Outcome of untreated infection with Entamoeba histolytica in homosexual men with and without HIV antibody

Enteric Infections in Men Who Have Sex With Men

BACKGROUND

Enteric pathogens are often associated with exposure to food, water, animals, and feces from infected individuals. However, in sexual networks of men who have sex with men (MSM), transmission of enteric pathogens may occur during direct or indirect oral-anal contact.

METHODS

We performed a scoping review of the literature for studies prior to July 2019 with key terms for gastrointestinal syndromes ("proctitis," "enteritis," "proctocolitis"), enteric pathogens or sexually transmitted infections (STIs), and outbreaks using multiple electronic databases.

RESULTS

We identified 5861 records through database searches, bibliography reviews, and keyword searches, of which 117 references were included in the pathogen-specific reviews.

CONCLUSIONS

The strength of observational data describing enteric pathogens in MSM and possible sexual transmission of enteric pathogens varies by pathogen; however, a robust body of literature describes the sexual transmission of Campylobacter, Giardia lamblia, and Shigella (particularly antimicrobial-resistant strains) in sexual networks of MSM. Providers are encouraged to consider enteritis or proctocolitis in MSM as possibly having been sexually transmitted and encourage targeted STI testing. Risk/harm reduction and prevention messages should also be incorporated, though there is an acknowledged paucity of evidence with regards to effective strategies. Further research is needed to understand the transmission and prevention of enteric pathogens in MSM.

Entamoeba histolytica infection in men who have sex with men

Entamoeba histolytica infection (amoebiasis) is the second leading cause of death from parasitic diseases. Epidemiological studies from developed countries have reported an increasing prevalence of amoebiasis and of invasive infections, such as amoebic colitis, among men who have sex with men (MSM) who engage in oral-anal sex. Although most infections with E histolytica are asymptomatic, clinical manifestations of invasive amoebiasis mainly include amoebic colitis and amoebic liver abscess, which are associated with substantial morbidity and medical cost. Laboratory diagnosis of amoebiasis should be based on detection of E histolytica by use of tests with high sensitivity and specificity, such as specific amoebic-antigen or PCR-based assays. Microscopy used in routine clinical laboratories is not sensitive or specific enough for detection of E histolytica. Metronidazole or tinidazole remains the mainstay of treatment for invasive amoebiasis, followed by treatment with luminal agents to prevent relapse and transmission of E histolytica to sexual partners or close contacts.

Treatment of symptomatic amebic colitis in human immunodeficiency virus-infected persons

While most Entamoeba histolytica appearing in male homosexuals infected with human immunodeficiency virus (HIV) is considered non-invasive in Western countries, and treatment of amebiasis in these persons has received very little attention, in Japan some male homosexual amebiasis patients infected with HIV complain of symptoms attributable to E. histolytica infection. We investigated whether symptomatic E histolytica amebic colitis in HIV-infected persons requires higher doses or longer duration of antiamebic drug therapy than in non HIV-infected patients. Four symptomatic amebic colitis patients infected with HIV-1, three of them severely immunocompromised, with CD4 cell counts <200/mm(3), were treated with oral metronidazole: 1500 mg a day for 10 days in 2 patients, 1000 mg a day for 10 days in 1 patient, and 1000 mg a day for 6 days and then 750 mg for 4 days in 1 patient, and good therapeutic results with no side effects were obtained. This indicates that symptomatic amebic colitis in HIV-infected persons can be successfully treated with metronidazole at the same dose and duration of treatment used in non-HIV-infected persons.

Sexual transmission of intestinal parasites in men who have sex with men

Direct oral-anal sexual contact is a common practice among men who have sex with men (MSM) and is implicated in the transmission of various enteric pathogens including intestinal parasites. The present study reviewed data on the sexual transmission of intestinal parasites among MSM, and highlighted advances in the diagnosis of such infections. The emergence and spread of intestinal parasites is of public health concern particularly in the homosexual community. Intestinal parasitic infection should be considered in the differential diagnosis of gastrointestinal disease in this population. Combination of traditional diagnostic procedures with implementation of testing based on novel molecular methods in the accurate identification of intestinal parasites is important so that early intervention and control of infection is facilitated.

