Microbiology - MycologyParasitology

ekadar's version from 2017-01-07 19:21

Microbiology: Mycology

Systemic Mycoses

Question Answer
all causepneumonia (can disseminate)
cold meansmold
heat meansyeast


Question Answer


DiseaseEndemic location and pathological features
histoplasmosis locationMississippi, Ohio river valleys
Histo under microscopehides in macrophages (smaller than RBC)
Histo comes frombird or bat droppings in missisippi and ohio river basin
Blasto locationeast of mississippi river and central america
blasto under microscopebroad based budding
coccidiomycosis locationSouthwestern US, California. "San Joaquin Valley Fever"
coccidio under microscopespherule (much larger than RBC) filled with endospores
paracoccidio locationlatin america
paracoccidio under microscopebudding yeast with captain's wheel formation
tinea versicolorcaused by Malassezia furfur
degrades lipids and produces acids that damage melanocytes and cause hypopigmented/hyperpigmented patches
occurs in hot, humid weather
"spaghetti and meatball" appearance on KOH prep
Candida albicanscatalase positive
dimorphic (yeast with pseudohyphae in culture at 20C, germ tube formation at 37C--diagnostic)
oral and esoph thrush in immunocompr (diabetes, AIDS, neonates, steroids)
vulvovaginitis (diabetes, antibiotics use)
diaper rash
endocarditis in IV drug users
disseminated candidiasis (to any organ)
chronic mucocutaneous candidiasi
candiadal esophagitis AIDS defining lesion in 100CD4 or less
Aspergillus fumigatusInvasive - esp. in immunocompromised and those with chronic granulomatous disease
allergic bronchopulmonary aspergillosis(asthma or CF
lung cavity aspergilloma("fungus ball") - esp. after TB infxn
aflatxoinssome species of Aspergillus produce aflatoxins → hepatocellular carcinoma
appearance of aspergillus septate hyphae that branch at acute angles, not dimorphic
Cryptococcus neoformansMcc fungal meningitis
diagnosis for cryptococusstains with india ink and mucicarmine. latex agglutination test detects polysaccharide capsular antigen
appearance of cryptoyeasts with wide capsular halos and unequal budding. "soap bubble" lesions in brain.
where is cryptopigeon droppings
appearance of mucorbranching at wide angles
PCP stainsilver stain
PCP appearance on CXRdiffuse, bilateral ground glass opacities
when to start prophylaxis for PCPwhen CD4 drops below 200
sporothrixrose gardeners disease


Question Answer
Histoplasmamacrophage filled with Histoplasma (smaller than RBC)
blastomycosisbroad-base budding (same size as RBC)
coccidioidomycosisspherule filled with endospores (much larger than RBC)
paracoccidioidomycosisbudding yeast with captain's wheel formation (much larger than RBC)
Malassezia furfur"spaghetti and meatball" appearance on KOH prep
Candidapseudohyphae and budding yeasts at 20C, germ tubes at 37C
Aspergillus45 degree angle branching septate hyphae, rare budding fruit bodies
Cryptococcus5-10 um yeasts with wide capsular halo, narrow-based unequal budding
Mucorirreg board (empty-looking) nonseptate hyphae, wide-angle branching
Pneumocystissaucer-shaped yeast forms
Sporothrixcigar-shaped yeast forms, unequal budding

Treatment Summary

Question Answer
Histoplasmafluconazole or ketoconazole for supf inf, amphotericin B for systemic inf
blastomycosisfluconazole or ketoconazole for supf inf, amphotericin B for systemic inf
coccidioidomycosisfluconazole or ketoconazole for supf inf, amphotericin B for systemic inf
paracoccidioidomycosisfluconazole or ketoconazole for supf inf, amphotericin B for systemic inf
Malassezia furfurtopical miconazole, selenium sulfide (Selsun)
Candidanystatin for supf inf, amphotericin B for systemic inf
PneumocystisTMP-SMX, pentamidine, dapsone
Sporothrixitraconazole or potassium iodide
Aspergillusvoriconazole for sup inf, angioinvasive amphotericin B

