Evaluation of Virex® II 256 and Virex® Tb as Disinfectants of the Dimorphic Fungi Coccidioides immitis and Coccidioides posadasii

Introduction: To date, limited published data exists regarding the efficacy of commonly used disinfectants in inactivating the Risk Group 3 dimorphic fungal pathogens, Coccidioides immitis and Coccidioides posadasii. Newer generation quaternary ammonium compounds, like Virex® II 256 and Virex® Tb, have not been previously evaluated. Methods: Herein, these disinfectants are evaluated against 10% bleach and 70% ethanol, for their ability to inactivate 5 × 10 ⁷ arthroconidial spores of C immitis RS or C posadasii strain Silveira within 2, 5, 10 or 20 minutes contact time in aqueous solution. Results: Evidence is provided that both Virex® II 256 and Virex® Tb are highly effective alternatives to 10% bleach or 70% ethanol for the disinfection of 5 × 10 ⁷ arthroconidia of Coccidioides spp. within 2 minutes of contact time. Discussion: Both 70% ethanol and 10% bleach were seen as less effective than the other disinfectants, requiring a longer contact time to completely inactivate the same number of arthroconidia. Conclusion: A contact time of > 2minutes is adequate for the disinfection of 5 × 10 ⁷ Coccidioides spp. arthroconidia when using either the Virex® II 256 and Virex® Tb formulations.