medically important fungi
DESCRIPTION
Flash CardsTRANSCRIPT
USMLE Step 1 Flash Cards
Dimorphic Fungi Blastomyces
Histoplasma
Coccidioides
Sporothrix
Body Heat Changes Shape for the dimorphic fungi
Pseudohyphae (Candida albicans)
• Hyphae with constrictions at each septum
Spore types
Conidia
Asexual spores; formed off hyphae; common; air-borne
Blastoconidia
“Buds” on yeasts (asexual budding daughter yeast cells)
Arthroconidia
Asexual spores formed by a “joint”
Spherules and Endospores (Coccidioides)
Spores inside the spherules in tissues
Malassezia furfur
Normal skin flora (lipophilic yeast)
Patient with blotchy hypo-pigmentation of skin
KOH scrapping shows “spaghetti and meatballs” or
“bacon and eggs” yeast clusters & short curved septate
hyphae
Treatment :
Topical selenium sulfide; recurs
Dermatophytes (group of fungi) Filamentous (monomorphic) fungi
Three genera:
Trichophyton – skin, hair and nails
Mircrosporum – hair and skin
Epidermophyton – skin and nails
Patient with scaly, ringlike lesions (Tineas) of skin. May involve hair shaft or
nails.
KOH scrapping shows athroconidia and hyphae
Treatment :
Topical imidazole or tolnafate
ID reaction (dermatophytID) = allergic response to circulating fungal antigens.
Sporothrix schenckii
Subcutaneous mycoses
Patient with subcutaneous/lymphocutaneous
mycetoma
Gardener, florist, basket weaver, or alcoholic rose-
garden sleeper disease (homeless)
Cigar-shaped yeast in pus
Treatment : intraconazole or amphotericin B
Histoplasma capsulatum
Deep fungal infection; dimorphic fungi
Normal patient with acute pulmonary; IC patient with chronic
pulmonary or disseminated infection (FUNGUS FLU)
States following drainages of Great Lakes to Gulf of Mexico
Exposure to bird or bat excrement
Sputum or blood cultures with mononuclear cells packed with
yeast cells (tiny yeast inside macrophages)
Treatment : Ketoconazole, amphotericin B
Coccidioides immitis Deep fungal infection; dimorphic fungi
Normal patient with erythema nodosum or self-resolving
pneumonia
IC patient with calcifying chronic pulmonary or disseminated
infections
Pregnant female in 3rd trimester, disseminated infection
Desert southwest
Sputum has spherules with endospores
Treatment : Amphotericin B
Blastomyces dermatitidis Deep fungal infection; dimorphic fungi
Normal patient with acute pulmonary symptoms
IC patient with chronic pulmonary or disseminated infection
North and South Carolina (otherwise coexists with
Histoplasma)
Sputum has broad-based, budding yeasts with double,
refractile cell walls.
Treatment : Amphotericin B
Aspergillus fumigatus Monomorphic filamentous OPPORTUNISTIC fungi
Patient with asthma allergies – growing mucous plugs in
lung
Patient with cavitary lung lesions – fungus ball
Patient with burns – cellulitis, invasion
IC patient – pneumonia, meningitis
Septate hyphae branch at acute angles
Treatment : Itraconazole or Amphotericin B
Candida albicans OPPORTUNISTIC fungi
Forms germ tubes at 37˚C; pseudohyphae & true hyphae when invades
tissues
Germ tube test demonstrates pseudohyphae and hyphae
IC patient, overuse of antibiotics – thrush, spread down GIT,
septicemia
IV drug abusers - endocarditis
Treatment :
topical or oral imidazoles; nystatin
Disseminated : Amphotericin B or fluconazole
Cryptococcus neoformans
Encapsulated (monomorphic) yeast;
OPPORTUNISTIC fungi
Pigeon breeder with acute pulmonary symptoms
Hodgkins/AIDS patient with meningitis
India Ink mount of CSF with encapsulated yeasts
Treatment : Amphotericin B + flucytosine until
afebrile (minumum 10 wks), then fluconazole
Mucor, Rhizopus, Absidia Ketoacidotic diabetic or leukemic patient with
rhinocerebral infection
Biopsy with non-septate irregular-width hyphae
branching at 90˚ angles.
Treatment :
High fatality rate (rapid growth and invasion)
Debride necrotic tissue & start Amphotericin B fast.
Pneumocystis jiroveci Obligate extracellular parasite
Premature infant or AIDS patient with atypical pneumonia
Biopsy with honeycomb exudates and silver-staining cysts
X-ray ground glass
Treatment :
TMP-SMX for mild
Dapsone for moderate to severe