Effect of five decontamination methods on face masks and filtering facepiece respirators contaminated with Staphylococcus aureus and Pseudomonas aeruginosa

Abstract
Introduction. In the context of the global pandemic due to SARS-CoV-2, procurement of personal protective equipment during the crisis was problematic. The idea of reusing and decontaminating personal surgical masks in facilities was explored in order to avoid the accumulation of waste and overcome the lack of equipment.
Hypothesis. Our hypothesis is that this work will show the decontamination methods assessed are effective for bacteria, such as Staphylococcus aureus and Pseudomonas aeruginosa.
Aim. We aim to provide information about the effects of five decontamination procedures (UV treatment, dry heat, vaporized H2O2, ethanol treatment and blue methylene treatment) on S. aureus and P. aeruginosa. These bacteria are the main secondary bacterial pathogens responsible for lung infections in the hospital environment.
Methodology. The surgical masks and the filtering facepiece respirators were inoculated with two bacterial strains (S. aureus ATCC 29213 and P. aeruginosa S0599) and submitted to five decontamination treatments: vaporized H2O2 (VHP), UV irradiation, dry heat treatment, ethanol bath treatment and blue methylene treatment. Direct and indirect microbiology assessments were performed on three positive controls, five treated masks and one negative control.
Results. The five decontaminations showed significant (P<0.05) but different degrees of reductions of S. aureus and P. aer- uginosa. VHP, dry heat treatment and ethanol treatment adequately reduced the initial contamination. The 4 min UV treatment allowed only a reduction to five orders of magnitude for face mask respirators. The methylene blue treatment induced a reduc- tion to two orders of magnitude.
Conclusions. The three methods that showed a log10 reduction factor of 6 were the dry heat method, VHP and ethanol bath treatment. These methods are effective and their establishment in the medical field are easy but require economic investment.