Assessment of <i>Candida</i> Species Contamination on Dental Unit Surfaces: Prevalence, Risk Factors, and Infection Control Strategies

Abstract

Background: Cross-contamination in dental clinics poses a significant risk for microbial transmission, especially from opportunistic fungal pathogens such as Candida species. Among them, Candida albicans is a common commensal of the oral cavity, capable of causing opportunistic infections in immunocompromised individuals. Dental unit surfaces, including chair headrests, light handles, control panels, and saliva ejectors, may serve as reservoirs for Candida, facilitating its spread. Objectives: This study aimed to determine the prevalence of Candida species contamination on dental unit surfaces, assess antifungal resistance patterns, and evaluate the effectiveness of current infection control protocols. Methods: This cross-sectional study was conducted at Zanjan University of Medical Sciences in 2023. A total of 120 samples were collected from high-contact surfaces in 12 dental units at three time points: Before, during, and after clinical shifts. Culturing was performed on Sabouraud dextrose agar (SDA). Identification of isolates included gram staining, germ tube testing, and CHROMagar Candida. Antifungal susceptibility was assessed via the disk diffusion method based on Clinical and Laboratory Standards Institute (CLSI) M44-A2 guidelines. Descriptive and inferential analyses were conducted using SPSS v26. Results: Candida species were detected in 39.2% of all samples, with contamination rising significantly from 18.3% before shifts to 60.0% after shifts (P < 0.001). The most contaminated surfaces were chair headrests (72.5%) and light handles (65.8%). The predominant isolate was C. albicans, followed by C. glabrata and C. tropicalis. Fluconazole susceptibility in C. albicans was 85.1%, while amphotericin B and nystatin showed 96.7% efficacy. Despite routine disinfection, 39.2% of post-cleaning surfaces remained contaminated. Conclusions: This study highlights the persistence of Candida contamination on dental surfaces and potential shortcomings of routine disinfection protocols. It recommends enhanced sterilization practices — including UV sterilization, high-frequency surface cleaning, and personnel hygiene reinforcement — to reduce fungal transmission in clinical dentistry.