Under the Microscope with Bill Rutala: Inactivation of Candida auris by Ultraviolet-C.

Author: Dr. William A. Rutala, PhD, MPH, CIC

December 7, 2021

Inactivation of Candida auris and Candida albicans by ultraviolet-C. authored by Rutala WA, Kanamori H, Gergen MF, Sickbert-Bennett EE, Weber DJ1 addresses the ability of UV-C  to inactivate C. auris.

Candida auris is an emerging fungal pathogen that is often resistant to major classes of antifungal drugs. It is a serious global health threat and has caused severe infections with frequent mortality in many countries. C. auris can survive on healthcare environmental surfaces for at least 7 days and cause outbreaks in healthcare facilities. These findings suggest that C. auris has an environmental route of transmission. Thus, infection prevention strategies, such as surface disinfection and room decontamination technologies (e.g., ultraviolet-C) , are essential to control transmission. In this study, a UV-C device (Tru-D SmartUVC, LLC. Memphis, TN) was evaluated for its antimicrobial activity against C. auris and C. albicans.1

There is no standard level of germicidal efficacy for environmental surfaces, but a log10 reduction of at least 3-log10 (or 99.9% reduction) is likely to be clinically effective against C. auris in preventing environmental transmission. The UV-C room decontamination unit tested achieved an overall 2.93-log10 reduction of C. auris (Antibiotic Resistance Bank #0385 strain) with fetal calf serum (FCS) and an overall 2.48-log10 reduction of C. auris without FCS. C. auris had a lower log10 reduction than C. albicans. Direct UV-C, with or without FCS (log10 reduction 4.57 and 4.45, respectively), had a higher log10 reduction than indirect UV-C for C. auris (log10 reduction 2.41 and 1.96, respectively), which was statistically significant. The vertical UV-C (i.e., perpendicular to UV light) had statistically higher log10 reductions than horizontal UV (i.e., flat on surface) against C. auris and C. albicans with FCS and without FCS. For example, for C. auris with FCS the log10 reductions for vertical surfaces were 4.92 and for horizontal surfaces, the log10 reductions were 2.87.

This study and other studies2 demonstrated that C. auris can be inactivated on environmental surfaces so long as factors that affect inactivation are optimized (e.g., exposure time, distance, UV-C intensity). In our investigation, the UV-C device was set on the bacterial cycle (12,000 µWs/cm2) and the device operated for 17-19 minutes. Cadnum and associates2 suggested that longer cycles (i.e., sporicidal) may be beneficial, as has been recommended for some UV-C devices in C. difficile contaminated rooms. These data and other published UV-C studies should be used in developing cycle parameters that prevent contaminated surfaces from being a source of acquisition by staff or patients of this globally emerging pathogen.

Disclosure: Dr. Rutala is a consultant for PDI.

1Rutala WA, Kanamori K, Gergen MF, Sickbert-Bennett EE, Weber DJ. 2021 Inactivation of Candida auris and Candida albicans by ultraviolet-C. Infect Control Hosp Epidemiol.doi: https://doi.org/10.1017/ice.2021.214

2Cadnum JL, Shaikh AA, Piedrahita CT, Jencson AL, Larkin EL, Ghannoum MA, et al.  Relative resistance of the emerging fungal pathogen Candida auris and other Candida species to killing by ultraviolet light. Infect Control Hosp Epidemiol 2018;39:94-96. doi: 10.1017/ice.2017.239. Epub 2017 Nov 21.



Dr. William A. Rutala, PhD, MPH, CIC PhD, MPH, CIC
Dr. William Rutala PhD, MPH, CIC Professor in the Division of Infectious Diseases and Director, Statewide Program for Infection Control and Hospital Epidemiology (SPICE).


Dr. Bill Rutala is the Director and co-founder of the Statewide Program for Infection Control and Epidemiology and a Professor for the Division of Infectious Diseases at the University of North Carolina’s School of Medicine.  He was the Director of Hospital Epidemiology, Occupational Health and Safety Program at the University of North Carolina Hospitals for 38 years before retiring in May 2017.

He is a retired Colonel with the U.S. Army Reserve and is certified in infection control.  He has been an advisor to the Centers for Disease Control and Prevention (a former member of the Healthcare Infection Control Practices Advisory Committee [HICPAC], 1999-2003), the Food and Drug Administration (a former member of the General Hospital and Personal Use Devices Panel), the U.S. Environmental Protection Agency (a member of the Scientific Advisory Panel on Antimicrobial Research Strategies for Disinfectants) and the Federal Trade Commission.  Dr. Rutala is a member of various committees on the local, state, national, and international level as well as several professional societies including the American Society for Microbiology, Association for Professionals in Infection Control and Epidemiology (APIC), and the Society of Healthcare Epidemiology of America (SHEA).  He has served or currently serves on the three peer-reviewed journals on infection prevention in the world (i.e., Infection Control and Hospital Epidemiology, American Journal of Infection Control, and The Journal of Hospital Infection)

He has more than 650 publications (peer-review articles, books, book chapters, brief reports) in the fields of disinfection and sterilization (to include several guidelines such as the CDC Guideline for Disinfection and Sterilization in Healthcare Facilities) and epidemiology and prevention of healthcare-associated infections. Dr. Rutala has also been an invited lecturer at over 400 states, national and international conferences (in over 40 states and 40 countries) and has testified twice before the U.S. Congress.  Dr. Rutala earned his Bachelor of Science degree in science from Rutgers University, his master’s degree in microbiology from the University of Tennessee, and both his master’s in public health and a doctorate in microbiology from the University of North Carolina School of Public Health.

His contributions to infection prevention have been acknowledged by professional organizations with the following awards:  Carole M. DeMille Lifetime Achievement Award (APIC, 1999), Lowbury Lecture (Healthcare Infection Society, Scotland, 2002), Hygiene Medal (Rudolf Schulke Foundation, Germany, 2013), Larson Lectureship Award (APIC, 2012), SHEA Lectureship (SHEA, 2012), Barr Distinguished Alumni Award (UNC School of Public Health, 2012), Kelsey Lecture (the United Kingdom, 2001 and 2012), Crawford Award (lifetime achievement, OSAP, 2008), and Favero Lectureship (APIC, 2009). Dr. Rutala has a “named” award in his honor from two international infection prevention professional societies …APIC (William A. Rutala Research Award) and SHEA (William A. Rutala Scholarship).

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