Diagnosing Oral Yeast Infections
Primary Diagnostic Approach
- The Centers for Disease Control and Prevention recommends swabbing directly from the visible white plaques or lesions on the buccal mucosa, tongue surface, or oropharyngeal mucosa to diagnose oral candidiasis 1, 2, 3, 4
- The diagnosis of oropharyngeal candidiasis is typically clinical based on appearance alone, but when laboratory confirmation is needed, proper specimen collection is essential, as stated by the MMWR Recommendations and Reports 5
Optimal Swabbing Sites
- The American Dental Association suggests targeting the creamy white, plaque-like lesions on the buccal mucosa, tongue surface, or oropharyngeal mucosa for swabbing 5
- For erythematous candidiasis (without white plaques), swab the red patches on the palate or tongue, as recommended by the MMWR Recommendations and Reports 5
- Angular cheilosis at the corners of the mouth can also be swabbed if present, according to the MMWR Recommendations and Reports 5
Laboratory Processing
- The Infectious Diseases Society of America recommends inoculating swabs on selective fungal media to prevent overgrowth by colonizing oral bacteria 1, 2, 3, 4
- Request potassium hydroxide (KOH) preparation for immediate microscopic examination to visualize yeast forms and pseudohyphae, as suggested by the MMWR Recommendations and Reports 5
When to Obtain Laboratory Confirmation
- The American College of Physicians recommends laboratory testing for recurrent or complicated cases requiring species identification and antifungal susceptibility testing 1, 2, 3, 4
- Laboratory testing should be pursued in cases of prior azole exposure where resistance patterns need assessment, as stated by the Clinical Microbiology and Infection 1, 2, 3, 4
- Treatment failures should be investigated with laboratory testing to identify non-albicans species (particularly C. glabrata) which may be refractory to standard therapy, according to the MMWR Recommendations and Reports 5
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, as noted by the MMWR Recommendations and Reports 5
- Microscopy will show budding yeast cells and pseudohyphae in most cases, according to the MMWR Recommendations and Reports 5
- Note that C. glabrata does not form pseudohyphae, so only yeast cells may be visible, as stated by the Clinical Microbiology and Infection 1, 2