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UV-C disinfection more effective against MRSA than C. auris
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Using mobile ultraviolet-C light room decontamination devices was significantly less effective in reducing Candida auris and other Candida species than in reducing MRSA, according to recent findings.
“These devices are effective in killing vegetative bacterial pathogens, and with sufficient exposure, they are effective against Clostridium difficile spores,” Curtis J. Donskey, MD, professor of medicine at Case Western Reserve University and staff physician in the infectious diseases section at Louis Stokes Cleveland VA Medical Center, and colleagues wrote. “Although there is evidence that UV-C is effective against C. albicans, no published studies have reported the efficacy of room decontamination devices against Candida species.”
Researchers sought to determine whether a UV-C room decontamination device would be as effective in killing strains of C. auris, C. albicans and C. glabrata as killing strains of MRSA and C. difficile spores.
For each pathogen, Donskey and colleagues spread 10-µL aliquots containing 106 log10 colony-forming units in phosphate-buffered saline with 5% fetal calf serum over 10-, 20- or 40-mm diameter circular stainless-steel carriers, then allowed them to air dry for 30 minutes. They placed each carrier perpendicular to the vertical lamps, located 5 feet away from the device at a height of 4 feet, exposing them to a UV-C cycle of 10 minutes. With one strain of each pathogen, they conducted additional experiments on 20-mm-diameter disks at exposure times of 10, 20 and 30 minutes. They performed a two-way analysis of variance, comparing the mean log reductions for the different types of pathogens.
Laboratory testing revealed a reduction in MRSA after 10 minutes of UV-C exposure for each disk size, which was significantly greater than the reduction in each of the Candida species and C. difficile spores (P < .001). Spreading the same inoculum of C. difficile spores and Candida species over increasing disk sizes caused a surge in log reductions for the 40-mm compared with the 10-mm diameter disks (P < .01). Increasing the cycle time to 20 or 30 minutes for each of the Candida species and C. difficile spores resulted in greater reductions in recovery (P < .001), whereas MRSA was reduced by more than 6 logs at each exposure time. Although C. auris was reduced less than C. glabrata and C. albicans with the 10-minute exposure, all three Candida species showed similar reductions after the 20- and 30-minute exposure times (P > .05).
“Ultraviolet light was significantly less effective against Candida species, including the emerging pathogen C. auris, than against MRSA. The take-home message from our study is that standard cleaning should continue to be emphasized for control of Candida,” Donskey told Infectious Disease News. “Bleach and improved hydrogen peroxide disinfectants are very effective against Candida, whereas quaternary ammonium disinfectants have relatively poor activity. If ultraviolet light decontamination devices are used, our results suggest that longer cycle times may be beneficial.” – by Savannah Demko
References:
Cadnum JL, et al. Infect Control Hosp Epidemiol. 2017;doi:10.1017/ice.2017.162.
Cadnum JL, et al. Infect Control Hosp Epidemiol. 2017;doi:10.17/ice.2017.239.
Disclosures: Donskey reports serving on an advisory board for 3M and receiving research grants from Merck, GOJO, STERIS and EcoLab. All other authors report no relevant financial disclosures.