Amebiasis cutis revisited

BACKGROUND

Amebiasis cutis (AC) is reported infrequently. This study assesses the clinicopathological spectrum, co-existent visceral involvement and impact of human immunodeficiency virus (HIV) co-infection on AC.

METHODS

An 8-year prospective clinicopathological evaluation of patients with AC.

RESULTS

Thirty-one biopsies of ulcers, fistulae, fissures, abscesses, polypoid and warty lesions in perianal, penile, scrotal, vulval, buttock, chest and abdominal wall sites were evaluated. Of these, 11 had a 'superficial' (superficial AC) and 20 a 'deep' (deep AC), histopathological pattern. Superficial AC showed predominant epidermal spongiosis, liquefactive necrosis, ulceration and fissures with hematophagous amebic trophozoites (HATs). Deep AC had confluent deep dermal and subcutaneous liquefactive, coagulative or suppurative necrosis and HATs. Seven biopsies showed vasculitis or thrombosis with luminal HATs.

OUTCOME

Fourteen patients died; 9 had concomitant visceral amebiasis, 5 had other co-infections. Six who died were HIV seropositive, three were seronegative; all had deep AC. Of the 17 survivors, 11 (8 HIV positive) had superficial AC that healed with metronidazole treatment; the remaining 6 (one HIV seropositive) required additional surgical intervention.

CONCLUSION

Deep AC is predictive of co-existent, contiguous visceral disease. The effective management, histopathological mimickers and diagnostic pitfalls of superficial and deep AC differ. The outcome in HIV-infected patients is dependent on co-existent systemic diseases.

Molecular methods for diagnosis of Entamoeba histolytica in a clinical setting: an overview

The range of clinical outcomes following Entamoeba histolytica infection is likely to be influenced by the different strains of the parasite already existing in our population. There is a need for developing faster, reliable and reproducible methods for identifying the different strains of E. histolytica. This would have a major impact on the subsequent course of treatment given to patients. In the post-genomic era, different loci of the Entamoeba genome have been targeted for developing suitable probes and genetic markers. This review highlights the development made in this direction and the possibility of using these methods for routine testing of this parasite in clinical samples.

Diversity of clinical isolates of Entamoeba histolytica in Japan

In Japan, amebiasis is domestically transmitted by two major populations: male homosexuals and mentally handicapped persons, which is remarkably different from most other developed countries where Entamoeba dispar infection is predominantly observed. Here we briefly summarize epidemiology of amebiasis in Japan. We also review our current understanding of the diversity of Entamoeba histolytica clinical isolates in Japan, based on polymorphic genetic markers, clinical representations, and in vivo virulence, using an animal model.

