Mycology Flashcards
What fungi can cause systemic mycoses?
Histoplasmosis
Blastomycosis
Coccidioidomycosis
Paracoccidioidomycosis
Notes about the systemic mycoses inducing fungi
- All can cause pneumonia and can disseminate
- All are dimorphic fungi (cold (20C)= mold; heat (37C)= yeast)- the only exception is coccoidomycosis, which is a spherule (not yeast) in tissue
Tx with fluconazole or itra for local infection and ampho B for systemic
Systemic mycoses can mimic TB (granuloma formation) but…
they have no person-person transmission
What is this?
Histoplasmosis (histo bodies within macrophages)- associated with brid or bat droppings
Where is Histoplasmosis endemic?
Mississippi and Ohio River Valleys- causes pneumonia
Blastomycosis-broad-based buding (same size as RBCs)
Blastomycosis- causes inflammatory lung disease and can disseminate to skin and bone (forms granulomatous nodules)
Blastomycosis- common in states east of the Mississippi River and Central America
Coccidioidomycosis- spherules (much larger than RBCs)- filled with endospores
Coccidioidomycosis
Where is Coccidioidomycosis common?
Southwestern US, California- causes meningitis and penumonia and can disseminate to bone and skin
Common after earthquakes when spores are thrown into the air and inhaled to form spherules
Paracoccidioidoycosis- budding yeast with ‘captains wheel’ formation
Paracoccidioidoycosis-common in Latin America
What are the major cutaneous mycoses?
TInea (dermatophytes)- capitis, corporis, cruris, pedis, unguium
Tinea versicolor
Dermatophytes (tinea) include what spp?
Microsporum
Trichophyton
Epidermophyton
How is Tinea diagnosed?
branching septate hyphae visible on KOH prep with blue fungal stain
How does tinea capitis present?
Occurs on head, scalp, and is associated with LD< alopcia, and scaling
How does tinea corporis present?
Occurs on the body and is marked by erythematous scaling rings (ringworm) and central clearing- can be acquired from contact with an infected dog or cat
How does tinea cruris present?
Occurs in inguinal area and often DOES NOT show the central clearing seen in tinea corporis
Describe tinea pedia
3 varieties:
Interdigital (most common) (below)
Moccasin distribution
Vesicular types
Tinea pedis- Vesicular type
Tinea pedis- Moccasin type
Describe Tinea unguium
Onchomycosis; occurs on nails
What causes Tinea versicolor?
Malassezia spp (Pityrosporum spp.), a yeast-like fungus (not a dermatophyte despite being called tinea)
NOTE: Below: degradation of lipids produces acids that daage melanocytes and cause hypopigmentation and/or pink patches
When is Tinea versicolor most common?
summer (hot, humid weather)
What does Tinea versicolor look like on microscopy?
Spaghetti and meatballs
What are the main opportunistic fungal infections?
Candida albicans
Aspergillus fumigatus
Crytpococcus neoformans
Mucor and Rhizopus spp.
What is this?
Candida albicans- pseudohyphae and budding yeasts at 20C and germ tubes at 37C
Candida can cause oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDs), vulvoganitis (diabets, ABX users), diaper rash, endocarditis in IVDU, disseminated candidiasis
Candida vulvovaginitis
How is Candida tx?
topical axzole for vaginal
nystatin, fluconazole, or caspofungin for oral/esophagel
fluconazole, caspofungin, or ampho B for systemic
Aspergillus fumigatus- invasive aspergillosis, especially in immunocompromised and those with chronic granulomatous disease
Diagnosis: Septate hyphae that branch at 45 degrees (ACUTE!!)
NOT dimorphic
What diseases does Aspergillus fumigatus cause?
Alergic bronchopulmonary aspergillosis (ABPA)- associated with asthma and cystic fibrosis; may cause bronchiectasis and eosinophilia
Aspergillomas in lung cavities, especially after TB infection
Some species of Aspergillus produce _______
alfatoxins, which are associated with hepatocellular carcinoma
What is this?
Cryptococcus neoformans, the cause of cryptococcosis
What is the structure of Cryptococcus neoformans?
heavily encapsulated yeast (not dimorphic)
What is the major association of Cryptococcus neoformans?
soil and pigeon droppings (acquired through inhalation with heme dissemination to meninges)
How is Cryptococcus neoformans confirmed?
India Ink or mucicarmine stain
culture on Saboruaud agar
Latex agglutination test detects polysaccharide capsular antigen and is more specific
Crypto- soap bubble lesion in brains
Crypto- soap bubble lesion in brains
What fungal disease is most common in ketoacidotic diabetics and/or neutropenic pts (e.g. leukemia)?
Mucormycosis
Mucomycosis- look for rhinocerebeal, frontal lobe abscesses, or cavernous sinus thrombosis
HA, facial pain, and black necrotic eschars on face common
Wide angle branching hyphae!!
How is Mucormycosis tx?
surgical debridement and ampho B
What is the cause of Pneumocystis pneumonia (PCP)?
Pneumocystis jirovecii
Describe Pneumocystis jirovecii
This is a yeast like fungus that is inhaled and most infections are asymptomatic and immunosuppression predisposes to disease.
How does PCP present?
diffuse, bilateral ground-glass opacitices on CXR/CT
Opacities seen with PCP- look near the back of each lung
How is PCP diagnosed?
lung lavage or lung biopsy
How does Pneumocystis jirovecii appear on methanmine silver stain of lung tissue?
Disc-dhaped yeast form
How is PCP tx?
TMP-SMX, pentamidine, dapsone (prophylaxis only), atovaquone (prophylaxis only)- make sure to start prophylaxis when CD4+ count drops below 200/MM3 in HIV pts.
What is this?
Sporotrichosis (sporothrix schenckii)
Describe Sporothrix schenckii
dimorphic, cigar-shaped budding yeast that lives on vegetation
How is Sporothrix schenckii transmitted?
When spores are traumatically introduced into the skin, typically by a thorn (rose gardener’ disease), it causes a local pustule or ulcer with nodules along draining lymphatics (asending lymphangitis)
Disseminated disease possible in immunocompromised hosts
How is Sporothrix schenckii tx?
itra or posassium iodidi
