Mycology

Question 1

Candida albicans

Answer 1

Normal flora - skin, GI, female genital tract

Scrape off leaves raw bleeding mucosa

Dx: blood culture: germ tubes - small projections on side of cell

Tx:
Superficial: Nystatin, clotrimazole, fluconazole

Systemic: fluconazole (normal immune), amphotericin B, Echinocandin

Question 2

Oral thrush

Answer 2

white, curd like patches - top of tongue

immunocompromised - common in AIDS
DM
Chronic steroids
Neonates
inhales steroids

Question 3

Candida vulvovaginitis

Answer 3

MC in DM, recent abx use

Sx: severe itching
edema
vaginal discharge

assoc w/ acidic pH

Question 4

Candida diaper rash

Answer 4

erythematous skin, shines or eroded
edge of red area - jagged edge

satellite lesions - smaller, outside central lesion

Question 5

Intertrigo

Answer 5

Candida infection under breast or skin folds of obese pts

erythematous central lesions w/ satellite lesions

Question 6

Candida blood infections

Answer 6

central lines, drug users

Leads to:
endophthalmitis
Endocarditis

Question 7

Chronic mucocutaneous candidiasis

Answer 7

inherent immune deficiency

Question 8

molds considered dermatophytes

Answer 8

Trichophyton
Micosporum - dog/cat –> human
epidermophyton
malassezia furfur

Question 9

Cryptococcus neoformans

Answer 9

AIDS: cryptococcal meningitis

heavily encapsulated yeast
reproduce by narrow-based budding

found in soil and pigeon droppings

cultured on most bacterial and fungal media
Sabouraud’s agar

India ink - stains everything but capsule - CSF and other specimens

Serologic test: cryptococcal ag

Latex agglutination test to detect polysaccharide capsular Ab

“Soap bubble” lesion in brain on imaging

Tx: amphotericin B + flucytosine, followed by fluconazole

Question 10

Pneumocystis jirovecii

Answer 10

Yeast
PCP - diffuse interstitial pneumonia
potentially fatal in immunocompromised

Dx:
silver stain
imaging: ground glass appearing interstitial infiltrates

Tx: TMP-SMX
Sulfa allergy: pentamidine, clindamycin + primaquine
Severe + prednisone

Prophylaxis: CD4 under 200 - TMP-SMX

Question 11

Aspergillus fumigatus

Answer 11

allergic bronchopulmonary aspergillosis
Fungus ball - aspergilloma
Invasive aspergillosis -immunocompromised

Ubiquitous fungus

Dx: narrow septet hyphae
branched at acute angles about 45 degrees
MOLD!

Tx: voriconazole, lipid formulation of amphotericin B

Question 12

Mucor and Rhizopus

Answer 12

cause mucormycosis
-ubiquitous

Invasive dz:
severly immunocompromised
DM
trauma pt

Molds: broad, irregularly shaped nonseptate hyphae, branching right angles

flip M upside down to W = wide angle

Question 13

Rhinocerebral mucormycosis

Answer 13

DM esp DKA and leukemia w/ neutropenia

head pain and HA

• -> large necrotic lesions like black eschar of palate/nose
• -> CN deficits, blindness

high mortality

Dx: bx

Tx: surgical debridement
Amphotericin B

Question 14

Infections caused by dermatophytes

Answer 14

Tinea pedis - feet
Tinea cruris - groin
Tinea corporis - body
Tinea capitis - head
Dx: fungal hyphae or spores on skin or hair samples
Cx

Tx: simple skin infections - topical terbinafine or azole
Extensive skin infections or scalp/hair: oral terbinafine or azole

Tinea unguium (nails) - nail plate, thickened, discolored nails
Tx: orally: terbinafine, itraconazole, fluconazole
-6wk - 6 mo for fingernails
-12 wks - 12 mo toe nails

Question 15

Tinea versicolor

Answer 15

malassezia furor
lipophilic yeast –> hypo pigmented patches on body (or hyper)
-trunk and proximal limbs

small areas coalesce w/ scaling plaque

**KOH prep: spaghetti and meatballs appearance **

Question 16

Treatment of mycoses

Answer 16

Localized uncomplicated infections: fluconazole, itraconazole

Severe, disseminated, complicated infections: amphotericin B

Question 17

Systemic mycoses

Answer 17

Cause caseating and non-caseating granulomas

Cx on Sabouraud agar

Question 18

Histoplasma capsulatum

Answer 18

Mississippi and Ohio river valleys
Bird and bat guano

Enters through lung, engulfed by N0 or M0
“Histo hides in M0”

Histo: M0 w/ hundreds of yeast forms in cystoplasm

Yeast – smaller than RBCs

Self limited pneumonia, minimal sx

Can become severe pneumonia or disseminated dz

Question 19

Blastomyces dermatitidis

Answer 19

States bordering Mississippi and Ohio river basins up to Canada, Central America

Enters via pulmonary route -> pulmonary infection

Can lead to disseminated dz: skin, bone, granulomatous nodules

Thick refractile wall around yeast forms

Same size as RBCs

Reproduce by Broad Based Budding!

Question 20

Coccidiodes immitis

Answer 20

Mycelial form in soil -> spherule

Dried out mycelial forms fracture into arthroconidia
-go airborne, stay in air for long periods of time
deposit in lungs

barrel shaped in air
In lung spherule fills w/ endospores

Larger than RBC
Release endospores into surrounding tissues

Southwestern US, Mexico, C. America
San Joaquin Valley Fever

Asx or mild
Severe pneumonia
Disseminated dz: CNS (meningitis), skin, bone, joints

Question 21

Sporothrix schenckii

Answer 21

Soil and vegetation
Thorns
Sphangnum moss

Small pustule/ucer at site of initial infection
Nodules appear along draining lymphatics
Painless

Tx: itraconazole, potassium iodide (kids)
“plant a rose in a Pot(assium iodide)”

Question 22

Paracoccidiodes brasiliensis

Answer 22

Latin America

Enters through respiratory route

Disseminates widely progressive dz

• severe pneumonia
• granulomatous changes in mucous membranes and skin

captain’s wheel appearance