Probiotics for the prevention and treatment of oral candidiasis: a systematic review and meta-analysis

Oral candidiasis is a common opportunistic fungal infection, and increasing antifungal resistance has encouraged the investigation of alternative therapeutic approaches, including probiotics. This systematic review and meta-analysis evaluated the effects of probiotics on microbiological outcomes related to the prevention and treatment of oral candidiasis in adults, either as monotherapy or as an adjunctive intervention. A comprehensive search of four databases (PubMed/MEDLINE, Cochrane Library, ClinicalTrials.gov, and Web of Science) yielded 15 eligible randomized clinical trials, all of which were included in the meta-analysis. Risk of bias was assessed using the Cochrane Risk of Bias 2.0 tool, and the certainty of the evidence was evaluated using the GRADE approach. Meta-analyses were performed using Review Manager Web. Primary outcomes included persistent oral Candida colonization (positive culture following intervention) and post-intervention Candida counts. The meta-analysis showed a 41% lower prevalence of oral Candida colonization among individuals treated with probiotics compared to controls. Probiotics also significantly decreased mean Candida counts post-intervention. Subgroup analyses showed no significant differences according to clinical purpose (prevention versus treatment) or treatment strategy (monotherapy versus adjunctive therapy). However, a high level of heterogeneity was observed (I² = 72–98%) across studies that varied in study design, probiotic strains, dosages, administration methods, and follow-up periods. Importantly, both meta-analyses evaluated microbiological outcomes rather than clinically diagnosed oral candidiasis. Safety data were inconsistently reported, although no serious probiotic-related adverse events were identified. According to the GRADE framework, the certainty of the evidence ranged from low to very low. Current evidence suggests that probiotics may reduce oral Candida colonization and fungal burden in adult populations. However, because the available evidence is primarily based on microbiological outcomes and highly heterogeneous studies, their effect on clinically meaningful outcomes, including clinical resolution of oral candidiasis, remains uncertain. Further well-designed randomized controlled trials with standardized clinical and microbiological outcomes are required. Probiotics may reduce oral Candida colonization and fungal burden. However, current evidence primarily supports microbiological effects, and their clinical relevance remains uncertain.