Mycology Flashcards
Microsporum
Dermatophyte
Infects skin and hair, rarely nails
Macroconidia are large, spindle or cylinder shaped, thick walled, multi septate, rough, and spiny
Macroconidia are born singly on short conidiophores
Microconidia are few to absent and are small and club shaped
Ectothrix hair invasion, some species cause hair to fluoresce
Most common species are M. caris, M. gypseum, and M. audouinii
Tricophyton
Dermatophyte
Infects skin, hair, and nails
Macroconidia are rare, pencil shaped, multi septate, thin walled, smooth, born singly on conidiophore
Microconidia are more predominant, spherical, tear shaped, or clavate (club shaped)
Endothrix and ectothrix infections of hair but doesn’t usually fluoresce
May have spirals, nodular bodies, chlamydospores, faviform mycelia
T. rubrum colonies are red on reverse side
Most common species are T. mentagrophytes, T. rubrum, and T. tonsurans (primary cause of tinea capitis in US)
Epidermophyton
Dermatophyte
Infects skin, sometimes nails, rarely hair
Macroconidia are club shaped, septate, thin walled, and smooth
Born in singles or clusters of 2-3 on conidiophore
No microconidia
Have numerous chlamydospores
E. floccosum is the only species
Bastomyces dermatitidis
Dimorphic fungi
North American blastomycosis (Gilchrist’s disease)
Mold phase is white to gray-brown colonies
Hyaline, septate hyphae with small oval conidia born singly at tips of conidiophores
Resemble lollipops
Yeast phase is round and thick walled
Single buds connected by a wide neck
Endemic to Ohio and Mississippi River valleys
Usually in farmers who contact it from the soil
Begins in the lungs and may become systemic
Paracoccidioides brasiliensis
Dimorphic fungi
South American blastomycosis
Most phase resembles blastomyces
Yeast phase is round and double walled, multiple buds pinched as attachment
Resembles a “mariners wheel”
Mainly in Brazil (duh), Argentina, S. Mexico
Begins in lungs and may become systemic
Coccidioides immitis
Dimorphic fungi
Valley fever
Mold phase is fluffy or powdery white to gray-tan colonies and barrel-shaped arthrospores
Yeast phase is spherical containing numerous endospores
Found in desert of Southwest US
More common in dark-skinned men
Spores are inhaled or contaminate injured skin
Affects respiratory tract first, can spread to other organs
Arthrospores are highly infectious
Histoplasma capsulatum
Dimorphic fungi
Histoplasmosis (spelunker’s disease, Darling’s disease)
Mold phase is silky, white to gray-tan colonies with thick-walled spherical macroconidia surrounded by finger-like projections (“Tuberculate chlamydospores”)
Yeast phase is round to oval, intracellular in phagocytes of blood or bone marrow
Endemic in Ohio and Mississippi River valleys
Soil saprophyte found in manure of chickens, pigeons, and bats
Causes acute pulmonary disease that can be self-limited or spread
Tissue phase may be confused with Leishmania
Sporothrix schenckii
Dimorphic fungi
Sporotrichosis (rose gardener’s disease)
Mold phase is white to yellow colonies with clusters of pear-shaped conidia at tips of conidiophores (look like flowers)
Yeast phase is Gram positive and cigar shaped cells that are not usually seen in direct smears unless by immunofluorescence
Found in Mississippi and Missouri River valleys
Found on rose bushes, barberry bushes, sphagnum moss, and mulch
Usually infects farmers or florists
Introduced by trauma, usually to the hand
Cutaneous lesions spread along lymphatics
Candida albicans
Yeast
Causes thrush, vulvovaginitis, diaper rash, onychomycosis (nails), paronychomycosis (cuticles), endocarditis, meningitis, UTI, pulmonary infections, and fungemia
Grows on SBA, EMB (spider-like projections), and SDA
Gram positive cells with blastoconidia or pseudohyphae
Produces germ tubes in serum with round terminal chlamydospores on cornmeal agar
Most frequently isolated yeast
Normal flora in the GI tract and mucocutaneous areas
Serious infections most often in immunocompromised patients
Onychomycosis and esophagitis is common in patients with AIDS
Candida tropicalis
Yeast
Causes vaginitis, UTI, GI, pulmonary, and systemic infections
Blastoconidia produces randomly along pseudohyphae on cornmeal agar
May produce constricted germ tubes (true germ tubes lack constrictions)
Usually affects the immunosuppressed
Geotrichum candidum
Yeast
Uncommon cause of wound infections and oral thrush
Forms hockey stick shaped arthroconidia on cornmeal agar
No blastoconidia
Cryptococcus neoformans
Yeast
Causes lung infections that can disseminate to the brain
Irregularly sized, spherical cells surrounded by a capsule
Maroon to brown-black colonies on niger seed agar
Urease positive and phenol oxidase positive
Found in bird and bat droppings, decaying vegetation, fruit, and milk
Capsule seen with India ink prep in about 50% of cases
Cryptococcal antigen test preferred and performed on CSF
Disseminated cryptococcosis common in AIDS patients (causing cryptococcal meningitis)
Malassezia furfur
Yeast
Causes tinea versicolor and systemic infections in children given lipid replacement therapy
Oval or bottle-shaped budding yeast with characteristic collar between mother and daughter cells
Chains of short, slightly curved septate hyphae may be seen in skin scrapings
Usually not cultured in skin infections
Identified from KOH prep of skin scrapings
Characteristic “spaghetti and meatballs” appearance
In systemic infections, recovered from blood cultures
Will only grow on media overlaid with fatty acids (mineral oil or olive oil)
Pneumocystis jiroveci
Yeast
Causes atypical interstitial plasma cell pneumonia (PCP)
Cysts are spheres with intracystic bodies (looks like parentheses under the scope)
Can’t be cultured
Diagnosed by histopathological staining
Opportunistic infection in AIDS and other immunocompromised patients
Formerly P. carinii and classified as a protozoan
Rhizopus
Opportunistic fungi and common laboratory contaminant
Classified as a zygomycetes
Has a propensity to attack the vascular system of immunocompromised patients
Is rapidly spreading and often fatal
Colonies are mature within four days and are “lid lifters” meaning they grow so fast and have high aerial mycelium that push the lid up
Front is dense cotton-candy like growth, white at first, then turning gray or yellowish brown
Reverse stays white
Hyphae are large, broad, and nonseptate
Produces horizontal stolons that attach by rhizoids
Sporangiophores in clusters opposite rhizoids
Terminate in dark, round sporangia containing sporangiospores
