Multicellular Branching Filamentous (hyphae) Forms

• Mass of hyphae is a mycelium
• Asexual reproduction results in spores formed from hyphae
• Sexual spores as well (less common)

Unicellular Yeast

• Reproduce by budding or division

3 layers of polysaccharides

Glycoproteins

Beta-Glucans

Alpha-Glucans

Chitin and Mannans are significant components of fungal cell wall

Main Sterol Components of Cell Membrane

Ergosterol

Zymosterol

• Inhalation
• Ingestion
• Injection

Low pH

Fatty acids

Turnover of skin

IgA, IgG at mucosal surfaces

Our own flora

1. Hypersensitivity to fungal antigens
2. Production of mycotoxins (exotoxins)
3. Mycoses - growth of a fungus on or in the body

1. Superficial
2. Subcutaneous
3. Systemic (primary pathogenic and opportunistic fungi)

• Body surface (skin, hair, nails)

Ex: dermatophytosis (ringworm) affects outermost keratinized tissues of the hair, nails, and stratum corneum of the skin

• Confined to the dermis, subcutaneous tissue, or adjacent structures

Ex: Rare and confined to tropical regions of the world; usually result from inoculation of saprophytic fungi from soil into subcutaneous tissue (via thorn, insect bite, fish spine)

• Internal organs, systems
• May result from inhalation of air-borne spores, ingestion, or IV lines

Primary Pathogenic Fungi

• Infections occurs in previously healthy persons and arises through a respiratory route
• Ex: Histoplasmosis

Systemic Opportunistic Fungi

• Cause diseases in immune compromised hosts
• Endogenous (Candida albicans)
• Exogenous (?)

• Infection of skin, hair, nails, and outer layers of epidermis
• Causes dermatomycoses
• Secrete keratinase, an enzyme that degrades keratin

Trichophyton

Microsporium

Epidermophyton (Tinea capitis, pedis, cruris, corporis)

• Many pathogenic species are dimorphic
• Capable of changing from multicellular mold form in nature to a budding single celled form when causing an infection
• Switches to dimorphic based on environmental, temperature, and nutritional changes

Ex: Histoplasma capsulatum

• Histoplasma capsulatum
• Route of infection: inhalation
• Upon inhalation, small budding forms phagocytosed; infection of macrophages and histiocytes
• Transient spread leads to flu-like symptoms
• Hepatosplenomegaly in immunocompromised patients
• Bat, bird feces provides nutrients for the fungus

• Coccidioides immitis
• Spores found in dry soils of the Southwestern US, Central America, South America
• Highly infective in dusts in endemic areas
• Like Histoplasmosis, may be asymptomatic; may present as flu-like illness, similar to Tuberculosis
• Hyphal growth in lung

• Aspergillus fumigatus, A. niger, A. flavus
• Dangerous in immunocompromised patients
• Aspergillus spores are nearly everywhere
• Causes severe allergies
• Aspergillosis of the lung (aspergilloma) may be contained but systemic aspergillosis has a high mortality

Aspergillus flavus

• It is an aromatic amine derivative
• From peanuts, grains
• Mutagenic effects on the liver (forms liver tumors)

Cryptococcus neoformans

• Encapsulated yeast that is inhaled
• Leads to meningoencephalitis
• May also involve skin, UT, eyes, lungs, bones, joints, myocardium, prostate gland

1.  Weakly Encapsulated

• in high glucose or high salts, conditions that may be found in nature, C. neoformans becomes weakly encapsulated
• the small size is necessary for the organism to get into the alveolar spaces in the lung

2.  Thick Polysaccharide (Rehydrated) Capsule

• once in the lungs, the organism can become rehydrated and acquire a thick polysaccharide capsule

Pneumocystis carinii (Pneumocystis jiroveci)

• Opportunistic infection of elderly, premature babies, immune compromised
• Lung tissue infected --> filling of alveoli w/ fluids

• Nonfilamentous, unicellular; typically oval or spherical
• Like molds, found almost everywhere
• Candida albicans causes Candidiasis, thrush
• Skin lesions: vulvovaginitis, otomycosis, onychomycosis
• Also, C. glabrata, C. lusitaniae

• LSD synthesized from this fungus
• Intensifies sense perceptions
• MOA: Blocking serotonin function in the brain