Amoebiasis

Clinical manifestations and endoscopic findings of amebic colitis in a United States-Mexico border city: a case series

Background

Invasive amebiasis is not frequently seen in the United States. It is associated with considerable morbidity in patients residing in or traveling to endemic areas. We report a case series of patients with amebic colitis in a United States-Mexico border city to alert physicians to the varied clinical manifestations.

Case presentation

Nine patients were diagnosed with amebic colitis. Mean age was 56 (38–83), 6 were males, and all were Hispanic. Common symptoms were diarrhea (56 %), hematochezia (33 %) and abdominal bloating (11 %). The diagnosis of amebic colitis was established in the following ways: 8 patients by colonoscopy with biopsy, 1 by surgery for colonic obstruction. The diagnosis of amebic colitis was confirmed in 8 patients (89 %) by amebic trophozoites present in histopathologic sections. One patient was diagnosed with amebic colitis based upon clinical symptoms, colitis on colonoscopy and visualization of amebic trophozoites on stool examination. In the 8 patients in whom colonoscopy was done, 6 (75 %) had inflammation with rectosigmoid involvement and 5 (62.5 %) had ulcerations. Infection resolved after treatment with metronidazole in most patients; however, one patient developed a liver abscess and another had a colonic perforation and later developed a liver abscess.

Conclusion

The occurrence of amebic colitis in this United States-Mexico border city hospital population was low, but in some cases potentially life-threatening. Physicians should be alert to the less common presentations of amebic colitis, such as overt gastrointestinal bleeding, exacerbation of inflammatory bowel disease, and the incidental finding of association with colon cancer, or a surgical abdomen. Rectosigmoid involvement was typically found on colonoscopy.

Fulminant amoebic colitis during chemotherapy for advanced gastric cancer

A 52-year-old man had bloody stools during chemotherapy for gastric cancer. A colonoscopy revealed necrotizing ulcer-like changes. A biopsy confirmed the presence of amoebic trophozoites. Subsequently, peritonitis with intestinal perforation developed, and emergency peritoneal lavage and colostomy were performed. After surgery, endotoxin adsorption therapy was performed and metronidazole was given. Symptoms of peritonitis and colonitis resolved. However, the patient’s general condition worsened with the progression of gastric cancer. The patient died 50 d after surgery. Fulminant amoebic colitis is very rarely associated with chemotherapy. Amoebic colitis should be considered in the differential diagnosis of patients who have bloody stools during chemotherapy.

Amebic Colitis Can Mimic Tuberculosis and Inflammatory Bowel Disease on Endoscopy and Biopsy

Biopsies of 11 patients with histopathologically diagnosed amebic colitis was evaluated; endoscopically, they were suspected to have tuberculosis or inflammatory bowel disease. Amebiasis was suggested in the differential diagnosis in only 3 cases. Three patients had purely rectal or sigmoid involvement, whereas the others had ileocecal, cecal, ascending, or transverse colon disease. The biopsies showed cryptitis and depletion of mucin but no crypt branching. Crypt abscesses were seen in one biopsy. Trophozoites of Entamoeba histolytica were seen in the exudate in all cases. The trophozoites were round to oval, approximately 25 to 40 µm in diameter and had a single, round nucleus and periodic acid-Schiff—positive cytoplasm. Phagocytosed erythrocytes were present in the trophozoites. Some features of ulcerative colitis and infectious colitis, such as cryptitis and crypt abscesses, are also seen in amebic colitis. Amebic colitis must be included in the differential diagnosis of all patients with suspected inflammatory bowel disease and tuberculosis.

