infection control & hospital epidemiology october 2017, vol. 38, no. 10 concise communication
Effectiveness of Disinfectants Against Candida auris and Other Candida Species
Jennifer L. Cadnum, BS;1 Aaron A. Shaikh, BS;2 Christina T. Piedrahita, BS;1 Thriveen Sankar, MBA;1 Annette L. Jencson, CIC;1 Emily L. Larkin, BS;3,4 Mahmoud A. Ghannoum, PhD;3,4 Curtis J. Donskey, MD2,5
Contaminated surfaces are a suspected source for dissemination of the globally emerging pathogen Candida auris. In laboratory testing, sporicidal and improved hydrogen peroxide disinfectants were highly effective against C. auris, C. glabrata, and C. albicans. The widely used quaternary ammonium disinfectants exhibited relatively poor activity against all of the Candida species.
Infect Control Hosp Epidemiol 2017;38:1240–1243
Candida auris is a globally emerging pathogen that is often resistant to multiple antifungal agents.1–3 In several reports, C. auris has been recovered from the hospital environment, suggesting that contaminated surfaces may be a source of transmission.1,2 The Centers for Disease Control and Preven- tion (CDC) has therefore recommended daily and post- discharge disinfection of surfaces in rooms of patients with C. auris infection.4 Moreover, the use of an Environmental Protection Agency (EPA)–registered, hospital-grade disin- fectant effective against Clostridium difficile spores was specified.4 However, nonsporicidal disinfectants are widely used and many have an EPA-registered antifungal claim.5 No hospital disinfectants are registered for use specifically against C. auris, and it is not known whether C. auris is less susceptible to disinfectants than other Candida species.
methods
We evaluated the efficacy of 9 commercial disinfectants and the common household disinfectant white distilled vinegar (>5% acetic acid, pH 2.0) against C. auris, C. albicans, and C. glabrata. For comparison, 3 strains of methicillin-resistant Staphylococcus aureus (MRSA) were tested. The 5 C. auris strains have been described previously3,6; the strains included 3 multidrug-resistant clinical isolates (MRL#31102 and #31103 and CBS#12373) and 2 drug-susceptible isolates (CBS#10913 and CDC strain AR-BANK#0381). The 4 C. albicans strains included American Type Culture Collection (ATCC) strains SC#5314 and #10231 and 2 clinical strains from the Center for Medical Mycology, Cleveland, Ohio (MRL#32249 and #32708). The C. glabrata clinical strains were MRL#31820, #34870, and #9547. The 3 MRSA strains included ATCC strain 43,300 and 2 clinical isolates.
The disinfectants and their contact times are shown in
Table 1. For the commercial products, the contact times were based on the manufacturer’s recommendations except for Clorox Healthcare hydrogen peroxide cleaner disinfectant (ie, a 1-minute exposure was used rather than the 3 minutes recommended for C. albicans based on preliminary experi- ments that demonstrated excellent activity with the shorter exposure time). Testing of disinfectant efficacy was conducted according to the American Society for Testing and Materials (ASTM) Standard quantitative carrier disk test method (ASTM E2197-11).7 To simulate the presence of organic material, 5% fetal calf serum (Remel, Lenexa, KS) was added to the inocu- lum. The steel-disk carriers were inoculated with ~106 colony- forming units (CFUs) of washed Candida species or MRSA from an overnight culture; the test was not considered valid unless a minimum of 105 CFU was recovered from control carriers. After disinfectant exposure, carriers were neutralized with Dey-Engley neutralizer (Remel), except for Oxivir Tb (Diversey, Charlotte, NC) and Clorox Healthcare hydrogen peroxide cleaner disinfectant (Clorox, Oakland, CA), which were neutralized with 0.1% Tween 80 and 3% glycine in 0.85% NaCl. Serial dilutions were plated onto Sabouraud dextrose agar (Becton-Dickinson, Sparks, MD) and incubated at 37°C for 72 hours. Log reductions were calculated by subtracting viable organisms recovered after disinfectant exposure versus deionized water controls. Experiments were performed in triplicate. To determine whether different test methods might yield different results for a quaternary ammonium compound, we compared reductions of the Candida species and MRSA for Virex II 256 using ASTM E-2197-11 and the AOAC (Associ- ation of Official Agricultural Chemists) Official Method 961.02 for Germicidal Spray Products.8 For this comparison, we included tests with a lower inoculum resulting in 104 CFU recovered from control carriers. The rationale for testing the reduced inoculum was that the EPA product performance test guideline OCSPP 810.2200 for disinfectants with fungicidal claims recommends that carriers have a concentration of 104 to 105 CFU per carrier.9 In the AOAC method, glass micro- scope slides are used as carriers and the inoculum is spread to cover approximately 1 square inch. For all experiments, log reductions were compared for different disinfectants using linear modeling with post hoc Tukey’s adjustment for multiple comparisons. Data were analyzed using SPSS statistical soft- ware version 10.0 (SPSS, Chicago, IL).
results
Figure 1 shows the mean reductions for the disinfectants using the ASTM method. For MRSA, each of the disinfectants reduced recovery by ~6 log10 CFU. The data for each of the Candida species was pooled because there were no significant
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