Fungi Flashcards
limited to the outermost layers of hair/skin
mild infections with no/minimal inflammation
diagnosed with wet mount of hair/skin with 10% KOH
superficial mycoses
superficial mycosis
hard, gritty brown/black concretions on scalp hair
shave hair, will not recur
black piedra
Piedra hortae
superficial mycosis
Soft, white granules on hair shafts of genital and beard areas
Shave hair, will not recur
white piedra
Trichosporon beigelii
superficial mycosis
Brown/black macules on palms > soles
Topical keratolytic agent or azole
Tinea nigra
Exophiala werneckii
superficial mycosis
Hyper- and hypo-pigmented confluent scaly macules on torso
Selenium sulfide solution/keratolytic agent, topical azole for recurrence
Diagnosis requires oil supplementation in culture
Tinea/pityriasis versicolor
Malassezia furfur
Infect keratinized tissues (epidermis, hair, nails) may elicit cellular immune response Tinea capitis (head); tinea barbae (beard); tinea corporis (body); tinea cruris (perineum = jock itch); tinea pedis (feet = athletes foot); tinea unguium (nails)
dermatophytes: Microsporum, Trichophyton, Epidermophyton
diganosis: Wet mount in 10% KOH – skin, hair, nail scraping
Culture inmedia with cyclohexamide and chloramphenicol (inhibit bacteria)
treatment is oral or topical antifungal
Cutaneous Mycoses
Usually involves trauma for entry
Some infections may not respond to antifungals and require surgery
Subcutaneous mycoses
subcutaneous mycosis
Dimorphic fungus implanted into skin by trauma
Nodule at site of entry ulcerates and forms other nodules along lymphatics
Dx: culture, white mold will darken to brown/black with prolonged incubation at 25 degrees; cigar shaped yeasts on biopsy
Rx: antifungal
Lymphocutaneous sprortrichosis
Sporothrix schenckii
subcutaneous mycosis
Warty, vegetative, cauliflower-like lesions
Dx: histopathology with epithelial cell hyperplasia and cooper colored spherical fungi in sclerotic or Medlar bodies
Rx: surgical excision, cryosurgery, antifungals
Chromoblastomycosis
Fonsecaea or Cladosporium spp.
subcutaneous mycosis
Similar to mycetoma caused by Actinomycetes
Purulent drainage from sinus tracts
Dx: histopathology of grains or sulfur granules from sinus tracts showing fungal elements; culture
Rx: surgical excision or amputation for extensive disease, wide margins to prevent recurrence; limited success with antifungals
Eumycotic mycetoma
Pseudallescheria boydii
Madurella grisea
Dimorphic fungi, can affect healthy hosts, often have geographic predilection
Inhaled and may cause chronic lung infection similar to TB
May cause systemic or disseminated disease in the immunocompromised
primary fungal pathogens that cause deep tissue infections
primary fungal pathogens that cause deep tissue infections
Mostly seen in the Eastern and Midwest US
Inhaled spores enter the lung and cause primary lung infection that may not be apparent
Chronic pneumonia and cavity
Dissemination to skin, bone and GU tract
Broad base budding yeast within microabscesses and granulomas
Rx: antifungals
Blastomycosis
Blastomyces dermatitidis
primary fungal pathogens that cause deep tissue infections
Mostly seen in SW US and Mexico
Inhaled spores enter lung:
Symptomatic ling infection in 40%
Chronic lung infection may cause lung cavity
Dissemination to CNS, bone, skin
Predispositions for dissemination: AIDS, dark-skin, pregnancy
Dx: culture (can be acquired via lab handling), biopsy, complement fixation Ab for disseminated disease and relapse
Endospores within spherules seen in pyogenic and granulomatous reaction
Rx: antifungals
Coccidiomycosis
Coccidiodes immitis
primary fungal pathogens that cause deep tissue infections
Mostly seen in the Midwest US (Mississippi River Valley)
Found in soil contaminated by bird or bat excreta, entry via inhaled spores
