced concomitantly with the increase in pH. In order to discard the possibility that the ATP hydrolysis observed was due to phosphatase or 5'-nucleotidase activities, several inhibitors for these enzymes were tested. Sodium orthovanadate, sodium fluoride, levamizole, and ammonium molybdate had no effect on the ATPase activities. In the absence of Mg(2+) (basal activity), the apparent K(m) for ATP(4-) was 0.053 +/- 0.008 mM, whereas at saturating MgCl(2) concentrations, the corresponding apparent K(m) for Mg-ATP(2-) for Mg(2+)-dependent ecto-ATPase activity (difference between total and basal ecto-ATPase activity) was 0.503 mM +/- 0.062. Both ecto-ATPase activities were highly specific for ATP and were also able to hydrolyze ADP less efficiently. To identify the observed hydrolytic activities as those of an ecto-ATPase, we used suramin, a competitive antagonist of P(2) purinoreceptors and an inhibitor of some ecto-ATPases, as well as the impermeant agent 4'-4'-diisothiocyanostylbenzene-2'-2'-disulfonic acid. These two reagents inhibited the Mg(2+)-independent and the Mg(2+)-dependent ATPase activities to different extents, and the inhibition by both agents was prevented by ATP. A comparison among the ecto-ATPase activities of three amoeba species showed that the noninvasive E. histolytica and the free-living E. moshkovskii were less efficient than the pathogenic E. histolytica in hydrolyzing ATP. As E. histolytica is known to have a galactose-specific lectin on its surface, which is related to the pathogenesis of amebiasis, galactose was tested for an effect on ecto-ATPase activities. It stimulated the Mg(2+)-dependent ecto-ATPase but not the Mg(2+)-independent ATPase activity.

Common presentations of amebic liver abscess

STUDY OBJECTIVE

The most common extraintestinal manifestation of Entamoeba histolytica, the agent of amebiasis, is a hepatic abscess. This infection is common throughout the world and can be associated with life-threatening consequences. Given the often nonspecific nature of the complaints related to an amebic abscess, a retrospective review of patients with confirmed disease was done to recognize the most common patterns of presentation.

METHODS

A retrospective case series was conducted of all patients with confirmed amebic liver abscess over a 5-year period. All available emergency department and inpatient records were reviewed. Age, sex, country of origin, chief complaint (including duration), vital signs, and physical and laboratory findings were recorded. The use of ultrasonography, computed tomography scan, chest radiograph, and serum antibodies was noted, as well as the final ED diagnosis.

RESULTS

Seventy-five patients were reviewed; mean patient age was 35.5 years, 80% were male, and Mexico was the country of origin for 64%. The most common complaint was fever (77%), followed by abdominal pain (72%), which was most often located in the right upper quadrant. Cough (16%), chest pain (19%), and chest radiographic abnormalities (57%) were also common. The majority of patients (69%) had symptoms for less than 13 days. The WBC count was the most consistent laboratory abnormality (83%), whereas the liver aminotransferase, alkaline phosphatase, and bilirubin levels were often normal. Most patients received their diagnoses on the basis of ultrasonography (85%), followed by a confirmatory serum antibody titer (88%). The diagnosis of amebic liver abscess was correctly made in the ED in 31.5% of the patients, with the most common misdiagnoses being cholecystitis (16.4%), hepatitis (12.3%), and pneumonia (9.6%).

CONCLUSION

Patients with amebic liver abscess do present to EDs in the southwestern United States, especially in areas with a high immigrant population from endemic areas. Patients with complaints of fever and right upper quadrant abdominal pain, especially men of Hispanic origin, warrant a high degree of vigilance. Whereas most laboratory studies are unhelpful, the diagnosis can often be made in the ED by means of a bedside ultrasonographic test. Treatment should be initiated with metronidazole with disposition to an inpatient medical service.

Spectrum of complicated intestinal amebiasis through resected specimens: incidence and outcome

BACKGROUND/PURPOSE

Entamoeba hystolytica (EH) is an enteric protozoan that may cause serious complications that require operative management in children. A retrospective clinical trial was performed to find out the incidence and outcome of complicated intestinal amebiasis (IA) by means of surgically resected specimens in children.

METHODS

The histopathologic evaluation of 554 intestinal specimens (including appendix and polyp) of 482 patients between 1980 and 1997, inclusive, were reviewed. Intestinal biopsy specimens taken from successfully medically treated patients with uncomplicated IA were excluded.

