Microbiology- Parasitology Flashcards
(41 cards)
Protozoa—gastrointestinal infections
Giardia lamblia, Entamoeba histolytica, Cryptosporidium,
Giardia lamblia
- Disease
- Transmission
- Diagnosis
- Treatment
Giardiasis—bloating, flatulence, foul-smelling, fatty diarrhea (often seen in campers/hikers)— think fat-rich Ghirardelli chocolates for fatty stools of Giardia.
Cysts in water
Multinucleated trophozoites or cysts in stool, antigen detection.
Metronidazole
Entamoeba histolytica
- Disease
- Transmission
- Diagnosis
- Treatment
Amebiasis—bloody diarrhea (dysentery), liver abscess
(“anchovy paste” exudate), RUQ pain; histology of colon biopsy shows flask-shaped ulcers.
Cysts in water
Serology, antigen testing, and/or trophozoites (with
engulfed RBCs in the cytoplasm) or cysts with up to 4 nuclei in stool.
Metronidazole; paromomycin or iodoquinol for asymptomatic cyst passers.
Cryptosporidium
- Disease
- Transmission
- Diagnosis
- Treatment
Severe diarrhea in AIDS Mild disease (watery diarrhea) in
immunocompetent hosts.
Oocysts in water
Oocysts on acid-fast stain, antigen detection.
Prevention (by filtering city water supplies); nitazoxanide in immunocompetent hosts.
Protozoa—CNS infections
Toxoplasma gondii, Naegleria fowleri, Trypanosoma
brucei,
Toxoplasma gondii
- Disease
- Transmission
- Diagnosis
- Treatment
Reactivation in AIDS brain abscesses usually seen as
multiple ring-enhancing lesions on MRI.
Cysts in meat (most common); oocysts in cat feces; crosses placenta (pregnant women should avoid cats)
Serology, biopsy (tachyzoite).
Sulfadiazine + pyrimethamine
Congenital toxoplasmosis:
classic triad of chorioretinitis, hydrocephalus, and intracranial calcifications.
Naegleria fowleri
- Disease
- Transmission
- Diagnosis
- Treatment
Rapidly fatal meningoencephalitis
Swimming in warm freshwater; enters via cribriform plate
Amoebas in CSF
Amphotericin B has been effective for a few survivors
Trypanosoma brucei
- Disease
- Transmission
- Diagnosis
- Treatment
African sleeping sickness— enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma
Tsetse fly, a painful bite
Trypomastigote in blood smear
Suramin for bloodborne disease or melarsoprol for CNS penetration.
Protozoa—hematologic infections
Plasmodium P vivax/ovale P falciparum P malariae, Babesia
Plasmodium
- Disease
Malaria—fever, headache, anemia, splenomegaly
P vivax/ovale—48-hr cycle (tertian; includes fever on first day and third day, thus fevers are actually 48 hr apart); dormant form (hypnozoite) in liver.
P falciparum—severe; irregular fever patterns; parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs.
P malariae—72-hr cycle (quartan)
Plasmodium
- Transmission
- Diagnosis
Anopheles mosquito
Blood smear: trophozoite ring form within RBC A , schizont containing merozoites; red granules (Schüffner stippling) throughout RBC cytoplasm seen with P vivax/ovale.
Plasmodium
- Treatment
Chloroquine (for sensitive species), which blocks Plasmodium heme polymerase;
if resistant, use mefloquine or atovaquone/ proguanil If life-threatening, use intravenous quinidine or artesunate (test for G6PD deficiency)
For P vivax/ovale, add primaquine for hypnozoite (test for G6PD deficiency)
Babesiosis
- Disease
- Transmission
- Diagnosis
- Treatment
fever and hemolytic anemia; predominantly in northeastern United States; asplenia risk of severe disease
Ixodes tick
Blood smear: ring form, “Maltese cross”; PCR
Atovaquone + azithromycin
Protozoa Visceral infections
Trypanosoma cruzi, Leishmania donovani
Chagas disease
- Disease
- Transmission
- Diagnosis
- Treatment
dilated cardiomyopathy with apical atrophy, megacolon,
megaesophagus; predominantly in South America
Unilateral periorbital swelling (Romaña sign) characteristic of acute stage.
Triatomine (“kissing”) bug
Trypomastigote in blood smear
Benznidazole or nifurtimox;
Leishmania donovani
- Disease
- Transmission
- Diagnosis
- Treatment
Visceral leishmaniasis (kala-azar)—spiking fevers, hepatosplenomegaly, pancytopenia. Cutaneous leishmaniasis—skin ulcers.
Sandfly
Macrophages containing amastigotes
AmphotericinB, sodium stibogluconate
Trichomonas vaginalis (protozoa)
- Disease
- Transmission
- Diagnosis
- Treatment
Vaginitis—foul-smelling, greenish discharge; itching and burning;
Sexual
Trophozoites (motile) on wet mount; “strawberry cervix”
Metronidazole for patient and partner (prophylaxis)
Nematode routes of infection
- Ingested
- Cutaneous
- Bites
EATTT: Enterobius, Ascaris, Toxocara, Trichinella, Trichuris
SANd: Strongyloides, Ancylostoma, Necator
LOW: Loa loa, Onchocerca volvulus, Wuchereria bancrofti
Enterobius vermicularis (pinworm)
- Disease
- Transmission
- Diagnosis
- Treatment
Causes anal pruritus (diagnosed by seeing
egg via the tape test).
Fecal-oral
Pyrantel pamoate or bendazoles.
Ascaris lumbricoides (giant roundworm)
- Disease
- Transmission
- Diagnosis
- Treatment
May cause obstruction at ileocecal valve, biliary obstruction, intestinal perforation, migrates from nose/mouth.
Fecal-oral; knobby-coated, oval eggs seen in feces under microscope.
Bendazoles
Strongyloides stercoralis (threadworm)
- Disease
- Transmission
- Diagnosis
- Treatment
Autoinfection: rarely, some larvae may penetrate the intestinal wall to enter the bloodstream without leaving the body.
Larvae in soil penetrate skin; rhabditiform larvae seen in
feces under microscope.
Ivermectin or bendazoles
Ancylostoma duodenale, Necator americanus (hookworms)
- Disease
- Transmission
- Treatment
Cause anemia by sucking blood from intestinal wall.
Cutaneous larva migrans—pruritic, serpiginous rash from walking barefoot on contaminated beach.
Larvae penetrate skin
Bendazoles or pyrantel pamoate
Trichinella spiralis
- Disease
- Transmission
- Treatment
Larvae enter bloodstream, encyst in striated muscle muscle inflammation.
Trichinosis—fever, vomiting, nausea, periorbital edema, myalgia
Undercooked meat (especially pork); fecal-oral (less likely).
Bendazoles