Restricted entry of R5 HIV Type 1 strains into eosinophilic cells

A cell culture system previously developed by our laboratory demonstrated that T cell-tropic (CXCR4-using) but not macrophage-tropic (CCR5-using) HIV-1 strains productively infected eosinophilic cells. In the current study, an improved model was used to determine the level of this viral restriction by assessing viral entry and coreceptor usage. The model was improved by using AML14.3D10 cells that were engineered to express CCR3 in addition to the major HIV-1 coreceptors, CD4, CXCR4, and CCR5, thus making them more like primary eosinophils. A polymerase chain reaction (PCR) assay was used to detect viral entry. In the PCR assay, primers specific for early reverse transcription products were used to amplify minus strand viral DNA from HIV-1-infected AML14.3D10-CCR3 eosinophilic cells. Coreceptor blocking experiments, using the CXCR4 antagonist AMD3100, were performed to determine coreceptor usage by the CXCR4-using (X4) strain known to productively infect the cells. Virus production was measured by p24 immunoassay. As expected, viral DNA was detected in AML14.3D10-CCR3 cells infected with X4 HIV-1, and cell viability was decreased during maximal viral production. Conversely, viral DNA was not detected in eosinophilic cells exposed to a CCR5-using (R5) HIV-1 strain that is also capable of using CCR3, indicating that R5 HIV-1 is unable to enter eosinophilic cells despite the presence of the appropriate coreceptors. Infection of AML14.3D10-CCR3 cells by HTLV-III(B) was completely inhibited by AMD3100, indicating that X4 HIV-1 enters the AML14.3D10-CCR3 cell line by using the CXCR4 coreceptor exclusively. Since X4 strains predominate during the late stages of HIV-1 infection in many patients, when eosinophil numbers also tend to increase, the ability of these HIV-1 strains to infect eosinophilic cells has important implications for the involvement of eosinophils in the pathogenesis of AIDS.

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.

Longitudinal study of intestinal Entamoeba histolytica infections in asymptomatic adult carriers

To gain insight into the dynamics of intestinal Entamoeba histolytica infection, a longitudinal study was performed over an observation period of 15 months with a group of 383 randomly selected adult individuals (mean age, 38.5 years) living in an area of amebiasis endemicity in central Vietnam. Ameba infection was diagnosed by using species-specific PCR and DNA extracted directly from fecal samples. The results indicated an E. histolytica prevalence of 11.2% and an annual new infection rate of 4.1% in the study population. Follow-up of the 43 individuals who were E. histolytica positive at enrollment suggested a regular exponential decline in infection of about 3% per month and a mean half-life of infection of more than 15 months. However, the reinfection rate for this group of participants was 2.7 times higher than that predicted for the study population as a whole. Both the reappearance of the parasite after successful treatment of E. histolytica infection and changes in "genetic fingerprints" of parasites during the course of infection revealed an annual new infection rate of about 11.5%. Thus, the mean half-life of E. histolytica infection was calculated to be 12.9 months (95% confidence interval, 10.2 to 15.6 months). Notably, none of the participants developed symptoms compatible with invasive intestinal amebiasis, and only one of the subjects developed an amebic liver abscess during the observation period.

Proctitis and Sexually Transmissible Diseases of the Colon

In patients with gastrointestinal symptoms and a history of anal-receptive intercourse, a careful but explicit history concerning sexual preferences and practices is required. Clinically, four infectious syndromes can be distinguished: perianal disease, proctitis, proctocolitis, and enteritis. Each of these syndromes may be caused by a certain range of pathogens. In immunocompromised patients, additional diseases must be considered. Clinical examination, a rectal swab with incubation in specific transport media, as well as a Gram stain of mucus or pus from a rectal swab, in combination with a rectosigmoidoscopy are helpful in differentiating specific diseases. Stool cultures and serologic examinations may identify specific causes of colitis or enteritis, but are of minor importance in the case of anorectal disease. Good treatments are available for most sexually transmitted anorectal diseases. An additional role for the treating physician and other healthcare providers is to educate and counsel patients and their sex partners on ways to adopt safer sexual behavior.

Entamoeba histolytica/Entamoeba dispar infections in human immunodeficiency virus-infected patients in the United States

We describe the incidence of and laboratory and clinical characteristics associated with Entamoeba histolytica/Entamoeba dispar infection diagnosed in human immunodeficiency virus (HIV)-infected persons enrolled in the Adult and Adolescent Spectrum of HIV Disease Project. From 1 January 1990 to 1 January 1998 (82, 518 person-years of follow-up), 111 patients (98% men) were diagnosed with E. histolytica/E. dispar infection. Among HIV-infected patients in the United States, the incidence of diagnosed E. histolytica disease is low (13.5 cases per 10,000 person-years [95% confidence interval, 7.7-22.2], with diagnosis most common in those patients exposed to HIV through male-male sex.

