A long-term follow up study of amoebiasis treated with metronidazole

Hsp90 inhibitors as new leads to target parasitic diarrheal diseases

Entamoeba histolytica and Giardia lamblia are anaerobic protozoan parasites that cause amebiasis and giardiasis, two of the most common diarrheal diseases worldwide. Current therapy relies on metronidazole, but resistance has been reported and the drug has significant adverse effects. Therefore, it is critical to search for effective, better-tolerated antiamebic and antigiardial drugs. We synthesized several examples of a recently reported class of Hsp90 inhibitors and evaluated these compounds as potential leads for antiparasitic chemotherapy. Several of these inhibitors showed strong in vitro activity against both E. histolytica and G. lamblia trophozoites. The inhibitors were rescreened to discriminate between amebicidal and giardicidal activity and general cytotoxicity toward a mammalian cell line. No mammalian cytotoxicity was found at >100 μM for 48 h for any of the inhibitors. To understand the mechanism of action, a competitive binding assay was performed using the fluorescent ATP analogue bis-ANS (4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid dipotassium salt) and recombinant E. histolytica Hsp90 preincubated in both the presence and absence of Hsp90 inhibitors. There was significant reduction in fluorescence compared to the level in the control, suggesting that E. histolytica Hsp90 is a selective target. The in vivo efficacy and safety of one Hsp90 inhibitor in a mouse model of amebic colitis and giardiasis was demonstrated by significant inhibition of parasite growth at a single oral dose of 5 mg/kg of body weight/day for 7 days and 10 mg/kg/day for 3 days. Considering the results for in vitro activity and in vivo efficacy, Hsp90 inhibitors represent a promising therapeutic option for amebiasis and giardiasis.

Amebiasis

Amebiasis is an important cause of death from parasitic disease worldwide. The causative organism is Entamoeba histolytica, which has an infective cyst stage and a pathogenic and motile trophozoite stage. The clinical presentation can vary from an asymptomatic carrier state to fulminant colitis and colonic perforation. The majority of patients can be managed medically. However, a small percentage of patients require urgent exploration and resection with an associated high mortality rate. Early recognition and initiation of medical therapy including treatment of asymptomatic carriers are vital to preventing catastrophic outcomes.

[Treatment of opportunistic infections in adolescent and adult patients infected with the human immunodeficiency virus during the era of highly active antiretroviral therapy. AIDS Study Group (GESIDA) and National AIDS Plan Expert Committee]

Despite the huge advance that highly active antiretroviral therapy has represented for the prognosis of infection by human immunodeficiency virus (HIV), opportunistic infections continue to be a cause of morbidity and mortality in HIV-infected patients. This is often the case because of severe immunodepression, poor adherence to antiretroviral therapy, failure of therapy, or the fact that patients are unaware of their HIV-positive status and debut with an opportunistic infection. This article updates the guidelines on treatment of acute episodes of various opportunistic infections in HIV-infected patients, including infections due to parasites, fungi, viruses, mycobacteria, and bacteria. This edition has a new chapter on imported parasite infections as well as additional information on endemic mycoses in the chapter on fungal infections, taking into account the growing number of immigrants in our setting. Lastly, the chapter on the immune reconstitution syndrome has also been updated, providing relevant data on a phenomenon that has clinical and diagnostic repercussions in patients who start antiretroviral therapy while they are severely immunodepressed (English version available at http://www.gesida.seimc.org).

Amoebiasis

Amoebiasis is the second leading cause of death from parasitic disease worldwide. The causative protozoan parasite, Entamoeba histolytica, is a potent pathogen. Secreting proteinases that dissolve host tissues, killing host cells on contact, and engulfing red blood cells, E histolytica trophozoites invade the intestinal mucosa, causing amoebic colitis. In some cases amoebas breach the mucosal barrier and travel through the portal circulation to the liver, where they cause abscesses consisting of a few E histolytica trophozoites surrounding dead and dying hepatocytes and liquefied cellular debris. Amoebic liver abscesses grow inexorably and, at one time, were almost always fatal, but now even large abscesses can be cured by one dose of antibiotic. Evidence that what we thought was a single species based on morphology is, in fact, two genetically distinct species--now termed Entamoeba histolytica (the pathogen) and Entamoeba dispar (a commensal)--has turned conventional wisdom about the epidemiology and diagnosis of amoebiasis upside down. New models of disease have linked E histolytica induction of intestinal inflammation and hepatocyte programmed cell death to the pathogenesis of amoebic colitis and amoebic liver abscess.

In vitro susceptibilities of Entamoeba histolytica to azithromycin, CP-63,956, erythromycin, and metronidazole

Current therapy of Entamoeba histolytica infection requires use of multiple agents effective at different body sites, including the intestinal lumen, intestinal tissue, and liver. Azithromycin and CP-63,956, new extended-half-life macrolides which reach high levels in tissue, exhibit in vitro antiamebic activity at 18 or 48 h of incubation at concentrations comparable to that of erythromycin and slightly higher than that of metronidazole. Azithromycin and CP-63,956 have the potential to be useful therapeutic agents for all types of E. histolytica infection.