micro: protozoa

Question 1

entamoaba histolytica

Answer 1

-> amebiasis: bloody diarrhea (dysentery), liver abscess (anchovy-paste exudate), RUQ pain, histology shows flask-shaped ulcer. transmission: cysts in water. Dx: serology and/or trophozoites (w/RBCs in cytoplasm) or cysts (up to 4 nuclei) in stool. Tx: flagyl; iodoquinol for ASx cyst passers

Question 2

cryptosporidium

Answer 2

-> severe diarrhea in AIDS. mild dz in immunocompetent. transmission: oocysts in water. Dx: oocysts on acid-fast stain. PPx: filter city water; nitazoxanide for immunocompetent hosts

Question 3

toxoplasma

Answer 3

congenital: classic triad: chorioretinitis, hydrocephalus, intracranial calcifications; reactivation in AIDS -> brain abscess = ring-enhancing lesions. transmission: cysts in meat, cat feces, crosses placenta. Dx: serology, Bx: tachyzoite. Tx: sulfadiazine + pyrimethamine

Question 4

naegleria fowleri

Answer 4

-> rapidly fatal meningoencephalitis. transmission: swimming in freshwater lakes (think nalgene), enters via cribriform plate. Dx: amoebas in spinal fluid. Tx: ampho B (most die).

Question 5

trypanosoma brucei

Answer 5

-> african sleeping sickness: LAD, recurring fever, somnolence, coma. transmission: tsetse fly: painful bite. Dx: blood smear. Tx: suramin for blood-borne, melarsoprol for CNS penetration. “it sure is nice when melatonin helps me sleep.”

Question 6

plasmodium

Answer 6

-> malaria: fever, h/a, anemia, splenomegaly. transmission: anopheles mosquito. Dx: blood smear: trophozoite ring form w/in RBC, schizont containing merozoites. Tx: chloroquine (blocks plasmodium heme polymerase). if resistant, use mefloquine or atovaquone/proguanil. if life-threatening, IV quinidine or artesunate (test for G6PD first).

Question 7

P. vivax/ovale

Answer 7

48hr cycle (tertian; includes fever on 1st and 3rd days (48 hrs apart)), dormant form (hypnozoite) in liver so add Tx w/primaquine after testing for G6PD.
red granules (schuffner stippling) throughout RBC

Question 8

P. falciparum

Answer 8

-> severe, irregular fever patterns; parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs

Question 9

P. malariae

Answer 9

72hr cycle (quartan)

Question 10

babesia

Answer 10

-> fever + hemolytic anemia, predominantly in NE US; asplenia -> inc. risk of dz. transmission: ixodes tick (same as borrelia), may often coinfect humans. Dx: blood smear: ring form, maltese cross, PCR. Tx: atovaquone + azithro

Question 11

trypanosoma cruzi

Answer 11

chagas dz: dilated CM w/apical atrophy, megacolon, mesaesophagus, predominantly in SA. unilateral periorbital swelling (romana sign) characteristic of acute stage. transmission: reduviid bug = kissing bug feces, deposited in a painless bite. Dx: blood smear. Tx: benznidazole or nifurtimox

Question 12

leishmania

Answer 12

-> visceral leishmaniasis (kala-azar): spiking fevers, HSM, pancytopenia. transmission: sandfly. Dx: macrophages containing amastigotes. Tx: ampho B, NA stibogluconate

Question 13

trichomonas

Answer 13

cannot exist outside human b/c it cannot form cysts.