Species-specific field testing of Entamoeba spp. in an area of high endemicity

Entamoeba histolytica has been separated in recent years into 2 morphologically identical species: the apathogenic E. dispar and the pathogenic E. histolytica, only the latter being pathogenic. Although various laboratory techniques allow discrimination between the 2 species there is a lack of field data about the suitability of available diagnostic tests for use in epidemiological studies and few epidemiological studies using species-specific diagnosis have been performed at community level in endemic areas, especially in sub-Saharan Africa. We conducted a repeated cross-sectional study of 967 schoolchildren in central Côte d'Ivoire to compare and evaluate light microscopy, 2 different antigen detection assays, and one polymerase chain reaction (PCR) assay. Microscopy and a non-specific antigen capture Entamoeba enzyme-linked immunosorbent assay (ELISA) were used for the primary screening of all children (time t0). The prevalence of the E. histolytica/E. dispar species complex at t0 was 18.8% by single microscopical examination and 31.4% using the non-specific ELISA. Approximately 2 months after the initial screening, fresh stool specimens were collected on 2 consecutive days (t1 and t2) from (i) all the children who were positive by microscopy at t0 (n = 182) and (ii) 155 randomly selected children who were negative at the primary screening. These samples were tested with a second antigen detection ELISA specific for E. histolytica (n = 238) and with a species-specific PCR assay (n = 193). The second and third examinations (t1 and t2) revealed an additional 43 infections with the species complex E. histolytica/E. dispar, so that the cumulative microscopical prevalence for t1 and t2 was 27.7%. The overall prevalence of E. histolytica by species-specific ELISA antigen detection was low (0.83%), while the prevalence of E. dispar was 15%. When analysing only microscopically positive samples by PCR (n = 129), the ratio E. histolytica: E. dispar was very low (1:46), suggesting that the vast majority of Entamoeba infections in this area were apathogenic. Both species-specific tests performed well but the ELISA was easier to use for large-scale field screening.

Asymptomatic amebic colitis in a homosexual man

We describe case of a 75-yr-old Japanese homosexual man who was diagnosed as having amebic colitis. The present case is unique in that invasive amebiasis has occurred in a homosexual man, because Entamoeba histolytica in homosexual patients is considered to be a nonpathogenic and commensal organism in western countries, and that the patient has not complained of any gastrointestinal symptoms associated with minute colonic lesion of an isolated cecal ulcer. This report indicates that the absence of gastrointestinal symptoms does not rule out invasive amebiasis. Therefore, once the ameba is identified in stool specimens, even in homosexual men, it is important to differentiate pathogenic from nonpathogenic species irrespective of whether the patient is symptomatic, and to treat the patient infected with pathogenic species. By means of this strategy, we can prevent pathogenic ameba from spreading in the community.

Fulminant amebic colitis. A morphologic study of four cases

PURPOSE

The morphologic features of fulminant amebic colitis are poorly documented. In this report, we describe the clinical and pathologic findings in four of these cases.

METHODS

The surgical pathology reports and accompanying histologic slides were examined from four patients who underwent surgical resections for fulminant amebic colitis. Clinical information was obtained from the patients' medical records.

RESULTS

Large, geographic mucosal ulcers were typically present and were accompanied by yellow-green pseudomembranes. The muscularis externa was usually attenuated and necrotic, imparting a "wet blotting paper" consistency. Large numbers of amebic trophozoites were present within the inflammatory exudates. The mucosa adjacent to and undermined by the ulcers was often hemorrhagic or inflamed, resembling ischemic colitis or idiopathic inflammatory bowel disease, respectively. Two patients died within four weeks of their surgery. A third patient died one year later as a result of AIDS-related complications. The remaining patient has been lost to follow-up.

CONCLUSION

An uncommon but life-threatening manifestation of intestinal amebiasis is a fulminant colitis. Early surgical intervention and intensive antiamebic chemotherapy are essential for efficacious management.

Fatal amoebic liver abscess: an autopsy study

An autopsy study of 20 cases is presented. The mean age was 32 years (range: 14-45). Four cases (20%) presented with jaundice. Another four (20%) had continuous fever with abdominal pain. Six had loose motions with blood and mucus in the stools. The mean duration of illness was 7.2 days. All cases were thin and emaciated. Liver was grossly enlarged (mean weight: 2680 g). The abscess was single in all cases except one. The right lobe was involved in 15 cases, the left in four and both in one. The average size of abscess was 13 cm. The abscess had ruptured in the abdomen in 3 patients, for which laparotomy was performed. Pulmonary involvement was seen in 3 cases. Colon showed ulceration in half the patients. In 2 cases perforation was also present. No cerebral involvement was present. A number of interesting features emerged from this study. Although amoebic liver abscess is a common disease, its diagnosis can be missed due to unusual presentation. In the present study, diagnosis of viral hepatitis, carcinoma lung, bacillary dysentery and enteric fever with perforation were made, which probably contributed materially to fatal outcome.

