Microbiology
Summary
Entamoeba histolytica is an intestinal protozoan responsible for the disease known as amebiasis. This parasite forms infectious cysts which are shed in the stool and serve as a primary mode of transmission. Humans become infected by consuming food or water contaminated with these cysts. Additionally, amebiasis can be transmitted sexually through anal-oral contact.
Once inside the body, the parasite can cause hepatic amebiasis. Such infections typically result in amebic liver abscesses that are characterized by their unique "anchovy paste" consistency and can lead to right upper quadrant pain. In the intestines, amebiasis manifests as ulcerations in the mucosa, leading to symptoms like bloody diarrhea. Microscopically, these ulcers exhibit a flask-shaped appearance. Diagnosis of the infection is commonly achieved via a stool O&P examination, where the presence of E. histolytica trophozoites with ingested red blood cells is pathognomonic for amebiasis. Treatment typically involves the use of metronidazole, with paromomycin and iodoquinol being luminal agents employed to eradicate intestinal cysts.
Lesson Outline
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FAQs
E. histolytica is a protozoan parasite that causes infections in humans, most notably amebiasis. It primarily resides in the human intestines and can lead to conditions such as intestinal amoebiasis and amoebic liver abscesses. If left untreated, it can be severe and potentially fatal.
Common symptoms of an E. histolytica infection can range from mild stomach discomfort to more severe symptoms such as bloody diarrhea, a classic sign of amebiasis. In more extreme cases, like amoebic liver abscesses, symptoms could include fever, right upper stomach pain, and weight loss.
Diagnosis of E. histolytica infection often involves laboratory testing of stool samples (also known as a stool O&P, or ova and parasites test). The presence of trophozoites (a stage in the parasite's life cycle) with endocytosed red blood cells in the stool are strong indicators of infection.
The primary treatment for E. histolytica infection typically relies on prescription medications. Currently, the most common treatment is a drug called metronidazole, often used in conjunction with paromomycin or iodoquinol, especially in severe cases such as amoebic liver abscesses. Physicians might recommend additional medications to manage symptoms and complications.
