A Preliminary Study of Germicidal Efficacy against Candida auris

Abstract

Background

Candida auris is an emerging fungal pathogen that is often resistant to major classes of antifungal drugs and can survive on healthcare environmental surfaces, and is now a serious global health threat. It remains unclear whether C. Auris is also resistant to germicides (e.g., disinfectants, antiseptics). In this study, we investigated germicidal activity against C. Auris.

Methods

We assessed 21 different germicides plus 2 dilutions of sodium hypochlorite for C. Auris, Candida albicans, and Staphylococcus aureus. The disc-based quantitative carrier testing was performed to evaluate the germicidal activity of chemical germicides. An inoculum containing approximately 10⁶ test organisms with 5% fetal calf serum (FCS) was placed on each disk. The dried inoculum was exposed to the test germicide for 1 minute exposure time at room temperature then neutralized. The log₁₀ reduction of the test organism for each biocide was calculated and compared with mean carrier control counts.

Results

Efficacy of germicides with active ingredient, product name, and classification against C. Auris, C. Albicans, and S. Aureus is provided in Figure 1. Our germicidal study demonstrated at least 3-log₁₀ reduction (12/22, 55%) and 2-log₁₀ reduction (15/22, 68%) for C. Auris, 3-log₁₀ reduction (14/22, 64%) and 2-log₁₀ reduction (17/22, 77%) for C. Albicans, and 3-log₁₀ reduction (22/22, 100%) for S. Aureus in the challenging test conditions (5% FCS and 1 minute exposure time). C. Auris was less susceptible to 0.55% ortho-phthalaldehyde, 2% chlorhexidine gluconate, 4% chlorhexidine gluconate, and 1% chloroxylenol compared with C. Albicans or S. Aureus. C. Auris was more susceptible to 70% ethanol, compared with C. Albicans. Several germicides (21.7% quaternary ammonium compounds [QAC], 3% hydrogen peroxide, 5.25% sodium hypochlorite [1:50 dilution], 0.5% triclosan) had <2-log₁₀ reduction for both C. Auris and C. Albicans.

Conclusion

Our preliminary study results suggest that many germicides commonly used in healthcare facilities are effective against C. Auris, but further evaluations are warranted (e.g., QAC, triclosan, chlorhexidine gluconate, hydrogen peroxide) under less challenging test conditions (e.g., without 5% FCS and/or longer exposure time).

Disclosures

D. J. Weber, PDI: Consultant, Consulting fee.