05-01 Geographic Fungi (Ch 18) Flashcards
To be able to name the diseases caused by the four most important systemic fungal pathogens, and one emerging disease, where they are found, their clinical symptoms, when they should be considered in diagnosis, and how they are treated.
What are the four most important systemic fungi and the one emerging pathogen we learned about?
—What disease does each cause?
- Histoplasma capsulatum HISTOPLASMOSIS
- Blastomyces dermatitidis BLASTOMYCOSIS
- Cocci immitis/posadasii COCCIDOIDMYC.
- Sporothrix schenckii SPOROTRICHOSIS
Emerging (Optional)
5. Penicilliosis marneffei PENICILLINOSIS
Which forms do dimorphic fungi form where?
IN NATURE
—septate hyphae (crosswalled, indiv filaments) that form mycelium
IN HOST
—yeast (round or oval), divide by budding
Histoplasma capsulatum —where found? —clinical symptoms? —when they should be considered in diagnosis? —dx? —tx?
HISTOPLASMOSIS
intracellular; similar granuloma to TB
—where found: in moist soil with bird or bat droppings; in MS/OH + St. Lawr River Valleys; Ctrl/S Amer
—clinical symptoms?
a. PRIMARY: Freq asx or mild; may be flu-like w/ cough, F, malaise, hilar adenopathy
—Can lead to mediastinal fibrosis, w/ fibrous encasement of major vessels.
b. RE-INFX: exposure to large #s of aerosolized spores in prev infected indiv may result in febrile illness w/ acute pulm infiltrates
c. CHRONIC (cavitary) pulm: Progressive fibrous and nodular apical infiltrates, which cavitate. Clinical find- ings of cough, fever, and weight loss, mostly in men over 40.
d. DISSEMINATED: some acute infections go on to disseminate to multiple organs, resembling miliary TB. This is a chronic progressive infection in AIDS.
—when they should be considered in diagnosis?
working in soil, chicken coops, caves, old houses, HIV+
—dx:
Culture: fruiting bodies (wheel with knobs)
Histopathology: M0s stuffed w/ small budding yeasts are seen in LNs, spleen, liver, and bone marrow. Granulomas in lungs, others, around BVs
Serology: blood Ab or URINE antigen
—tx: itraconazole; AmpB if severe
Blastomyces dermatitidis —where found? —clinical symptoms? —when they should be considered in diagnosis? —dx? —tx?
BLASTOMYCOSIS (Extracellular)
—Found: overlaps Histo, but less common
—moist soils, river/pond edge
— ♂ > ♀
CLINICAL SX
—PULM infx prob most freq, sometimes asx
—CUTANEOUS – uncommon- lesion can be verrucous, or can ulcerate and resemble squamous carcinoma grossly and microscopically.
—BONE - one of the few fungal infections with a predilection for this site
—DISSEMINATED – GU tract, CNS
DIAGNOSIS
a. Stains of pus / tissue, histopathology show the yeast forms
b. Culture – mycelial form appears in days to wks. “Lollypop” fruiting structures on hyphae
c. Serology not useful, Abx are broadly cross-reactive w/ other fungal Ags
TX
a. Amphotericin B for serious or progressive dz
b. Itraconazole for non-meningeal dz of mod severity
Coccidoides immitis/posadasii —where found? —clinical symptoms? —when they should be considered in diagnosis? —dx? —tx?
COCCIDIOIDOMYCOSIS
a. Inhalation of arthrospores, pulmonary infection, possible hematogenous dissemination.
b. Granulomatous response, endospores in characteristic spherules of varying size, no true yeast forms seen. In patients with bronchiectasis, mycelial forms can be seen where the organism is exposed to the air.
EPIDEMIOLOGY
—Found in Sonoran, San Joaq/Central Valleys Ctr/SAmer
CLINICAL FINDINGS
a. Primary pulmonary - Valley fever: fever, cough, fatigue, arthralgias
b. Sometimes associated with eosinophilia (25% of pts), Erythema nodosum (also assoc with other infections)
c. Disseminated - bone, skin, meninges, higher risk in pregnancy, black and Filipino populations. This is an important disease in AIDS patients.
DIAGNOSIS
a. Serology, complement fixation, immunoprecipitin and ELISA tests
b. Culture – sputum or tissue can be sampled, the white fluffy mycelia appear within one week. This is a very hazardous culture in the laboratory; the barrel-shaped arthrospores are easily aerosolized
c. Histopathology; identify endospores within granulomatous reaction.
TREATMENT
a. Most primary disease is not treated
b. Amphotericin B for progressive primary disease and immunosupressed patients
c. Meningitis: intrathecal Ampho B
d. ? Role of Azoles, may be used for chronic treatment in the immunosupressed.
Sporothrix schenckii —where found? —clinical symptoms? —when they should be considered in diagnosis? —tx?
SPOROTRICHOSIS
FOUND Worldwide; rotting wood, roses, sphag moss
PATHOGENESIS/PATHOLOGY
a. local inoculation, frequently upper limb
b. pyogranulomatous response
c. lymphangitic spread
CLINICAL SYNDROMES
a. CUTANEOUS lymphangitis with nodules (not in classic lymph nodes), more serious infections have osteoarticular involvement and tenosynovitis. Systemic symptoms rare.
b. PULMONARY, uncommon, can cavitate, more frequent in men, 30-60 yrs. c.Disseminated in immunosuppressed
DIAGNOSIS
a. Culture, yeast-like colonies grow in one week, begin to convert to mycelia at room temperature.
b. Histopath difficult, “cigar-shaped” yeast not easy to find
c. Serology not useful
TREATMENT
a. K+ iodide, may increase M0 intracell killing mechs
b. Local heat for cutaneous lesions
c. Itraconazole may have fewer side effects than iodide.
Penicilliosis marneffei —where found? —clinical symptoms? —when they should be considered in diagnosis? —tx?
GEOGRAPHIC DISTRIB
SE Asia, imported cases uncommon here. Remember travel Hx
CLINICAL SYNDROME
Respiratory and disseminated systemic infections in the immunosupressed
DIAGNOSIS
Growth of mold with diffusible red pigment, Penicillium fruiting structures in culture, yeast-like forms with binary fission in tissue.
TREATMENT
Amphotericin B, possibly itraconazole or voriconazole.