Cysteine proteinases and the pathogenesis of amebiasis

Amebiasis is a major cause of morbidity and mortality throughout the tropical world. Entamoeba histolytica is now recognized as a separate species from the morphologically identical E. dispar, which cannot invade. Cysteine proteinases are a key virulence factor of E. histolytica and play a role in intestinal invasion by degrading the extracellular matrix and circumventing the host immune response through cleavage of secretory immunoglobulin A (sIgA), IgG, and activation of complement. Cysteine proteinases are encoded by at least seven genes, several of which are found in E. histolytica but not E. dispar. A number of new animal models, including the formation of liver abscesses in SCID mice and intestinal infection in human intestinal xenografts, have proven useful to confirm the critical role of cysteine proteinases in invasion. Detailed structural analysis of cysteine proteinases should provide further insights into their biochemical function and may facilitate the design of specific inhibitors which could be used as potential chemotherapeutic agents in the future.

Cysteine proteinases and the pathogenesis of amebiasis

Amebiasis is a major cause of morbidity and mortality throughout the tropical world. Entamoeba histolytica is now recognized as a separate species from the morphologically identical E. dispar, which cannot invade. Cysteine proteinases are a key virulence factor of E. histolytica and play a role in intestinal invasion by degrading the extracellular matrix and circumventing the host immune response through cleavage of secretory immunoglobulin A (sIgA), IgG, and activation of complement. Cysteine proteinases are encoded by at least seven genes, several of which are found in E. histolytica but not E. dispar. A number of new animal models, including the formation of liver abscesses in SCID mice and intestinal infection in human intestinal xenografts, have proven useful to confirm the critical role of cysteine proteinases in invasion. Detailed structural analysis of cysteine proteinases should provide further insights into their biochemical function and may facilitate the design of specific inhibitors which could be used as potential chemotherapeutic agents in the future.

Invasive amoebiasis: an emerging parasitic disease in patients infected with HIV in an area endemic for amoebic infection

OBJECTIVES

To describe the incidence and presentations of invasive amoebiasis (IA) in patients with HIV infection in an area endemic for amoebic infection and to assess the role of the indirect haemagglutination (IHA) assay in the diagnosis of IA in HIV-infected patients.

DESIGN

Retrospective study of 18 cases of IA and HIV infection.

SETTING

A university hospital, the largest centre for management of HIV-associated complications in Taiwan.

METHODS

Medical, microbiological and histopathological records of 296 HIV-infected patients and serological data of IHA assay of 126 HIV-infected patients were reviewed to identify cases of IA from 23 June 1994 to 31 March 1999. An IHA titre > or = 1 : 128 was considered positive. Clinical characteristics of HIV-infected patients with IA and without IA were compared.

RESULTS

Eighteen of the 296 patients (6.1%) with HIV infection were diagnosed with IA: 12 patients were diagnosed with definite IA and six with probable IA. The clinical manifestations included amoebic colitis (13 patients), amoebic liver abscess (nine), both colitis and abscess (four), and pleural effusion (two). IA was the initial presentation of HIV infection in nine patients. Co-infection with other enteric pathogens was diagnosed in six patients with IA. Compared with the 161 patients without IA who were newly diagnosed with HIV infection, the nine patients with IA had a higher median CD4+ lymphocyte count (202 x 10(6)/l versus 33 x 10(6)/l; P = 0.0017), were less likely to be diagnosed with AIDS (55.6% versus 85.4%; P = 0.039), and had fewer concurrent AIDS-defining illnesses (median number 0 versus 2; P = 0.003). Estimated mean survival duration was not significantly different between the two groups (597 days versus 611 days). Fourteen out of 126 patients (11.1%) had an IHA titre > or = 1 : 128. Of the 18 patients diagnosed with IA, 13 had a titre > or = 1 : 128. The sensitivity of IHA assay in the diagnosis of IA was 72.2% (13 out of 18) and the specificity was 99.1% (107 out of 108). The positive predictive value of IHA test for IA of this patient population was 92.9% (13 out of 14) whereas the negative predictive value was 95.5% (107 out of 112).

