8. Lab diagnosis of Oral Candidiasis
Samples
• Whitish patches from mucous membrane of mouth
• Sputum
Method of collection
• Sterile swabs
Direct examination (Microscopy)
• KOH wet mount
• Gram staining ( Presence of yeast cells and pseudohyphae)
• Other stains: PAS and Gomori’s methenamine silver stain
9. Lab diagnosis continued…
Fungal culture
• Sabouraud Dextrose Agar + Antibiotics ( Cream, Pasty, Smooth colonies in 3-4
days of incubation at 37 C)
• Cornmeal Agar (Characteristic terminal chlamydospores, yeast cells and
pseudohyphae in clusters at 25 C)
• CHROMagar (light green to bluish green colonies)
Germ tube test (Reynold’s-Braude Phenomenon)
• Culture of candida treated with sheep/normal human serum is incubated at 37
C for 2-4 hours
• No constriction seen at the point of attachment to the yeast cell
• Appear in 2 hours for C.albicans
Chlamydospore formation
• Suspected strain of Candida isolates gron on CMA or rice starch agar and
incubated at 25 C
• Formation of large, highly refractile, thick walled, terminal chlamydospores in
2-3 days of incubation
10. Lab diagnosis continued…
Biochemical tests
• Glucose and Maltose fermented with acid and gas
production, sucrose and lactose not fermented.
• Pale pink coloration in Tetrazolium reduction medium
Typing of Candida strains
• Tests include serotyping and isoenzyme profiling
• RFLP and Southern blotting technique used
Immunodiagnosis
• PCR based tests for candida-DNA detection
• Detection of Candida albican-derived molecules
• ELISA, RIA, CIE, PHA and LPA
11. Lab diagnosis continued…
Detection of metabolites
• Detection of D-mannose and D-arabinitol in sera by gas
liquid chromatography
• G-test for detection of glucan
Skin tests
• Testing delayed hypersensitivity to candidial antigens
Animal Pathogenicity
• Tests on rabbits and mice for susceptibility to different
candidia species