Effective Disinfectants forCoccidioides ImmitisandC. posadasii

Abstract

The lack of published data on effective disinfectants and contact times for use on the fungal pathogens Coccidioides immitis and C. posadasii prompted the authors to investigate the fungicidal activity of three commonly used laboratory disinfectants on arthroconidia harvested from C. immitis strain 2009. They tested the ability of 10% bleach, 70% ethanol, and Vesphene® IIse to inactivate 107 arthroconidia in an aqueous suspension within 1, 2, 5, 10, or 20 minutes of contact time. Both 10% bleach and 70% ethanol provided a 7-log10 reduction in arthroconidia in less than 1 minute, with no growth observed at any of the tested time points. Vesphene® IIse was less effective, providing a 6-log10 reduction in arthroconidia after 5 minutes, but was unable to completely inactivate all of the arthroconidia, even after 20 minutes of contact time.

Evaluation of Virex® II 256 and Virex® Tb as Disinfectants of the Dimorphic FungiCoccidioides immitisandCoccidioides posadasii

“…Several attempts were made to perform 1-minute disinfectant evaluations in this study, but we were unable to safely and accurately perform the procedures within precisely 1 minute due to technical constraints of our centrifuge. These results differ from the Vogler et al 1 study, which found that 10% bleach and 70% ethanol were equally as effective in inactivating 1 × 10 7 arthroconidia within a 1-minute contact time. It is unlikely that the different bleach formulations used between the 2 studies brought about these differences, as the formulation used by Vogler et al 1 includes 6% sodium hypochlorite, whereas our study used an 8.3% sodium hypochlorite formulation.…”

“…These results differ from the Vogler et al 1 study, which found that 10% bleach and 70% ethanol were equally as effective in inactivating 1 × 10 7 arthroconidia within a 1-minute contact time. It is unlikely that the different bleach formulations used between the 2 studies brought about these differences, as the formulation used by Vogler et al 1 includes 6% sodium hypochlorite, whereas our study used an 8.3% sodium hypochlorite formulation. The most likely explanation for the differing results of 10% bleach efficacy is that our study evaluated the disinfectants against a 5-fold higher concentration of arthroconidia.…”

“…strains between the 2 studies. Our study used the C immitis strain RS and C posadasii strain Silveira, whereas Vogler et al 1 used C immitis strain 2009. The potential for the same disinfectants to have different inactivation efficacies dependent on strain, harvesting condition, or storage condition is interesting and warrants further investigation.…”

“…With regards to the dimorphic fungal pathogen Coccidioides posadasii, no study evaluating the efficacy of common disinfectants has been published in over 50 years, and only one study evaluating Coccidioides immitis has been published within the same time period. 1 The published study evaluated 10% bleach, 70% ethanol and a phenolic compound, Vesphene® IIse against the highly infectious spore form of the fungus. These authors found that 10% bleach and 70% ethanol were effective in providing a 7-log 10 reduction in fungal arthroconidia of Coccidioides immitis strain 2009 in less than 1 minute, whereas Vesphene® Iise was less effective, providing only a 6-log 10 reduction of arthroconidia within a longer contact time of 5 minutes.…”

Proper Care and Feeding of Coccidioides: A Laboratorian's Guide to Cultivating the Dimorphic Stages of C. immitis and C. posadasii

“…We recommend wearing Tyvek sleeves (Kimberly-Clark) when harvesting arthroconidia to further reduce this risk. We have previously shown that Coccidioides can be inactivated using 70% ethanol for 2 min or fresh 10% bleach for 2 min (Vogler, Nottingham, Parise, Keim, & Barker, 2015). Other researchers report effective use of Virex and report issues with 70% ethanol (Mitchell, Magee, Grys, & Lake, 2019).…”