CONCLUSION

IA is an increasingly important parasitic disease among patients with HIV infection in Taiwan. IHA assay has a good specificity and high negative predictive value in diagnosis of IA.

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.

Invasive amoebiasis in two patients with AIDS and cytomegalovirus colitis

Homosexual persons or human immunodeficiency virus (HIV)-infected patients frequently excrete cysts of nonpathogenic strains of Entamoeba histolytica ("Entamoeba dispar"). However, invasive amoebiasis is rare. We report two patients with AIDS and cytomegalovirus colitis in whom invasive amoebiasis was histologically diagnosed. It is concluded that E. histolytica has to be considered in HIV-infected patients with colitis.

Gastrointestinal pathology in HIV-infected patients

Specific pathologic processes, particularly oral, esophageal, and intestinal infections, are common in the alimentary tract of AIDS patients. Many of these diseases are adequately assessed only by biopsy with histologic examination. Most are rare or unreported in immunocompetent hosts and are easily missed by those not familiar with them. This article describes the gross or endoscopic and histologic appearances and the diagnostic criteria for enteric pathologic processes seen in HIV-infected individuals.

Analysis of 69 patients with amebic liver abscess

All 69 patients with amebic liver abscess that we treated in 1981-1992 were studied retrospectively. Men predominated by a 10:1 ratio. Of our 227 patients with amebiasis, some 30% yearly had liver involvement. The incidence peaked in 1988, decreasing later but increasing again in 1992. Most patients were 30-50 years old, the overall mean age being 45 years (range, 22-79), and decreasing with time. Patients with the related factors of travel abroad, positive results of a test for Treponema pallidum hemagglutination, and homosexuality have increased in number in recent years. Fever, abdominal pain, and hepatomegaly were the most frequent findings, and 39 patients had neither bloody stools nor diarrhea. Only 8 patients had had amebiasis previously. A solitary abscess in the right lobe of the liver was found in 40 patients. Entamoeba histolytica was found in the stool of 31 patients and in the pus of 39 patients. Sixty-one patients had positive results for an amebic serological test(s). The abscesses ruptured into the peritoneal cavity in 4 patients. All patients received metronidazole. Percutaneous or surgical drainage (or both) was done in 62 patients. The outcome was good, with 1 exception, and only 2 patients had recurrences.

Value of microscopy in the diagnosis of dysentery associated with invasive Entamoeba histolytica

AIMS

To assess the reliability of the detection of erythrophagocytic amoebic trophozoites in stool samples in the diagnosis of dysentery associated with invasive Entamoeba histolytica.

METHODS

Amoebic culture was carried out on single stool samples collected from patients from Mexico, Colombia, and Bangladesh. The stools had been examined by light microscopy. Amoebic dysentery was diagnosed when erythrophagocytic E histolytica trophozoites were observed in a case of bloody diarrhoea. E histolytica isolates were characterised by isoenzyme electrophoresis and results correlated with microscopical findings in stools. Statistical analysis was performed using the chi 2 test.

RESULTS

Where erythrophagocytic amoebae had been observed in dysenteric stool specimens the E histolytica phenotype was invariably invasive (p < 0.0001). Observation of erythrophagocytic amoebae in dysentery is 100% specific and predictive of infection with invasive E histolytica. When amoebic culture-positive cases only are considered it is 96% sensitive. In this study E histolytica of zymodeme XIV was more commonly associated with amoebic dysentery than zymodeme II. There was no significant difference between the carriage rate of invasive and non-invasive E histolytica in non-dysenteric diarrhoea. Asymptomatic subjects carried non-invasive E histolytica more frequently than invasive E histolytica. Patients with non-amoebic dysentery, when shown to be infected with E histolytica, carried non-invasive strains (12%).

