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Fungi & Parasites USMLE STEP 1
from First Aid
Terms in this set (41)
histoplasmosis, blastomycosis, coccidiomycosis, paracoccidiomycosis. All can cause pneumonia and disseminate. All are caused by dimorphic fungi (cold=mold, heat=yeast) except for coccidiomycosesis which is a spherule (not yeast) in tissues. Treatment=fluconazole or itraconazole for local infection; amphotericin B for systemic infection. systemic mycoses can mimic tb w/granuloma formulation but there is NO person-person transmission
mississippi and Ohio river valleys. Causes pneumonia. Macrophage filled w/histoplasma (smaller than RBC). Found in bird or bat droppings
states east of mississippi river and central america. Causes inflammatory lung dz and can disseminate to skin and bone. Forms granulomatous nodules. Broad based budding. Same size as RBCs.
SW US, california. Causes pneumonia and meningitis, can disseminate to bone and skin. Case rate increases after earthquakes (spores in dust are thrown up in the air and become spherules in lungs). Spherule filled w/endospores (much larger than rbcs). San joaquin valley or desert/desert bumps/"valley fever"
Latin america. Budding yeast w/"captains wheel" formation (much larger than RBC).
caused by malassezia furfur. Degradation of lipids produces acids that damage melanocytes and cause hypopigmented or hyperpigmented patches. Occur in hot, humid weather. Treatment=topical miconazole, selenium sulfide. "spaghetti and meatball appearance" on KOH prep.
systemic or superficial fungal infection. Oral and esophageal thrush in immunoocompromised (neonates, steroids, diabetes, AIDs), vulvovaginitis (diabetes, use of abx), diaper rash, endocarditis in IV drug users, disseminated candidiasis (to any organ), chronic mucocutaneous candidiasis. Tx=topical azole for vaginal, fluconazole or caspofungin for oral/esophageal, fluconazole, amphotericin B, or caspofungin for systemic
invasive aspergillosis, esp in immunocompromised and those w/chronic granulomatous dz. Allergic bronchopulmonary aspergillosis w/asthma or CF, aspergillomas in lung cavities esp after TB infection. Some species of aspergillosis produce aflatoxins which are ass'd with HCC. Acute Angles. Not dimorphic
cryptococcal meningitis, cryptococcosis. Heavily encapsulated yeast. Not dimorphic. Found in soil, pigeon droppings. Acq'd through inhalation w/hematogenous dissemination to meninges. Culture on sabourad's agar. Stains w/india ink. Latex agglutination test detects polysaccharide capsular antigen and is more specific. "soap bubble" lesions in brain
Mucor and rhizopus spp
mucormycosis. Dz usually mostly in ketoacidotic diabetic and leukemic pts. Fungi proliferate in blood vessel walls when there is excess ketone and glucose, penetrate cribiform plate, and enter brain. Rhinocerebral, frontal lobe abscesses. Headache, facial pain, black necrotic eschar on face, may have cranial nerve involvement
causes pneumocystis pneumonia, a diffuse interstitial pneumonia. Yeast (originally classified as protozoan). Inhaled. Most infections are asymptomatic. Immunosuppression predisposes to dz. Diffuse, bilateral CXR appearance. Diagnosed by lung biopsy or lavage. disc shaped yeast forms on methamine silver stain of lung tissue. treatment=tmp=smx,pentamidine, dapsone. start prophylaxis when CD4<200.
sporotrichosis. Dimorphic, cigar shaped budding yeast that lives on vegetation. Spores traumatically introduced to skin, typically by a thorn. "rose gardener's dz". Causes local pustule or ulcer w/nodules along draining lymphatics (ascending lymphangitis). little systemic illness. treatment=intraconazole or potassium iodide
giardiasis:bloating, flatulence, foul-smelling fatty diarrhea. Campers/hikers. Transmission through cysts in h2o. Diagnosis=trophozoites or cysts in stool. Tx=metronidazole
amebiasis: bloody diarrhea (dysentery), liver abscess ("anchovy paste" exudate), RUQ pain (Histology shows flask shaped ulcer if submucosal abscess of colon ruptures). Transmission via cysts in h2o. Diagnosis by serology and/or trophozoites (w/RBCs in cytoplasm) or cysts (w/multiple nuclei) in stool. tx=metronidazole, iodoquinol for asymptomatic cyst passers
severe diarrhea in AIDs. Mild dz (watery diarrhea) in nonimmunocompromised. Transmission via cysts in h2o. Diagnosis by cysts on acid fast stain. Tx=prevention (water supplies ), nitazoxanide in immunocompromised hosts
brain abscess in HIV (ring enhancing lesion); congenital toxoplasmosis=triad of chorioretinitis, hydrocephalus, and intracranial calcifications. Transmission through cysts in meat or cat feces. Crosses placenta. Diagnosis through serology and biopsy. Tx=sulfadiazine + pyrimethamine
rapidly fatal meningoencephalitis. Transmission through swimming in fresh h2o lakes-->enters via cribiform plate. Diagnosis by amoebas in spinal fluid. Amphotericin has been effective for a few survivors
Trypansoma :brucei, gambiense, rhodiense
African sleeping sickness. Enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma. Transmitted by painful bite of tsetse fly. Diagnosed on blood smear. Tx=suramin for blood borne dz or melarsopol for CNS penetration
Plasmodium vivax and ovale
48 hour cycle (tertian-fever on 1st day and 3rd day). Dominant form=hypnozoite in liver. Transmitted by anopheles mosquito. Diagnosed on blood smear by trophozoite ring form or rbc schizont w/merozoites. Tx begun w/chloroquine which blocks Plasmodium heme polymerase. if resistant use mefloquine. if life threatening, use iv quinidine (check for G6PD deficiency). for vivax/ovale, must add primaquine for hypnozoite (test for G6PD deficiency!!)
