Clinical characteristics and relevance of oral Candida biofilm in tongue smears

Dimorphic Candida exist as commensal yeast carriages or infiltrate hyphae in the oral cavity. Here, we investigated the clinical relevance of Candida hyphae in non-pseudomembranous oral candidiasis (OC) by smears of tongue biofilms. We conducted a retrospective study of 2829 patients who had had tongue smears regardless of OC suspicion. Clinical characteristics were evaluated using a novel method of assessing hyphae. Clinical factors (moderate/severe stimulated pain, pain aggravated by stimulation, tongue dorsum appearance and initial topical antifungal use) were highly significant in the high-grade hyphae group but were statistically similar in the low-grade hyphae and non-observed hyphae group, suggesting low-grade hyphae infection as a subclinical OC state. In addition to erythematous candidiasis (EC), a new subtype named “morphologically normal symptomatic candidiasis” (MNSC) with specific pain patterns and normal tongue morphology was identified. MNSC had a significantly higher proportion of moderate and severe stimulated pain cases than EC. Low unstimulated salivary flow rate (<0.1 mL/min) was found to be a common risk factor in MNSC and EC. In non-pseudomembranous OC, pain patterns were dependent on Candida hyphae degree regardless of tongue dorsum morphology.