protozoa 1

Question 1

Protozoa

Answer 1

unicellular eukaryotes

Question 2

Entamoeba histolytica

Answer 2

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.

Question 3

Entamoeba histolytica diagnosis

Answer 3

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.

Question 4

Entamoeba dispar

Answer 4

is nonpathogenic, colonizes large intestin and morphologically identical to E. histolytica, but it can be distinguished from E. histolytica by biochemical and immunological criteria.

Question 5

E. histolytica vs E. dispar

Answer 5

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

Question 6

Life Cycle of Entamoeba histolytica

Answer 6

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

Question 7

E. histolytica pathogenesis

Answer 7

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.

Question 8

amebic colitis clincal findings

Answer 8

history of immigration, gradual onset, diarrhea, heme-positive stools, abd pain, weight loss, fever >38,

Question 9

amebic liver abscess findings

Answer 9

mostly men, hx of alcohol abuse common, fever, RUQ pain, hepatomegaly, weight loss, diarrhea, cough, elevated WBC, elevated alk phosph, elevated bilirubin, AST, ALT

Question 10

E. histolytica transmission

Answer 10

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.

Question 11

treatment of E. histolytica

Answer 11

amebic colitis or liver abscess: metronidazole. Asymptomatic carrier/ luminal infection: iodoquinol

Question 12

Amebas that cause CNS infections

Answer 12

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

Question 13

Giardia lamblia

Answer 13

is a flagellate and is the only common pathogenic protozoan found in the duodenum or jejunum.

Question 14

Giardia lamblia diagnosis

Answer 14

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

Question 15

describe giardia trophozoites vs cysts

Answer 15

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).

Question 16

Giardia lamblia life cycle

Answer 16

Ingested cysts excyst upon exposure to stomach acid > trophozoites undergo binary fission in duodenum and jejunum > attach to mucosa > cysts form in colon >

Question 17

Giardia sx

Answer 17

Most asymptomatic. low-grade inflammation, crypt hypertrophy and villous flattening to villous atrophy and severe malabsorption. Giardiasis: bloating, flatulence, foul smelling fatty diarrhea

Question 18

Giardiasis is life threatening in who?

Answer 18

pts with hypogammaglobulinemia- suggest that infection may result in partial immunity and that antibody-dependent mechanisms confer some protection against this disease

Question 19

Giardiasis transmission

Answer 19

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

Question 20

List the coccidia

Answer 20

Cryptosporidium parvum, Cryptosporidium hominis, and Cyclospora cayetanensis

Question 21

Cryptosporidium sx

Answer 21

major cause of intractable diarrhea in patients with AIDS. In normal patients, it usually causes self-limited diarrhea

Question 22

diagnosis of coccidia

Answer 22

Modified acid fast stain demonstrating oocysts containing 4 sporozoites. Relative cyst sizes: C. parvum is smallest, C. cayetanensis is medium, Isospora belli is largest

Question 23

Life Cycle of Cryptosporidium parvum

Answer 23

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

Question 24

C. parvum transmission

Answer 24

widespread in animals and is ususally acquired by ingestion of contaminated water. may also be transmitted by fecal-oral contact

Question 25

treatment of cryptosporidiosis and cyclosporiasis

Answer 25

Nitazoxanide is used for treatment of cryptosporidiosis, and trimethoprim/ sulfamethoxazole is used to treat cyclosporiasis.

Question 26

Trichomonas vaginalis

Answer 26

flagellate that causes urogenital infections

Question 27

Trichomonas vaginalis diagnosis

Answer 27

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.

Question 28

Trichomonas vaginalis life cycle

Answer 28

trophozoite in vagina/ urethra > multiplies by binary fission > trophozoite in vaginal and urthral secretions. The trophozoite is both the infective and diagnostic stage

Question 29

trichomonas vaginalis clinical manifestations

Answer 29

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.

Question 30

trichomonas vaginalis treatment

Answer 30

metronidazole for pt and partners