Protozoa - GI and CNS infections

Question Answer
Giardia lamblia diseaseBloating
foul-smelling, fatty diarrhea
often in campers/hikers
Giardia lamblia transmissioncysts in water
Giardia lamblia dxtrophozoites or cysts (pictured here) in stool
Giardia lamblia txmetronidazole
Entamoeba histolytica diseasebloody diarrhea
liver abcess ("anchovy paste" exudate)
RUQ pain
endocytosed RBCS within trophozoite
Entamoeba histolytica transmissioncysts in water
Entamoeba histolytica dxseriology and/or trophozoites (with RBCs in the cytoplasm) or cysts (with multiple nuclei) in the stool
Entamoeba histolytica txmetronidazole or iodoquinol for asymp. cyst passers
Cryptosporidium diseasesevere diarrhea in AIDS
Mild, watery diarrhea in nonimmunocompromised
Cryptosporidium transmissioncysts in water
Cryptosporidium dxcysts on acid-fast stain
Cryptosporidium txprevention via filtering water
nitazoxanide in immunocompetent pts
Toxoplasma gondii diseasebrain abscess in HIV - ring enhancing brain lesions on CT/MRI
congenital infxn, congenital triad :Chorioretinitis, hydrocephalus, intracranial calcifications
Toxoplasma gondii transmissioncysts in meat or cat feces
crosses placenta (pregnant? trade in the cat for some folic acid)
Toxoplasma gondii dxserology, biopsy
Toxoplasma gondii txSulfadiazine + pyrimethamine. Prophalyxsis under 100 and seropositive for IgG for toxo
Naegleria fowleri diseaserapidly fatal meningoencephalitis
Naegleria fowleri transmissionswimming in freshwater lakes - enters via cribiform plate
Nalgene with fresh water containing Naegleria
Naegleria fowleri dxamoebas in spinal fluid
Naelgleria fowleri txamphotericin - but barely anyone survives
Trypanosoma brucei, gambiense, rhodesiense diseaseAfrican sleeping sickness:
-enlarged lymph nodes
-recurring fever (due to antigenic variation)
Trypanosoma brucei, gambiense, rhodesiense TransmissionTsetse fly, a painful bite
Trypanosoma brucei, gambiense, rhodesiense dxBlood smear
Trypanosoma brucei, gambiense, rhodesiense txSuramin for blood-borne disease
melarsoprol for CNS penetration

Protozoa - Hematologic & other infections

Question Answer
Plasmodium vivax/ovale, falciparum, malariae diseaseMalaria: fever, headache, anemia, splenomegaly
vivax/ovale: 48-hr cyclic fevers (tertian); dormant form in liver
falciparum: severe; irregular fevers; parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs
malariae: 72-hr cyclic fevers (quartan)
Plasmodium vivax/ovale, falciparum, malariae transmissionMosquito (Anopheles)
Plasmodium vivax/ovale, falciparum, malariae dxBlood smear, trophozoite ring form:

RBC schizont with merozoites (B):
Plasmodium vivax/ovale, falciparum, malariae tx1st: chloroquine - blocks Plasmodium heme polymerase
If resistant: mefloquine or atovaquone/proguanil for travelers
If life-threatening: IV quinidine (test for G6PD deficiency)
Vivax/ovale:add primaquine for hypnozoite (test for G6PD deficiency)
Sickle cell is protective against falciparum
can give atovaqune/proquanil for falciparum
Babesia diseasefever and hemolytic anemia
asplenic = bad disease
Babesia transmissionIxodes tick (same as Borrelia burgdorferi of Lyme disease (often a co-infxn)
Babesia dxBlood smear
Ring form (left), Maltese cross (right):

Babesia txAtovaquone + azithromycin
Trypanosoma cruzi diseaseChagas' disease:
dilated cardiomyopathy
South America
Trypanosoma cruzi transmissionReduviid bug ("kissing bug")
painless a kiss
Trypanosoma cruzi dxBlood smear:
Trypanosoma cruzi txNifurtimox
Leishmania donovani diseaseVisceral leishmaniasis (kala-azar):
spinking fevers, hepatosplenomegaly, pancytopenia
Leishmania donovani transmissionsandfly
Leishmania donovani dxmacrophages containing amastigoes:
Leishmania donovani txSodium stibogluconate
Trichomonas vaginalis disease, transmission, dx, txVaginitis - NOT the VAGINOSIS of Gardnerella vaginalis
Vaginitis = foul-smelling, greenish discharge with itching and burning
Sexually transmitted
Dx: trophozoites (motile) on wet mount
Tx: metronidazole for pt and partner

Nematodes (roundworms)

