Candida albicans is a dimorphic fungus, i.e. it can take two
forms. Most of the time it exists as oval, single yeast cells, which
reproduce by budding. Most yeasts do not produce mycelia (a mass of branching,
threadlike hyphal filaments), but Candida has a trick up its sleeve.
Normal room temperatures favour the yeast form of the organism, but under physiological
conditions (body temperature, pH, and the presence of serum) it may develop
into a hyphal form. Pseudohyphae, composed of chains of cells, are also
common. In the video, you can see yeast cells and a few elongated cells which
have begun to grow into a hypha:
There are many species of the genus Candida which cause the disease
known as candidiasis or "thrush". Candida is a commensal
organism found in 40-80% of normal humans, and is present in the mouth, gut,
and vagina. Problems start when a person experiences some alteration in:
Cellular immunity: e.g. immunosuppression or AIDS
Normal body flora: e.g. loss of normal bacterial flora due to
antibiotic or steroid therapy
Normal physiology: e.g. cardiac surgery or indwelling catheters
Although
Candida most frequently infects the skin and mucosal surfaces, it can
cause systemic infections manifesting as pneumonia, septicaemia or endocarditis
in severely immunocompromised patients. There does not appear to be significant
difference in pathogenic potential of different Candida strains, therefore
establishment of infection appears to be determined by host factors and not the
organism itself. However, the ability to assume various forms may be related
to the pathogenicity of the organism. The yeast form is 10-12 µm in diameter.
Pseudohyphae (chains of cells) may be formed from budding yeast cells which remain
attached to each other. Chlamydospores may be formed on the
pseudomycelium. Fortunately, several drugs are available to treat serious systemic
infections, e.g. itraconazole and fluconazole.
Although
Candida most frequently infects the skin and mucosal surfaces, it can
cause systemic infections manifesting as pneumonia, septicaemia or endocarditis
in severely immunocompromised patients. There does not appear to be significant
difference in pathogenic potential of different Candida strains, therefore
establishment of infection appears to be determined by host factors and not the
organism itself. However, the ability to assume various forms may be related
to the pathogenicity of the organism. The yeast form is 10-12 µm in diameter.
Pseudohyphae (chains of cells) may be formed from budding yeast cells which remain
attached to each other. Chlamydospores may be formed on the
pseudomycelium. Fortunately, several drugs are available to treat serious systemic
infections, e.g. itraconazole and fluconazole.