Amoebic liver abscess: the effect of aspiration on the resolution or healing time

Recent sonographic monitoring of patients treated for amoebic liver abscess has shown the healing or resolution time varying between 10 and 300 days. The effect of percutaneous needle aspiration under or resolution time was studied in 36 patients. Nineteen patients had drugs and needle aspiration under ultrasound guide whilst the 17 patients had drugs--metronidazole, diloxanide, and chloroquine--alone. Both groups were monitored clinically and sonographically. Results showed that the abscess cavities of 18 out of 19 patients (94.7%) of the aspirated group and 10 of 17 patients (58.8%) of the non-aspirated group had resolved at the end of three weeks. The difference in response to treatment was significant (P less than 0.02) more so for lesion size more than 6 cm (P less than 0.01). There was also a more rapid clinical response in the aspirated group than in the non-aspirated group, particularly for patients whose lesion size was more than 6 cm (P less than 0.01). In conclusion, percutaneous needle aspiration is safe, enhances clinical recovery, and accelerates resolution particularly in patients with large abscess cavities.

Secretory hydrolases of Entamoeba histolytica

Cells of Entamoeba histolytica grown over a period of four days contained NADP+-dependent alcohol dehydrogenase exclusively inside the cells. No activity of this enzyme could be found in the growth medium after harvesting the cells. Under the same conditions, acid phosphatase, beta-N-acetylglucosaminidase, esterase, alpha-glucosidase, and different amylases of the parasite were found both inside the cells and in the medium. The activities present in the cell homogenate and in the medium before and after growth of the amoebas were partially separated by gel filtration on Sephadex G150 and G75, respectively. The comparison of the elution diagrams revealed that NADP+-dependent alcohol dehydrogenase, acid phosphatase, esterase, and amylases occurred as multiple forms inside the cells. These activities, as well as beta-N-acetylglucosaminidase and alpha-glucosidase, were released into the extracellular environment to a different degree. The enzymes originating from the parasite were identified and distinguished from those of the ingredients of the growth medium according to their molecular mass and pH optimum. Furthermore, the amoebic origin of the secreted enzymes was shown on the basis of their inhibition by antibodies prepared against the supernatant fraction of the homogenate.

Endoscopic examination of the colon in infancy and childhood

Flexible fiberoptic colonoscopy is a safe and effective diagnostic procedure in infants and children. It is a sensitive and practical procedure that has made substantial contributions to the diagnosis and treatment of colonic disorders in infants and children. With further refinements in technique, future applications of its use are likely to occur.

Diagnosis of Meleney's synergistic gangrene

A retrospective and comparative study of 127 case reports of Meleney's postoperative progressive synergistic gangrene and of 62 examples of postoperative amoebic skin gangrene, showed that these two entities were clinically indistinguishable and that therefore a purely clinical diagnosis of Meleney's gangrene could not be made. Furthermore, a critical appraisal of the bacteriological data indicated that a certain diagnosis of Meleney's gangrene cannot be provided by the clinical bacteriologist. Finally, the histological features were entirely non-specific thus precluding a definitive diagnosis by the histopathologist. If Meleney's entity cannot be diagnosed its existence becomes debatable. The alternative diagnosis of cutaneous amoebiasis is advanced for consideration. Several of the outstanding features of Meleney's progressive gangrene, hitherto unexplained, are better understood if Entamoeba histolytica is accepted as the prime cause rather than bacteria.

An outbreak of amoebic infection in a kibbutz population

The cause of a reported outbreak of abdominal cramps and diarrhoea in a kibbutz in the Western Negev, Israel, was sought. Over 25% of the kibbutz population was found to harbour Entamoeba histolytica, a very high rate by Israeli standards. The highest frequency of infection was in the nought to nine-year-old group. High frequencies were also observed among 30- to 49-year-old women. The sanitary and hygienic conditions in the kibbutz, checked at the time of the epidemic and five years later, were extremely poor. These findings support the generally accepted idea of the close relationship between personal hygiene, sanitary food conditions and amoebic infection.

Parasitic bowel disease: three pathogens important in primary care

A high index of suspicion and careful application of diagnostic methods are essential for accurate diagnosis of parasitic bowel diseases. The varied clinical spectrum of giardiasis, amebiasis, and strongyloidiasis emphasizes the need to consider these pathogens when patients present with gastrointestinal complaints. Giardiasis should be suspected in patients, especially returned travelers, with unexplained increase in stool frequency, particularly with bloating, flatulence, or vague systemic symptoms. Amebiasis must be considered in the differential diagnosis of any patient who presents with persistent diarrhea or signs of inflammatory bowel disease. Unexplained diarrheal illnesses associated with upper abdominal symptoms and eosinophilia should raise suspicion of the presence of strongyloidiasis. These findings in a patient with a compromised immune system or in a candidate for immunosuppressive therapy should prompt a thorough investigation to rule out this parasite, since disseminated strongyloidiasis often is fatal.