Question Answer
Enterobius vermicularis (pinworm) transmissionFood contaminated with eggs
Enterobius vermicularis (pinworm) diseaseIntestinal infxn causing anal pruritus (Scotch Tape test helps pick up eggs)
Enterobius vermicularis (pinworm) txBendazoles or pyrantel pamoate (womrs are bendy - tx with meBENDazole)
Ascaris lumbricoides (giant roundworm) transmissionFecal-oral
eggs visible in feces under microscope
Ascaris lumbricoides (giant roundworm) diseaseIntestinal infxn
Ascaris lumbricoides (giant roundworm) txBendazoles or pyrantel pamoate
Strongyloides stercoralis transmissionLarvae in soil penetrate the skin
Strongyloides stercoralis diseaseIntestinal infxn causing vomiting, diarrhea, anemia
Strongyloides stercoralis treatmentIvermectin or albendazole
Diagnosis of strongyloidesrhabditiform larvae in the stool
Ancylostoma duodenale, Necator americanus
(hookworms) transmission
Larvae penetrate skin
Ancylostoma duodenale, Necator americanus
(hookworms) disease
Intestinal infxn causing anemia by the bug sucking blood from intestinal walls
Ancylostoma duodenale, Necator americanus
(hookworms) treatment
Bendazoles or pyrantel pamoate
Dracunculus medinensis transmissionDrinking water
Dracunculus medinensis diseaseSkin inflammation and ulceration
Dracunculus medinensis txSlow extraction of worm
Onchocerca vovulus transmissionFemal blackfly bite
Onchocerca vovulus diseaseHyperpigmented skin and river blindness (black flies, black skin nodules, black sight
allergic rxn to microilaria is possible
Onchocerca vovulus txIvermectin (IVERmectin for rIVER blindness)
Loa loa transmissionDeer fly, horse fly, mango fly, zip up your fly
Loa loa diseaseSwilling in skin, worm in conjunctiva
Loa loa txDiethylcarbamazine
Wuchereria bancrofi transmissionfemale mosquito
Wuchereria bancrofi diseaseBlocks lymphatic vessels:
takes 9 months - 1 yr after bite to become symptomatic
Wuchereria bancrofi txDiethylcarbamazine
Toxocara canis transmissionFood contaminated with eggs
Toxocara canis diseaseVisceral larva migrans
Toxocara canis txAlbendazole or mebendazole
Nematode routes of infectionYou'll get sick if you EAT these! (Enterobius, Ascaris, Trichinella
There get into your feet from the SANd. (Cutaneous - Strongyloides, Ancylostoma, Necator)

Nemotode Routes of infection

Question Answer
ingestedthink EATT (Enterobius, Ascaris, Toxocara, Trichinella)
cutaneousthink SANd (Strongyloides, Ancylostoma, Necator)
bitesthink lay LOW (Loa loa, Onchocerca volvulus, Wuchereria bancrofti)

Cestodes (tapeworms) and Trematodes (flukes) [all: transmission, disease and treatment]

Question Answer
Taenia soliumCestodes (tapeworm)
Ingestion of larvae encysted in undercooked pork or eggs
pork → intestinal infx
eggs → Cysticercosis, neurocysticercosis
tx: Praziquantel; bendazoles for neurocysticercosis
Diphyllobothrium latumCestodes (tapeworm)
Ingestion of larvae from raw freshwater fish
Vitamin B12 deficiency (tapeworm competes for B12 in intestine) → anemia
tx: praziquantel
Echinococcus granulosusCestodes (tapeworm)
Ingestion of eggs from dog feces
Cysts in liver, causing anaphylaxis if antigens are released (surgeons preinject the cyst with ethanol to kill cysts before removal)
tx: bendazoles
SchistosomaTrematodes (fluke)
snales are host; cercariae penetrate skin of humans
Liver and spleen granulomas, fibrosis and inflammation
Chronic infxn (S. haematobium) - squamous cell carcinoma of the bladder
tx: Praziquantel
Clonorchis sinensisTrematodes (fluke)
Undercooked fish
Biliary tract inflammation → pigmented gallstones
tx: Praziquantel
Paragonimus westermaniTrematodes (fluke)
Undercooked crab meat
Lung inflammation and 2° bacterial infxn with hemoptysis
tx: Praziquantel

Parasite hints

biliary tract disease, cholangiocarcinomaclonorchis
brain cyststaenia solium (cysticerocisis)
hematuria, squamous cell bladder cancerschistosoma haematobium
liver (hydatid cysts)echinococcus
microcytic anemiaancylostoma, necator
myalgias, periorbital edematrichinella spiralis
periana, pruritusenterobius
portal hypertensionschistosoma mansoni
B12 deficiencydiphyllobothrium latum