RESULTS

Complicated IA was noted in 18 children (3.7%) consisting of 7 girls and 11 boys with a mean age of 9.2+/-2.3 years. EH was present in the (1) appendices of 4 patients with perforated appendicitis and 3 patients with normal appendix who underwent negative exploration; (2) juvenile polyps of 4 patients presenting with hematochesia; (3) colonic wall of 1 patient presenting with intussusception and treated by resection and anastomosis; (4) cecum of 1 patient presenting with right lower quadrant mass and underwent exploration with the presumptive diagnosis of lymphoma; (5) colonic wall of 5 patients who underwent ileostomy followed by subtotal colectomy and endorectal pull-through with the presumptive diagnosis of chronic inflammatory bowel disease (n = 3), toxic megacolon + peritonitis (n = 1), and total colonic polyposis (n = 1). All above-mentioned patients are alive and free of symptoms.

CONCLUSIONS

The diagnosis of IA should be considered in a very wide spectrum of clinical appearances. IA may be associated with colonic polyps and perforated appendicitis, may act as a leading point for intussusception, and may mimic the clinical picture of appendicitis and lymphoma resulting in negative explorations. The diagnosis and treatment of complicated IA in patients who received a misdiagnosis of inflammatory bowel disease is a great challenge and requires major and emergency surgery.

First report of invasive amebiasis in an organ transplant recipient

T-cell mediated immunity is an important defense mechanism against amebiasis. However, organ transplant recipients with severe T-cell immunosuppression are not at increased risk of having Entamoeba histolytica invasive disease. The reasons are unclear and probably multifactorial, but it is likely that the absence of intestinal colonization with pathogenic strains in countries where transplants occur and the judicious intake of possible contaminated food and water are important contributing factors. We describe the first report of a liver transplant recipient with severe E. histolytica colitis who was successfully treated with metronidazole without modifying his immunosuppression therapy.

Parasites and Diarrhea. I: Protozoans and Diarrhea

Intestinal parasitism is extremely common, with approximately 70% of all people harboring one or more intestinal parasite. Parasitism and diarrhea are both hyperendemic in areas where sanitation is suboptimal. Many clinicians assume that the identification of intestinal parasites in patients with diarrhea implies that the parasites are the cause. This approach is frequently misguided. Some intestinal parasites such as Giardia lamblia and Entamoeba histolytica certainly do cause diarrhea. Others, for example Entamoeba coli and Ascaris lumbricoides, almost certainly do not. In addition, there are a number of other organisms that have been associated with diarrheal illness in some cases, which may or may not be important pathogens. In this article, we will review the role of protozoans as definite and possible causes of diarrhea. In Part II, we review the role of helminths in diarrhea.

Dientamoeba fragilis. An unusual intestinal pathogen

This is a case report of a gastrointestinal infection caused by Dientamoeba fragilis. It is a flagellate protozoan that is an uncommon etiology of gastrointestinal disease. Primarily characterized by diarrhea and abdominal pain, other symptoms such as flatulence, nausea, vomiting, fatigue, malaise, and weight loss occur. Diagnosis is made using multiple fresh stool samples that are preserved and permanently stained looking for the typical binucleate trophozoite. Since there is a distinct association with Enterobius vermicularis (possibly the mode of protozoan transmission), the human pinworm is also sought. Treatment of choice consists of diiodohydroxyquin in adults and metronidazole in children.

Parasitic infections of the central nervous system in children. Part III: Space-occupying lesions

In the last part of this three-part review of parasitic infections of the central nervous system in children, we consider parasites which due to their size, distribution, or the nature of the host response, tend to cause focal lesions in the brain and spinal cord and therefore present as space-occupying lesions which occasionally mimic malignant tumors. As in Parts I and II, infections are grouped according to their predominant geographic area. Such infections include cysticercosis, one of the more common and important infections of the central nervous system.

Febrile illness caused by parasites

Febrile patients in whom a parasitic etiology is suspected can be classified broadly into two categories for the purpose of diagnostic evaluation based on the presence or absence of accompanying eosinophilia. Generally, the absence of eosinophilia indicates a protozoan etiology while the presence of eosinophilia is associated with tissue-invasive helminthic infections. The history and physical examination often points to a specific diagnosis that can be confirmed by appropriate laboratory tests.