The Major Mycoses and Causative Fungi Type of Mycosis Causative Fungal Agents Mycosis Endemic (primary, systemic) Paracoccidioides brasiliensis Paracoccidioidomycos is Coccidioides immitis, C posadasii Coccidioidomycosis Histoplasma capsulatum Histoplasmosis Blastomyces dermatitidis Blastomycosis Opportunistic Candida albicans and other Candida species Systemic candidiasis Cryptococcus neoformans Cryptococcosis Aspergillus fumigatus and other Aspergillus species Aspergillosis Species of Rhizopus, Absidia, Mucor, and other Mucormycosis (zygomycosis)
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Ecology Bat and avian habitats (guano); alkaline soil
Geographic distribution
Worldwide, but endemic to Ohio, Mississippi river valleys. (Think OHIstOplama) ; central Africa (var duboisii)
Conidia (< 35 °C)Two kinds of asexual spores:
non encapsulated, Hyaline septate hyphae Mold: Tuberculate macroconidia, macroconidia, 8–16 m, and small oval or pyriform (pear shaped) microconidia, 3–5 m
Tissue formsexual stage :Emmonsiella capsulata
Oval yeasts, 2 x 4 m, intracellular in macrophages **** EXOANTIGEN TESTH. capsulatum : H and M bands
• Giemsa and gram staining do not “take” on the cellwalls of H. capsulatum
• cells often appear to be surrounded by an empty areola
• which was incorrectly taken to be a capsule• + H.capsulatum
Histoplasma capsulatum (Ohio and Mississippi river valleys)
*NOTE: Sepedonium- a fungi characterized by tuberculate macroconidia
Difference: no microconidia and it is a monomorphic fungi
**NOTE: Leishmania speciesDifference: Leishmania do not stain w/ fungal
stain and it has a central nuclear body
Pathogenesis
• Inhaled microconidia develop into yeasts within macrophages.
• (Histoplasma Hides in macrophages) Spreads quickly, calcified granulomas.
Diagnosis• Suitable material for diagnostic analysis:
Bronchial secretionUrinescrapings from infection foci
• For microscopic examination:
Giemsa or Wright staining is applied and yeast cells are looked for inside the macrophages and polymorphonuclear leukocytes.
Cultures on blood Sabouraud agar must be incubated for several weeks. Antibodies are detected using the complement fixation test and agar gel precipitation.
The diagnostic value of positive or negative findings in a histoplasmin scratch test is doubtful.
Diagnosis
• ID budding yeasts WITHIN macrophages.
• DTH skin test w/ histoplasmin
Treatment• Amphotericin B• Itraconazole
BlastomycosisEtiology Blastomyces dermatidis
Ecology Unknown (riverbanks?)
Geographic distribution Endemic along Mississippi, Ohio, and St. Lawrence River Valleys and in Southeastern United States
Conidia (< 35 °C) YEAST FORM : Round yeast w/ doubly refractive wall, single broad based bud
MOLD FORM : Branched hyphae w/ small conidia bearing single globose to piriform conidia, 2–10 m
Tissue form Thick-walled yeasts with broad-based, usually single buds, 8–15 m
North American Blastomycosis/ Gilchrist’s disease
• RT: Mold: lollipop conidia• 37C: Yeast: yeast cell w/ broad based single budding· ****EXOANTIGEN TEST
Test for:• systemic fungi (immunodiffusion)• B. dermatitidis : appearance of spc. A band
Treatment
• Amphotericin B• Itraconazole
Blastomyces dermatitidis
A: In tissue or culture at 37 °C.
B: In culture at 30 °C on Sabouraud's agar
Budding yeast cells of Blastomyces dermatitidis in culture. When cultures are incubated at 37°C, large, broad-based budding yeast with a double-contoured all are detected which are characteristic for the yeast phase of this dimorphic fungus. (Lactophenol cotton blue stain; ×400)
Mould form of Blastomyces dermatitidis in culture. The lollipop appearance of the conidium on a conidiophore is characteristic of the environmental mould form for this dimorphic fungus. (Lactophenol cotton blue stain; ×400)
Paracoccidioidomycosis
Etiology Paracoccidioides brasiliensis
Ecology Soil fungus
Geographic distribution Central and South AmericaLatin America
Conidia (< 35 °C)
YEAST FORM
Tissue form
Hyaline, branched septate hyphae and rare globose conidia and chlamydospores
Round yeast w/ thick wall andmultiple buds
Hyaline, septate hyphae and rare globose conidia and chlamydospores
Treatment Combination therapy of amphotericin B Fluconazole offers excellent penetration of the central nervous system Highly Active Antiretroviral Therapy (HAART) better prognosis for
HIV/AIDS
Aspergillus
YEAST FORM: NONE
MOLD FORM: V-shaped septate hyphae w/ radiating chains of conidia
Aspergillus fumigatus
Invasive necrotizing pneumonia in AIDS, Molds grow in pulmonary cavities and produce
Aspergilloma (FUNGUS BALL), requiring surgery.Allergic bronchopulmonaryaspergillosis, type I hypersensitivity reaction like asthma.
A.flavus- grows on cereal or nuts produces aflatoxins (toxic, carcinogenic to liver)
Microscopic ExaminationKOH or calcofluor white histologic sections
• +hyaline, septate, and uniform in width (about 4 m) and branch dichotomously
Culture room temperature - + CONIDIA
Diagnostic Laboratory TestsSerology• precipitins positive aspergilloma or allergic forms of aspergillosis• circulating cell wall galactomannan is diagnostic.
TreatmentAspergilloma -itraconazole - amphotericin B and surgeryLess severe chronic necrotizing pulmonary disease -voriconazole - itraconazoleAllergic forms of aspergillosis -corticosteroids -disodium chromoglycate
Mucor/Rhizopus
YEAST FORM: NONE
MOLD FORM: Right-angle branched nonseptate
hyphae w/ sporangiumGray to brown to black colony filling a Petri dish in 2 to 3 days.
Characteristics
• Nonseptate hyphae w/ broad irregular walls and right angle branches (compare w/ aspergillus)
• Endospores inside of sporangium
Diseases
• Rhinocerebral mucormycosis- associated w/ diabetes, caused by infection of nasal mucosa with invasion of sinuses/orbit. Molds proliferate in walls of blood vessels.
• (Think MUCOR/Rhizopus invades MUCOSA)• Important in immunocompromized patients paricularly leukemic patients
Habitat/Trans
• Saprophytic molds• EVERYWHERE!
Diagnosis:Biopsy
Treatment:Amphotericin B,Surgical resection
Penicillium marneffei
• A dimorphic fungus grow as mold at 25 °C and as arthroconidia at 37 °C
• causes tuberculosis-like disease in AIDS patients