Microbiology - Mycology

zepowulu's version from 2016-03-17 12:16

Microbiology: Mycology

Systemic Mycoses

Question Answer
all causepneumonia (can disseminate)
cold meansmold
heat meansyeast
Rx for local inffluconazole or ketoconazole
Rx for systemic infamphotericin
systemic mycoses mimicTB (granuloma formation)


DiseaseEndemic location and pathological features
histoplasmosisMississippi, Ohio river valleys
causes mild/chronic(AIDS) pneumonia
hides in macrophages (smaller than RBC)
From bird or bat droppings
"Histo hides"
blastomycosiseast of Mississippi R and central America
causes inflammatory lung disease
Fever chills wt loss, disseminates to skin and bone, forms granulomatous nodules
single broad-base budding - same size as RBC.
Found in rotten wood/beaver damns, soil
"Blasto buds broadly"
coccidioidomycosisSW USA, California, Mild Lung infection/pneumonia and meningitis, can disseminate to bone and skin
Desert bump --Erythema Nodosum(red tender nodules)
Desert valley fever
Pregnant 3rd trimester
Case rate incrs after earthquakes (spherules in dust thrown up in air)
"Coccidio crowds"
paracoccidioidomycosisAsymptomatic lung lesions and mild pneumonia
thick walled yeast w/ multiple buds
In Latin America
"captain's wheel" formation - Larger than RBC

Cutaneous Mycoses

Question Answer
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
tinea versicolor Rxtopical miconazole, selenium sulfide (Selsun)
tinea pedis (foot)/tinea cruris (groin)/tinea corporis (ringworm on body)/tinea capitis (head, scalp)pruritic lesions with central clearing like a ring, caused by dermatophytes (Microsporum, Trichophyton, Epidermophyton), mold hyphae in KOH prep not dimorphic, pets reservoir for Microsporum
Microsporum Rxtopical azoles

Opportunistic Fungal Infections

Question Answer
Candida albicanssystemic or superficial
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 candidiasis
Candid albicans Rxnystatin (topical azole) for supf inf, amphotericin B, fluconazole, or caspofungin for systemic inf
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
some species of Aspergillus produce aflatoxins → hepatocellular carcinoma
mold with septate hyphae that branch at acute angles, not dimorphic
"Acute Angles in Aspergillus"

Conidiophor with radiating chains of spores:
Cryptococcus neoformanscryptococcal meningitis
culture on Sabouraud's agar
heavily encapsulated yeast
not dimorphic
found in soil and pigeon droppings - acqr'd through inhalation → hematogenous dissemination to mininges
stains with India ink, latex agglut test detects polysacc capsular antigen
"soap bubble" lesions in brain
Mucor and Rhizopus sppmucormycosis - mostly in ketoacidotic diabetic and leukemic patients
fungi prolif in blood vessel walls when there is excess ketone and glucose
mold with irreg nonseptate hyphae branching at wide angles
penetrate cribiform plate and enter brain → rhinocerebral, frontal lobe abscesses
headache, facial pain, black necrotic eschar (a dry, dark scab or falling away of dead skin) on face
cranial nerve involvement
Pneumocystitis jiroveci (PCP)causes diffuse interstitial pneumonia
disc-shaped yeast
usually asymp. immunosup predisposes to disease.
diffuse, bilateral CXR appearance. "" GROUND GLASS OPACITIES ''
dx by lung biopsy or lavage. ID by methenamine silver stain of lung tissue
Pneumocystitis jiroveci RxTMP-SMX, pentamidine, dapsone; start prophylaxis when CD4 drops <200 cells/mL in HIV
Sporothrix schenckiisporotrichosis.
dimorphic fungus - cigar-shaped, budding yeast
lives on vegetation.
traumatically introduced into skin ("rose gardener's" disease)
causes local pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis).
little systemic illness.
Sporothrix schenckii Rxitraconazole or potassium iodide


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
Microsporummold hyphae on KOH prep, not dimorphic
Trichophytonmold hyphae on KOH prep, not dimorphic
Epidermophytonmold hyphae on KOH prep, not dimorphic
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 "" Disc shaped ''
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