Candida

Question 1

1) Classification

Answer 1

Kingdom: Fungi
Family: saccharonycetaceae
Genus: Candida
Species: albicans

Question 2

2) morphology

Answer 2

• oval gram positive budding yeast cells
• forms pseudohyphae when the buds continue to grow without detaching
• C.albicans is dimorphism, can be:
  Yeast (harmless)
  Pseudohyphae
  True hyphae (pathogenic)

Question 3

3) growth characteristics

Answer 3

• obligate aerobes
• growth in moist area
• body temperature
• neutral pH
• commensal organisms in the gut, genital and lungs

Question 4

4) antigenic structure

Answer 4

Principal cell wall polymers:

• mannans
• gluccans

Question 5

5) virulence factors

Answer 5

• adherence to host tissues (epithelium or endothelium)
• cytolytic enzymes (proteinases and phospholipases)
• hydrophobicity
• variable phenotypic expression
• morphologic switching

Filamentous forms is believed to facilitate adhesion and penetration of epithelium

Question 6

6) disease

Answer 6

• cutaneous and mucosal candidiasis
• systemic candidiasis (immunocompromised)
• chronic mucocutaneous candidiasis (occur in children with T-cell defect in immunity to Candida)

Question 7

7) microbiological diagnosis

Answer 7

DME:
>gram-staining: gram positive budding cells; budding cells in chain (pseudohyphae)

Culture:

Sabouraud’s agar:
Raised, cream coloured opaque colonies

> chromagar Candida: presumptive identification

Specific tests:

• Germ tube formation
• Production of chlamydospores

Question 8

7) treatment and prevention

Answer 8

Local infection:

Oral or topical clotrimazole or nyastatin

Systemic infection:

Amphotericin B with flucytosine