protozoa 1 Flashcards
Protozoa
unicellular eukaryotes
Entamoeba histolytica
ameba that is common in the large intestine of humans. It causes amebiasis, amebic dysentery (bloody diarrhea), amebic liver abscess (dissemination- anchovy paste exudate) or abscesses in other organs. Most often it is present in asymptomatic carriers.
Entamoeba histolytica diagnosis
trophozoites (containing RBCs b/c they phagocytose them) or cysts (contain up to 4 nuclei) in stool. Also serology- antibodies against E. histolytica or detection of Gal/GalNac lectin antigen specific for E. histolytica in stool.
Entamoeba dispar
is nonpathogenic, colonizes large intestin and morphologically identical to E. histolytica, but it can be distinguished from E. histolytica by biochemical and immunological criteria.
E. histolytica vs E. dispar
Similarities: both spread through ingestion of cysts, cysts are morphologically identical, colonize large intestine. Differences: E. dispar does NOT cause invasive dz and does not elicit positive amebic serology. Distinct rRNA, surface antigens and isoenzymes. ELISA for Gal/GalNac lectin can differentiate them in stool
Life Cycle of Entamoeba histolytica
Ingest cysts > transform into trophozoites in small intestine > binary fission (90% remain in lumen and are due to E. dispar, 10% invade wall and are due to E. histolytica) > development of abscess/ extraintestinal abscesses > trophozoites and cysts released in feces
E. histolytica pathogenesis
E. histolytica attachesto mucosa via Gal/GalNac lectin producing extracellular cysteine proteases that cause tissue damage. Also lyses immune cells. Formation of flask-shaped colonic ulcers with raised edges (may heal, persist chronicaly or lead to formation of inflammatory intestinal masses called amebomas). Can disseminate and cause metastatic extraintestinal infctions.
amebic colitis clincal findings
history of immigration, gradual onset, diarrhea, heme-positive stools, abd pain, weight loss, fever >38,
amebic liver abscess findings
mostly men, hx of alcohol abuse common, fever, RUQ pain, hepatomegaly, weight loss, diarrhea, cough, elevated WBC, elevated alk phosph, elevated bilirubin, AST, ALT
E. histolytica transmission
Ingestion of cysts from contaminated food or water, or by direct personal contact. Amebiasis can also be transmitted sexually, particularly among male homosexuals. Improved sanitation and food handling procedures are important control measures.
treatment of E. histolytica
amebic colitis or liver abscess: metronidazole. Asymptomatic carrier/ luminal infection: iodoquinol
Amebas that cause CNS infections
Naegleria (primary amebic meningoencephalitis), Acanthamoeba (granulomatous amebic encephalitis and keratitis) and Balamuthia (granulomatous encephalitis). These free-living amebas are found in fresh-water or brackish habitats
Giardia lamblia
is a flagellate and is the only common pathogenic protozoan found in the duodenum or jejunum.
Giardia lamblia diagnosis
Demonstration of cysts in formed stools or cysts or trophozoites in liquid stools is diagnostic. Three or more stool examinations on alternate days is recommended. Examination of duodenal aspirates is superior to examination of stools and may be diagnostic if stool examinations are negative. Also ELISA
describe giardia trophozoites vs cysts
Tropho-zoites (10-20 mm in length) are heart shaped with two nuclei, four pairs of flagella, and a concave anteroventral sucking disk. Cysts (8-14 μm in length) are often present in stool. They are ellipsoid, thick walled, and contain 2 nuclei (immature) or 4 nuclei (mature).
Giardia lamblia life cycle
Ingested cysts excyst upon exposure to stomach acid > trophozoites undergo binary fission in duodenum and jejunum > attach to mucosa > cysts form in colon >
Giardia sx
Most asymptomatic. low-grade inflammation, crypt hypertrophy and villous flattening to villous atrophy and severe malabsorption. Giardiasis: bloating, flatulence, foul smelling fatty diarrhea
Giardiasis is life threatening in who?
pts with hypogammaglobulinemia- suggest that infection may result in partial immunity and that antibody-dependent mechanisms confer some protection against this disease
Giardiasis transmission
transmitted by ingestion of contaminated water or food or direct exposure to feces (day care centers, etc.). Waterborne outbreaks have occurred in Colorado among campers in wilderness areas and at ski resorts. Cysts can survive for several months in water. Cysts are resistant to inactivation by chlorine. Campers should subject drinking water to boiling or ultra-filtration
List the coccidia
Cryptosporidium parvum, Cryptosporidium hominis, and Cyclospora cayetanensis
Cryptosporidium sx
major cause of intractable diarrhea in patients with AIDS. In normal patients, it usually causes self-limited diarrhea
diagnosis of coccidia
Modified acid fast stain demonstrating oocysts containing 4 sporozoites. Relative cyst sizes: C. parvum is smallest, C. cayetanensis is medium, Isospora belli is largest
Life Cycle of Cryptosporidium parvum
Ingest oocysts > releases sporozoites > attach to surface of intestinal epithelium and mature asexually (schizogony) to form merozoites that can infect other intestinal cells or sexual forms develop (gametogony) and produce fertilized oocyst > mature oocyst in feces
C. parvum transmission
widespread in animals and is ususally acquired by ingestion of contaminated water. may also be transmitted by fecal-oral contact
treatment of cryptosporidiosis and cyclosporiasis
Nitazoxanide is used for treatment of cryptosporidiosis, and trimethoprim/ sulfamethoxazole is used to treat cyclosporiasis.
Trichomonas vaginalis
flagellate that causes urogenital infections
Trichomonas vaginalis diagnosis
Trophozoites in vaginal/ urethral discharge specimens by microscopic exam of wet mounts. Trophozoites are pear shaped, with four anterior flagella. Does not form cysts. Also antibody staining, culture and nucleic acid probe.
Trichomonas vaginalis life cycle
trophozoite in vagina/ urethra > multiplies by binary fission > trophozoite in vaginal and urthral secretions. The trophozoite is both the infective and diagnostic stage
trichomonas vaginalis clinical manifestations
frothy yellow or cream-colored vaginal discharge, inflammation or erosion of the infected mucosal surfaces, and local tenderness, and burning and itching. In males, the urethra, seminal vesicles and prostate may be infected. Reinfection can occur, but partial immunity may decrease severity of recurrent infections.
trichomonas vaginalis treatment
metronidazole for pt and partners
