Red/Orange Autofluorescence in Selected Candida Strains Exposed to 405 nm Laser Light

BACKGROUND

Candida albicans and similar species are significant pathogens in immunocompromised and hospitalized individuals, known for mucosal colonization and bloodstream/organ invasion. Many pathogenic fungi, including these species, exhibit autofluorescence (R/OF) under specific light conditions, a feature crucial for their detection.

AIM

We investigated the use of a 405 nm diode laser for the direct observation of red/orange autofluorescence of Candida spp., common in the oral cavity, exploring its potential in health screenings.

METHODS

This study utilized cultures of Candida spp. on Sabouraud dextrose agar with Qdot 655 and 685 for fluorescence benchmarking, illuminated using a 405 nm diode laser (continuous wave, power 250 mW, 0.0425 J/cm² fluence, 0.0014 W/cm² power density). Images were captured using a yellow-filter camera at set intervals (48 to 144 h). Visual and computational analyses evaluated the R/OF in terms of presence, intensity, coloration, and intra-colony variation.

RESULTS

Most Candida strains displayed red/orange autofluorescence at all observation times, characterized by varied coloration and intra-colony distribution. Initially, there was an increase in R/OF intensity, which then stabilized in the later stages of observation.

CONCLUSIONS

The majority of the Candida strains tested are capable of emitting R/OF under 405 nm laser light. This finding opens up new possibilities for integrating R/OF detection into routine dental screenings for Candida spp.