severe, irregular fever patterns, parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs. Transmitted by anopheles mosquito. Blood smear show trophozoite ring form, RBC schizont w/merozoites
72 hour cycle (quartan). Transmitted by anopheles mosquito. Diagnosed on blood smear by trophozoite ring form, RBC schizont w/merozoites
Treatment for malaria
begin w/chloroquine which blocks plasmodium heme polymerase, if resistant, use mefloquine. If lifethreatening, use IV quinidine (test for G6PD deficiency!). For vivax/ovale add primaquine for hypnozoite form (test for G6PD deficiency!)
Babesiosis=fever and hemolytic anemia, predominantly in Northeastern US, asplenia incr risk of severe dz. Transmission via Ixodes tick, same vector as lyme disease. May often coinfect humans. Diagnose on blood smear "Maltese cross" or PCR. Tx=atovaquone + Azithromycin.
Chagas' dz: dilated cardiomyopathy, megacolon, megaesophagus. Predominantly in S America. Transmitted by painless bite of reduviid/"kissing" bug. Diagnosed on blood smear. Tx=nifurtimox
Visceral leishmaniasis=kala-azar: spiking fevers, hepatosplenomegaly, pancytopenia. Transmitted by sandfly. Diagnosed by macrophages containing amastigotes. Tx=sodium stibogluconate
Vaginitis: foul smelling, greenish discharge, itching and burning. STI b/c cannot exist outside of humans b/c cannot form cysts. Diagnose by trophozooites (motile) on wet mount. Tx=metronidazole for pt and partner (prophylaxis)
pinworm. Transmitted in food contaminated with eggs. Intestinal infection causing anal pruritus. Diagnosed via scotch tape test. Tx=bendazoles or pyrantal pamoate
giant roundworm. Fecal-oral. Eggs visible in feces under microscope. Intestinal infection. Tx=bendazole or pyrantel pamoate
transmitted via larvae in soil that penetrate skin. Intestinal infection causing anemia by sucking blood from intestinal walls. Tx=bendazoles or pyrantel pamoate
transmitted in drinking water. Causes skin inflammation and ulceration. Tx=slow extraction of worm
transmitted by female blackfly bite. Causes hyperpigmented skin and river blindness. Allergic rxn to microfilaria possible. Tx=ivermectin
transmitted via horse/deer/mango fly. Causes swelling in skin, worm in conjunctiva. Tx=diethylcarbamazine.
transmitted via food contam w/eggs. Causes visceral larval migrans. Tx=albendazole or mebendazole
Enterobius Ascaris Trichinella
Strongyloides Ancylostoma Necatur
transmitted via ingestion of larvae encysted in undercooked pork or ingestion of eggs. Can cause intestinal infection, cysticercosis, neurocysticercosis. Tx=praziquantel,bendazoles (for neurocysticercosis)
transmitted via ingestion of larvae from raw freshwater fish. Causes vitamin B12 deficiency (competition)->anemia. Tx=praziquantel
transmitted via ingestion of eggs from dog feces. Cysts in liver causing anaphylaxis if antigens released. Preinject w/ethanol to kill cysts before removal. Treat with -bendazoles
snails are hosts, carcariae penetrate skin of host. Cause liver and spleen granulomas, fiberosis, and inflammation. Chronic infection w/s. haemotobium can lead to squamous cell cancer of the bladder. Treat w/praziquantel
transmitted via undercooked fish. Causes biliary tract inflammation->pigmented gallstones. Ass'd w/cholangiocarcinoma.. Tx=praziquantel
transmitted via undercooked crab meat. Causes lung inflammation and 2ary bacterial infection w/hemoptysis. Tx=praziquantel
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