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Microbiology and Immunology 2500A/B Lecture Notes - Blastomycosis, Histoplasmosis, Sporotrichosis

Microbiology and Immunology
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Lecture 10: Mycology II 10/01/2012
Laboratories without biological safety cabinets must not work on any mold, except those believed to be
There are several identification criteria:
1. Growth rate in culture
2. Presence of a yeast phase (is it dimorphic?)
3. Colonial and microscopic morphology (most important)
4. Biochemical tests
Mold Classification
Examination of the hyphae enables classification into 3 groups:
1. Septate unpigmented hyphae (hyaline). Includes the majority of medically important molds.
2. Septate brown pigmented hyphae (dematiaceous)
3. Aseptate wide hyphae, characteristic of the lower fungi Mucorales
Hyaline Hyphae
Hyaline means looks like glass
No pigment
Hyaline Molds: Aspergillus
Smoky, gray/green fuzzy colonies
Invasive infections in severely immunocompromised patients, especially with prolonged neutropenia. Mortality
is greater than 50%
Cause chronic sinusitis and aspergilloma (fungus ball in preexisting pulmonary cavity) in immunocompetent
Aspergillus species:
1. Aspergillus fumigatus also causes allergic bronchopulmonary aspergillosis in asthmatics and CF patients
2. Aspergillus niger commonly causes otomycosis
3. Aspergillus flavus may infect immunocompromised patients and also infects peanuts, producing
aflatoxin which is associated with liver carcinoma
4. Aspergillus terreus
Aspergillus Hyphae in Tissue
Tissue biopsy need silver stain to differentiate fungal elements
Repeated branching, but eventually end up going in the same direction (same behaviour as schooling fish)
Hyaline Molds: Penicillium
Rapidly growing greenish colony which you often see on moldy bread
Source of penicillin
One invasive species: Penicillium marneffei
Penicillin inhibits bacterial growth
Trichophyton spp. (red colony makes it easy to identify)
Microsporium spp.
Epidermophyton floccosum
Tinea Pedis (Athelete’s Foot)
Dark, moist conditions to get Athlete’s foot
Fungal infection of the foot
Tinea Corporis (Ringworm)
When it happens on the body, it is called ringworm
Fungal infection of the body
Disfiguring infections due to demataceous fungi
Fonsecaea pedrosoi most common
Phialophora verrucosa, Fonsecaea compacta,
Cladosporium carrionii, Rhinocladiella
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