Use of Common Disinfectants to Remove Influenza Virus from Elastomeric Respirators

Background: While it has been shown that common hospital surface disinfectants are effective against influenza virus, there has been no data published on their effectiveness to remove influenza from the surface of reusable elastomeric respirators. As the use of reusable respirators may be necessary during shortages of disposable respirators, knowledge of effective disinfection techniques is important. Objective: To determine the effectiveness of disinfectants to eradicate influenza from the surface of elastomeric respirators. Methods: 2009 H1N1 influenza virus was titered to a concentration of 100 pfu/50 µL. A 1 cm2 smooth section of a sterilized respirator (3M model 7500) was inoculated with 50 µL of the titered influenza virus and allowed to air dry for 5 minutes. The respirator surface was then disinfected with one of 3 disinfectants contained in a pre-moistened wipe (0.28% 2-2-p-diisobutyl phenoxy ethoxy ethyl dimethyl ammonium chloride plus 17.2% isopropyl alcohol [Caviwipe, Metrex Research Corporation], 1:10 bleach dilution plus detergent [Dispatch, Caltech Industries] or 70% isopropyl alcohol [Webcol, Kendall]) using a standardized protocol. A fourth group received no disinfectant wipe and served as a positive control. All tests were performed in triplicate and each group included negative controls. A sterile swab pre-moistened with viral transport media was used to swab the inoculated surface using a standardized protocol. Fifty µl of the sample was cultured using R-Mix cells and standard methods. Nucleic acids were extracted from the remaining sample and were tested for influenza using RT-PCR (GenProbe Proflu+, Prodesse). Cultures and PCR assays were performed in duplicate for each specimen. Results: A total 20 respirators were tested. Positive controls showed recovery of 35 to 73 pfu of influenza and PCR was positive at 27 to 28 PCR cycles. Influenza virus could not be recovered from any respirator treated with either a quaternary ammonium/isopropyl alcohol or bleach-detergent impregnated wipe but 1 of 3 and 2 of 3 were positive by PCR, respectively. However, Influenza virus was recovered from 2 of 3 respirators treated with 70% isopropyl alcohol by culture (range 17 to 37 pfu) and all 3 were positive by PCR. Conclusions: Quaternary ammonium/isopropyl alcohol and bleach-detergent pre-moistened wipes were found to effectively eradicate influenza from the surface of elastomeric respirator material while 70% isopropyl alcohol alone was not shown effective. PCR testing was not shown to be an accurate surrogate marker for viable influenza. Further study is needed to identify effective methods for field disinfection of the more complicated surfaces of elastomeric respirators.