CONCLUSIONS

Sensitivity and specificity of microscopical examination of a single stool specimen for diagnosing amoebic dysentery is very high; intestinal carriage of invasive E histolytica detected by culture is not necessarily an indication of active disease as patients with diarrhoea and asymptomatic subjects shed invasive and non-invasive E histolytica. There are possibly two subpopulations of invasive E histolytica with different pathogenic potential which can be differentiated by zymodeme analysis.

Entamoeba histolytica cyst passers. Clinical profile and spontaneous eradication of infection

The present study was carried out to examine whether Entamoeba histolytica cyst passers suffer from any parasite-related bowel symptoms and to assess the frequency of spontaneous eradication of this infection. The study was carried out in two parts. In part I, stool samples were collected at random from 3536 individuals living in rural communities around Delhi. E. histolytica was isolated by the culture technique in 345 (9.7%) subjects. There was no increase in the prevalence rate of bowel symptoms in the culture-positive compared to the culture-negative subjects. One hundred twenty-four (36%) of the culture-positive subjects agreed to take part in a longitudinal study; the subjects were left untreated and clinical assessment and stool examinations were carried out at three-month intervals. One hundred eighteen (95.2%) subjects had eradicated their parasite spontaneously at the end of one year; none developed any features of invasive amebiasis. Part II of the study was carried out on 625 patients attending our Gastroenterology Clinic. Positive cultures of E. histolytica were obtained from 99 (15.2%) patients. Again, there was no increase in the prevalence rate of bowel complaints in the culture-positive compared to the culture-negative subjects. Moreover, histological appearances of the rectal biopsy specimens were not significantly different between the two groups. Twenty-eight (28.2%) patients agreed to the longitudinal study and all eradicated the parasite spontaneously within five months; none developed any evidence of invasive amebiasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Non-pathogenic entamoeba histolytica in Italian HIV-infected homosexuals

A cohort of 51 homosexuals who were either HIV-positive or had AIDS was followed prospectively with parasitologic stool examination and in vitro culture in order to determine the incidence of E. histolytica infection. Amoebic isolates were further characterized by electrophoretic isoenzyme study. Five subjects (9.8%) were found to be infected with E. histolytica. None of the amoebic isolates were found to be pathogenic by isoenzyme analysis.

Chemotherapy and immunity in opportunistic parasitic infections in AIDS

Parasitic diseases are endemic in parts of the tropics, but there is no convincing evidence that their prevalence or incidence is increasing due to the HIV epidemic. Available scientific data on parasitic infections in patients with the Acquired Immunodeficiency Syndrome (AIDS) suggests a predominance of Pneumocystis carinii, Toxoplasma gondii and Cryptosporidium spp. For reasons which are unclear, parasitic infections such as Plasmodium falciparum, Strongyloides stercoralis and Entamoeba histolytica, where cell-mediated immune responses are also thought to be significant, do not appear to be opportunists of importance. It is being increasingly recognized that chemotherapy for parasitic diseases has a host-dependent component, although scientific data on this subject remain scanty. The management of opportunistic parasitic infections in patients infected with HIV is dogged by failures and relapses, aptly illustrating the notion of the relationship between chemotherapy and the immune response. This review discusses the immunity and chemotherapy of opportunistic parasite infections in patients infected with the Human Immunodeficiency Virus (HIV).

Autochthonous amoebiasis in institutionalized mentally-retarded patients: preliminary evaluation of isoenzyme patterns in three isolates

Three autochthonous cases of Entamoeba histolytica infection in institutionalized mentally-retarded patients are reported. Isoenzyme analysis by starch-gel electrophoresis shows the pathogenicity of the three isolates: two belong to zymodeme II, and one to zymodeme XIX. The study shows that invasive E. histolytica strains occur in Italy and can be isolated from institutionalized oligophrenic patients.