Primary lung infection may be symptomatic in 5%
Lung lesion heals with calcification and fibrosis
Chronic pneumonia and lung cavity
Hematogenous dissemination in immunocompromised host (gingival ulceration)
Predisposition for dissemination: AIDS, chronic corticosteroid therapy
Dx: phagocytosed yeasts seen on Giemsa stain, culture (can be acquired by lab handling) (macro and microconidia at 25 degrees), biopsy, urinary antigen for disseminated disease, complement fixation antibody (cross reaction especially with B. dermatitidis)
Phagocytosed ovoid yeasts found within monocytes and histiocytes; granulomatous reaction
Rx: antifungals
Histoplasmosis
Histoplasma capsulatum
primary fungal pathogens that cause deep tissue infections
Endemic in Central and South America
Inhaled spores enter the lung
Can disseminate to mucus membranes (GIT and skin) – mucocutaneous infection, intestinal ulceration
Yeast resembling a mariner’s wheel
Rx: antifungals
Paracoccidiomycosis
Paracoccidiodes brasiliensis
Usually affect immunocompromised host with either neutrophil or T cell defect
opportunistic fungal pathogens that cause deep tissue infection
opportunistic fungal pathogens that cause deep tissue infection
Commensal on skin and within GIT, most infections are endogenous
Predisposition for invasion: neutropenia (ANC)
Candidiasis
Candida spp.
opportunistic fungal pathogens that cause deep tissue infection
Ubiquitous mold in the environment, spores are inhaled into lungs
Allergic bronchopulmonary aspergillosis
Asthma, central bronchiectasis, immediate skin hypersensitivity to aspergillus antigens, aspergillus precipitins
Aspergilloma
Fungus ball in old lung cavity, may cause severe hemoptysis
Invasive aspergillosis
Affects lungs/sinuses and causes systemic infection
May cause infarctions (eyes, CNS, skin, bone)
Dx: culture and biopsy
Narrow septate hyphae with acute angle branching; predilection for blood vessels causes thromboses and infarction
Rx: antifungals; response to therapy for invasive infections depends on neutrophil function return
Aspergillosis
Aspergillus spp.
opportunistic fungal pathogens that cause deep tissue infection
Predispositions: DM with acidosis, trauma and burns, neutropenia, chelating agent use
Rhinocerebral infection: DKA
Pneumonia: neutropenia
Skin infections: burn and trauma
Dx: culture and biopsy
Broad non-septate or coencocytic hyphae with right angle branching; predilection for blood vessels causes infarction
Rx: surgical debridement and antifungals; sinus infection response to therapy depends on correction of acidosis, lung infection depends on return of neutrophils
Zygomycosis
Zygomycetes: Mucor, Rhizopus, Absidia
opportunistic fungal pathogens that cause deep tissue infection
Ubiquitous yeast worldwide; serotypes A and D (neoformans) in pigeon excreta, serotype B (gatti) in debris under red gum tree
Predispositions: AIDS, prolonged steroids, lymphoma, none in 50% (before AIDS)
Pneumonia, lung cavity, meningitis, dissemination to skin, eye, bone, and prostate
Dx: India ink defines capsule on wet mount; culture (bird seed agar, Sabourad’s agar)sputum, blood, CSF, urine; biopsy and stain with mucicarmine stains (capsule); polysaccharide antigen in blood and CSF (cross reaction with T. beigelii)
Rx: antifungals; chronic suppressive therapy needed for AIDS patients
Cryptococcus
Cryptococcus neoformans
opportunistic fungal pathogen that causes deep tissue infection
dark ovoid sporozoites within cysts on silver stain
often affects AIDS patients and infants
cyst is inhaled by most people in childhood causing a mild pneumonia and latent infection in the lungs
immunocompromised host: reactivation, uncontrolled growth, inflammatory response cause pneumonia
pneumonitis, pneumothorax
Pneumocystis jirovecii
