Fungi Flashcards
(11 cards)
Tinea versicolor
Malassezia furfur causes Pityriasis versicolor
Normal skin flora, thrives in hot and humid conditions
Characteristics: “spaghetti and meatball” appearance on KOH prep
Hypo or hyperpigmented patches of skin in healthy individuals- usually back and chest; increased incidence in those who spend time in sun
Mechanism: lipid degradation-> acid damages melanocytes; fungus stays in stratum corneum
Neonates receiving TPN (lipid infusion) -> can get disseminated malassezia furfur -> sepsis and thrombocytopenia
Treatment: topical selsun blue (selenium sulfide)
Tinea (Dermatophytes)
Dermatophytes cause tinea (ringworm) erythematous scaling rings
Normal skin flora
Types:
- Trichophyton
- Epidermophyton
- Microsporum
Tinea capitis - head and scalp
Tinea corporis - body (have central clearing)
Tinea cruris - groin “jock itch” (no central clearing)
Tinea pedis - “athlete’s foot”
Tinea unguium - onychomycosis
At risk: athletes, pets can transmit
Pruritic lesions
Diagnosis:
Hyphae on KOH prep
Treatment:
topical azoles
oral -Terbinafine for onychomycosis
Grisleofulvin (severe infections)
Sporothrix schenckii
Characteristics: dimorphic fungus, branching hyphae at 25C, “cigar shaped” budding yeast
Mechanism: enters via cut by thorns (found on plants, roses etc)-> local pustule at site -> nodules ascend via draining lymphatics
Symptoms: cutaneous nodules and ulcers in lymphatic pattern
Diagnosis:
Culture
biopsy: granulomas w/ cigar-shaped yeast
Treatment: Itraconazole, potassium iodide
Candida albicans
Characteristics:
- Dimorphic- psuedohyphae at 20C (yeast in cold) and germ tubes at 37C (mold in heat)
- Catalase (+) (CGD susceptible)
Normal flora of GI tract
Mechanism: Opportunistic mycosis. Cutaneous or systemic.
Symptoms:
- Diaper rash (heat and humidity)
- Oral candidiasis (immunocompromised or use of steroids) -> can be scraped off
- Candidal esophagitis (AIDS defining illness, start seeing at CD4 kill vaginal flora and allow candida to grow; NORMAL pH 4
- Endocarditis - in IV drug users -> tricuspid valve
Treatment:
- Azoles for minor infections
- amphotericin B for severe infections
- Oral/esophageal candidiasis: nystatin (swish and spit/swallow)
- Capsofungin for disseminated disease
Aspergillus fumigatus
Characteristics:
- Catalase (+) (CGD risk)
- Hyphae have septate and acute angle ( carcinogenic -> HCC*
Transmission: conidiophores with fruiting bodies -> released in air and inhaled by humans
Presentation:
- Allergic bronchopulmonary asperigillosis (ABPA)
- type 1 hypersensitivity: wheezing, fever and migratory pulmonary infiltrate; associated with asthma and CF; Increased IgE - Asperigillomas
- fungus balls in lungs
- increased susceptibility in those with lung lesions already (TB cavity ex)
- gravity dependent -> fungus at bottom of cavity - Angioinvasive aspirgillosis
- immunocompromised: neutropenia from leukemia/lymphoma
- disseminates into blood and surrounding tissues
- fever, cough, hemoptysis
- kidney failure
- endocarditis
- ring enhancing brain lesions
- necrosis around nose
Treatment:
Voriconazole for less serious infection
Aspergillomas must be surgically debrided
Disseminated disease- amphoterecin B
Cryptococcus neoformans
Characteristics:
- Heavily encapsulated yeast (NOT dimorphic)
- Capsule: repeating polyscaccharide antigen -> antiphagocytic virulence factor
- Transmitted: soil and pigeon droppings -> inhaled -> lungs is primary focus
- Urease (+)
- Bronchopulmonary lavage to diagnose -> mucicarmine or methanamine silver stain
- LP: india ink stain, wide capsular halos
- Latex agglutination test: agglutination of capsular antigen
Presentation:
Usually in immunocompromised
1. Lungs- often asymptomatic, can have cryptococcus pneumonia
2. May spread to CSF-> Most common cause of fungal meningitis -> neuro deficits
3. Fever
Gross pathology:
*Soap bubble lesions in grey matter with cryptococcus meningitis
Treatment of Cryptococcus meningitis:
amphotericin B + flucytocin followed by maintenance with fluconazole
Mucormycosis
Caused by Mucor and rhizopus
Characteristics:
- Bread mold
- Transmitted: spore inhalation -> proliferate in vessel walls where excess glucose and ketones (high risk in DKA)
- Morphology: hyphae nonseptate, wide angle-branching (90deg)
Presentation:
-immunocompromised at risk
esp leukemia and neutropenia
-diabetics at risk (DKA!!)
-Goes through cribiform plate and enters brain -> necrosis –> rhinocerebral mucormycosis and frontal cortex abscesses
-Black eschar on face and nasal cavity –> very bad prognosis
Treatment:
Dead tissue debridement
Amphotericin B
Pneumocystic jiroveci
Pneumocystis pneumonia (PCP)
Characteristics:
- Associated with AIDS (asymptomatic in immunocompetent)
- transmitted via inhalation
- AIDS defining illness, CD4 disk (ovoid) shaped yeast
Presentation:
- diffuse interstitial pneumonia
- ground glass appearance on CXR
- non-productive cough
Treatment and Prophylaxis: must start with HIV CD4
Histoplasmosis
Location: MS and OH River valleys; bird or bat droppings (caves)
Characteristics:
- Dimorphic, mold in cold, yeast in heat
- Macrophage filled with ovoid cells (histoplasma); Histoplasma size
Blastomycosis
Location: E of MS river and Central America (Great lakes and OH River valley)
Transmission: inhalation of spores
Characteristics:
- Dimorphic, mold in cold, yeast in heat
- Broad-based buds, same size as RBC
Presentation:
Inflammatory lung disease
Can disseminate to bones and skin -> granulomatous nodules
Treatment:
local- fluconazole or itraconazole
systemic- amphotericin B
Treatment:
local- fluconazole or itraconazole
systemic- amphotericin B
Coccidiodomycosis
Location: SW U.S.; “San Joaquin Valley fever”
Transmission: spores in air after earthquakes -> inhalation
Characteristics:
- Dimorphic, mold in cold, yeast in heat
- Spherule much larger than RBC filled with round endospores
Presentation:
- pneumonia
- meningitis
- ‘desert bumps’ - erythema nodosum
- ‘desert rheumatism’ - arthralgias
Treatment:
local- fluconazole or itraconazole
systemic- amphotericin B