Factors associated with the detection of Entamoeba histolytica in homosexual men

In a study of bowel parasites in 128 Australian homosexual men attending a sexually transmitted diseases (STD) clinic, Entamoeba histolytica was detected in 37%, Giardia intestinalis in 3% and at least one protozoan in 81% of the group. There was no evidence of pathogenicity of E. histolytica, nor was there any association between the detection of E. histolytica and sexual practices, gastrointestinal symptoms, proctitis, human immunodeficiency virus antibody result or T-cell subset values. However it was noted that those subjects with an elevated IgM greater than 4 g/l were more likely to harbour E. histolytica trophozoites than those with a level below 4 g/l (OR 6.54, 95% CI 1.3-32.8). Travel to South-East Asia, India, China, Africa, South America or the Pacific islands in the previous 3 years emerged also as an independent factor (OR 2.70, 95% CI 1.12-6.53) associated with detection of E. histolytica.

Characterization of 20 Entamoeba histolytica strains isolated from patients with HIV infection

Twenty Entamoeba histolytica strains from patients with HIV-1 infection were isolated and compared with E. histolytica strains from patients without HIV infection. The isoenzyme pattern of the hexokinase as well as the hybridization with known DNA-probes were used as markers for pathogenicity. According to these markers, all 20 strains could be regarded as being nonpathogenic. Direct measurements of the virulence were carried out: destruction of monolayer tissue culture cells, capacity of phagocytosis and the ability to induce liver abscesses in the hamster. The virulence of strains from HIV patients was comparable to that of E. histolytica strains which had been isolated from HIV-negative asymptomatic carriers. In agreement with this, none of the HIV-positive patients showed symptoms of an invasive amebiasis. By PRC, no HIV-1 proviral DNA could be evidenced in the E. histolytica strains which had been isolated from HIV patients.

Opportunistic protozoan infections in human immunodeficiency virus disease: review highlighting diagnostic and therapeutic aspects

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Parasitic infections in HIV patients in Austria: first results of a long-term study

In the course of a long-term study of parasitic infections among HIV-infected persons in Austria during the period from November 1985 until May 1989, 618 persons infected with HIV (including 270 hospitalized patients, most of them with severe symptoms of AIDS) were examined. 58% of all persons had antibodies against Toxoplasma gondii. The incidence of clinically overt toxoplasmosis was about 20% in the 167 hospitalized persons infected with the parasite. In 29% of 68 patients with suspected pneumocystosis, the infection could be verified. In 9% of 219 patients, Cryptosporidium sp. was found. In two persons, an infection with Strongyloides stercoralis was diagnosed. Except these AIDS-associated opportunistic infections, the incidence of parasitic infections in the Austrian HIV-infected population was found to be low, and, except for Entamoeba histolytica, not significantly exceeding the frequency of parasitic infections in non-HIV-infected Austrians. Compared to data on the frequency of opportunistic infections in AIDS-patients in other developed countries, toxoplasmosis as well as infections with Cryptosporidium sp. seem to be more often diagnosed in Austria, whereas pneumocystosis is slightly less frequently found.

Clinical features and management of amebic liver abscess. Experience from 29 patients

29 patients with amebic liver abscess were evaluated in a study to examine clinical picture, laboratory data, epidemiology, radiologic methods, and therapy. Since the clinical picture was unspecific a considerable amount of misdiagnoses occurred, and often originated from pulmonary symptoms. To establish diagnosis one should rely on the triad with positive amebic serology, intrahepatic scanning defects, and clinical picture with fever, right upper quadrant pain, and hepatomegaly. Nearly all patients had an exposure history of travel or immigration from endemic areas in the tropics. Medical therapy with metronidazole alone is highly effective and leads to defervescence and clinical improvement usually within 3-5 days. Invasive procedures, such as needle aspiration or surgical drainage of the abscess are rarely needed; these invasive methods neither shorten the course of the disease nor improve prognosis.