Diagnosing Oral Yeast Infections: Swabbing Technique
Swab directly from the visible white plaques or lesions on the buccal mucosa, tongue surface, or oropharyngeal mucosa to diagnose oral candidiasis. 1
Primary Diagnostic Approach
The diagnosis of oropharyngeal candidiasis is typically clinical based on appearance alone, but when laboratory confirmation is needed, proper specimen collection is essential. 1
Optimal Swabbing Sites
- Swab the lesion itself - the essential specimen is a swab taken directly from the visible white plaques or affected areas 1
- Target the creamy white, plaque-like lesions on the buccal mucosa, tongue surface, or oropharyngeal mucosa 1
- For erythematous candidiasis (without white plaques), swab the red patches on the palate or tongue 1
- Angular cheilosis at the corners of the mouth can also be swabbed if present 1
Laboratory Processing
- Inoculate swabs on selective fungal media to prevent overgrowth by colonizing oral bacteria 1
- Request potassium hydroxide (KOH) preparation for immediate microscopic examination to visualize yeast forms and pseudohyphae 1, 2
- Culture on Sabouraud dextrose agar is the standard method for confirming Candida species 2
When to Obtain Laboratory Confirmation
While clinical diagnosis is usually sufficient, laboratory testing should be pursued in specific scenarios:
- Recurrent or complicated cases requiring species identification and antifungal susceptibility testing 1
- Prior azole exposure where resistance patterns need assessment 1
- Atypical presentations that require differentiation from other oral lesions 2
- Treatment failures to identify non-albicans species (particularly C. glabrata) which may be refractory to standard therapy 1
Key Diagnostic Features
- The distinguishing characteristic of oral candidiasis is that white plaques can be scraped off with a tongue depressor, unlike oral hairy leukoplakia 1
- Microscopy will show budding yeast cells and pseudohyphae in most cases 1, 2
- Note that C. glabrata does not form pseudohyphae, so only yeast cells may be visible 1
Common Pitfalls to Avoid
- Do not swab normal-appearing mucosa - this will only detect colonization, not infection, as Candida is present in 53% of healthy individuals 2
- A biopsy is not mandatory for routine diagnosis but may help discriminate between infection and colonization in unclear cases 1
- Biopsy should be obtained in hyperplastic candidiasis or lesions responding poorly to treatment to rule out malignant changes 2, 3