This web text will specifically focus on Candida albicans but may briefly reference other Candida species.
1
Background / History
- Candida albicans, (yeast) accounts for up to 90% of superficial candidosis which can involve the nails and skin plus the mucous membranes of the mouth and vagina.
- There are a number of other species of Candida which also cause superficial candidosis but they will not be covered in detail in this text.
- C. albicans is a commensal and can be seen along with other commensal flora of the vagina, mouth, skin and gastrointestinal tract, etc.
- As a person gets older the carriage rate of C. albicans normally increases and the incidence of patients with Candida in hospital is higher than the incidence of persons in the general population.
- Pregnant woman also show a higher incidence of candidosis owing to their lowered immunity during pregnancy.
- A patient who has contracted a disease which may have lowered their immunity can cause the C. albicans to become an opportunistic pathogen.
- Uncontrolled and indiscriminate use of antibiotics which alter the body's normal flora can directly lead to overgrowth of yeast.
2
Classification
Classification
C. albicans
Kingdom Fungi
Phylum Ascomycota
Subphylum Saccharomycotina
Class Saccharomycetes
Order Saccharomycetales
Family Saccharomycetaceae
Genus Candida
Species Candida albicans
3
Morphology
- Morphology of C. albicans can be; Yeast like, filamentous or it can produce pseudohyphae, ( elongated cells linked together ). See Fig.1.
- Pseudohyphal formation is a type of budding where hypahe elongate and remain attached to the mother cell.
- Dimorphic - C. albicans can exist in either a mycelial state or a yeast state depending on growth conditions.
Fig.1 Gram stained Candida albicans (yeast)
REPLICATION
- All fungi reproduce by asexual mechanisms but not all fungi reproduce sexually;
a) Anamorph - fungal asexual reproduction
b) Telomorph - fungal sexual reproduction
- The above terms a and b are mainly used for classification purposes, for example, the organism is given different names depending on whether it is in an Anamorphic state phase or a telomorphic phase. This ruling applies to all fungal organisms including C. albicans.
- Clinically, fungal organisms are referred to by their anamorphic state name.
4
Pathogenesis
IMMUNITY
- Innate Immunity - Evidence suggests that the body has a strong innate immunity to C. albicans infections especially in healthy individuals.
- Humoral / Cell mediated immunity - these are two processes that are also responsible for immune protection against Candida infection. Cell mediated immunity is generally more important than other immune defence mechanisms against C. albicans.
- Serum antibody - The human host produces antibody to the cell wall of C. albicans
5
Clinical Disease
- As well as C. albicans, other Candida species are responsible for localised skin and nail disease
- Mucosal infection sites - Skin, mouth, vagina, bronchi within the lungs and the oesophagus.
- Below is a list of sites that can become infected with C. albicans plus a list of resulting diseases.
SYSTEMIC
Pulmonary infection, endocarditis, UTI, Endopthalmitis, menningitis
CUTANEOUS
Paronchia, onycomycosis
MUCOCUTANEOUS
Thrush, perianal disease
CHRONIC
Granulomatous diease, mucocutaneous candidiasis.
- Some causes of C. albicans infections are as follows;
a) Immunosupression - diabetes melitus, burns, intravascular catheter, IVDA's
b) Mechanical - Occlusion, trauma
c) Other - AIDS, pregnancy, unchecked use of broad spectrum antibiotics.
6
Epidemiology
