Aerosolized Hydrogen Peroxide Decontamination of N95 Respirators, with Fit-Testing and Virologic Confirmation of Suitability for Re-Use During the COVID-19 Pandemic

T. Hans Derr; Melissa A. James; Chad V. Kuny; Prem P. Kandel; Matthew D. Beckman; Kevin L. Hockett; Mark A. Bates; Moriah L Szpara

Inoculation of phi6 bacteriophage onto respirator facepieces followed the same approach as for other viruses (described above). However, phi6-inoculated respirator pieces were resuspended in 250 µL of King's medium B (KB). These were then quantified on lawns of Pseudomonas syringae pathovar phaseolicola strain 1448A (Pph) using a previously described soft agar overlay protocol (14) . Briefly, 100 µl logarithmic culture of Pph (OD600 ~ 0.5) and 100 µl of the phage preparation were sequentially added to 3 ml of molten soft agar (0.7%) maintained at 55ºC. The mixture was quickly poured on top of a KB agar plate and dried in the biosafety cabinet before transferring to a 28ºC incubator. Alternatively, for enumeration of "inoculum" and "dried" samples, soft agar Pph lawns were prepared and 10 µl dilutions of phage preparation were spotted. Plaque forming units (PFU) were enumerated after 24-48 hours of incubation at 28ºC.