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Candidiasis |
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- Candida albicans is a classic opportunistic pathogen.
- Can cause, cutaneous, mucocutaneous, or systemic infections
- Normal flora of animals and humans
- Considered to be a yeast, but can form pseudohyphae and short hyphae.
- Tissue invasion often associated with hyphal formation
- Other species: C. tropicalis, C. parapsilosis
Avian disease
- Invasion of mucosa of upper g.i. tract
- Forms raised lesions, can slough and ulcerate
- Related to poor sanitation
Swine
- Cutaneous infection
- Esophageal and stomach infection
Cattle
- Mastitis
- Usuaully species other than C. albicans
- Result of contaminated infusion cannula
- Rumenitis
- Following antibiotic treatment or rapid shift in diet
Dogs and cats
- Cutaneous infection - occlusive dressings
Marine mammals
- skin infections
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Human Candidiasis |
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Cutaneous infection
- Skin folds - constant moisture
- Infection of nail or nail bed
Mucosal or mucocutaneous infection
- Oral infection - "thrush"
- Overgrowth of flora - vaginitis, g.i. infection
- Chronic
- immunosuppression, AIDS
Systemic infection
- kidney, endocarditis
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Predisposing factors |
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- Youth: underdeveloped flora, immune system
- Physiological changes: pregnancy, steroids
- Broad-spectrum antibiotics: yeast overgrowth
- Underlying immune defect
- Poorly controlled diabetes
- Poor sanitation or hygiene: excessive moisture, dressings not changed regularly
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Virulence Mechanisms |
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- Adherence to mucosal surface
+ Related to ability to bind host glycoproteins?
+ iC3b, fibronectin, laminin, etc..
- Ability to form hyphae
- Thigmotropism - tendency to penetrate between cells
- Lytic enzymes
- Phenotypic switching -rapid, environmental
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Host Defense |
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- Antibodies present - little role in protection
- CMI - defect leads to disease
- Macrophages: activation increases killing
- PMNs: prevent systemic infection
- Killing mechanisms
- Intracellular yeast - can grow out of phagocyte
- Extracellular killing: ROI, RNI, defensins
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Treatment |
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Cutaneous or mucosal infection
- Crystal violet
- Clotrimazole (i.e.. Lotrimin), miconazole
- Nystatin
Systemic infection
- Amphotericin B
- Ketoconazole, fluconazole
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Diagnosis |
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- Direct microscopic examination
- Visualize mixture of hyphae and yeast
Culture
- Grows well on Sabouraud’s agar
- colonies in 24-48 hr at 25 or 37 C
Differentiation of C. albicans
- Germ-tubes - 2- 4 hr incubation in plasma
- Chlamydospores - inoculate cornmeal agar
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