Distribution of Candida Species Causing Oral Candidiasis in High-Risk Populations: A Systematic Review

Background: In the last decade, infections caused by Candida species have increased. Although C. albicans remains the most predominant species, fungal infections caused by non-albicans Candida (NAC) species have also been rising. This study aimed to determine which Candida spp. are most frequently associated with oral candidiasis. Methods: In accordance with PRISMA guidelines, a literature search was conducted in the PubMed, Cochrane Library, and ScienceDirect databases. The search used the keyword combination "candida spp" AND "oral candidiasis" AND "oral isolates" and included articles published between 2013 and 31 October 2025. Results: A total of 658 articles were identified, of which 24 met the inclusion criteria. Across these studies, 12,750 isolates were reported. C. albicans was the most prevalent species, accounting for 81.7% of all isolates. NAC species were detected at lower frequencies, including C. tropicalis (7.2%), C. glabrata (4.5%), C. krusei (4.1%), C. parapsilosis (1.0%), C. dubliniensis (0.8%), C. kefyr (0.2%), C. guilliermondii (0.1%), C. lusitaniae (0.1%), and other rare or unidentified species (0.2%). The increasing prevalence of Candida infections is associated with a growing population of immunocompromised individuals, and treatment remains challenging due to rising antifungal resistance. Conclusions: Although C. albicans remains the most prevalent, the appearance of NAC species is gradually increasing. With the increase of Candida spp. resistant to conventional antifungal agents and with the competitive or synergistic interaction between Candida spp., it is necessary to develop new therapeutic approaches.