Development of a Test System To Apply Virus-Containing Particles to Filtering Facepiece Respirators for the Evaluation of Decontamination Procedures

Abstract

A chamber to apply aerosolized virus-containing particles to air-permeable substrates (coupons) was constructed and validated as part of a method to assess the virucidal efficacy of decontamination procedures for filtering facepiece respirators. Coliphage MS2 was used as a surrogate for pathogenic viruses for confirmation of the efficacy of the bioaerosol respirator test system. The distribution of virus applied onto and within the coupons was characterized, and the repeatability of applying a targeted virus load was examined. The average viable virus loaded onto 90 coupons over the course of 5 days was found to be 5.09 ؎ 0.19 log 10 PFU/coupon (relative standard deviation, 4%). To determine the ability to differentiate the effectiveness of disinfecting procedures with different levels of performance, sodium hypochlorite and steam treatments were tested in experiments by varying the dose and time, respectively. The role of protective factors was assessed by aerosolizing the virus with various concentrations of the aerosol-generating medium. A sodium hypochlorite (bleach) concentration of 0.6% and steam treatments of 45 s and longer resulted in log reductions (>4 logs) which reached the detection limits for both levels of protective factors. Organic matter (ATCC medium 271) as a protective factor afforded some protection to the virus in the sodium hypochlorite experiments but was not a factor in the steam experiments. The evaluation of the bioaerosol respirator test system demonstrated a repeatable method for applying a targeted viral load onto respirator coupons and provided insight into the properties of aerosols that are of importance to the development of disinfection assays for air-permeable materials.

Comparison of spike and aerosol challenge tests for the recovery of viable influenza virus from non‐woven fabrics

“…The different amplitude and frequency of the agitation method may cause different relative acceleration motion between eluent and non‐woven fabrics, yielding different recovery results. Nevertheless, Fisher et al 19 found that sonication, vortexing, and shaking exhibited similar efficiency and repeatability for extracting aerosolized virus from respirator coupons, suggesting agitation methods gave minimal difference in virus recovery efficiency. Second, volume of the eluent and area of the non‐woven fabric used in aerosol challenge tests were larger than spike tests (e.g., 49 cm 2 versus 1 cm 2 and 5 ml versus 1 ml), leading to different volume to area ratios in the two tests (~0·1 ml/cm 2 versus 1·0 ml/cm 2 ).…”

“…All three non‐wovens were made by a spunbond process with basis weight from 33·9 to 46 g/m 2 . Spunbond non‐woven fabrics in this basis weight range are typically used as the outer layer of respirators where a significant amount of aerosolized virus can deposit 19. Both hydrophobic (PP and PET) and hydrophilic surfaces (Nylon) were included in this study.…”

Survival of Bacteriophage MS2 on Filtering Facepiece Respirator Coupons

“…The media, virus, and host cells, used in this research, have been described previously (Fisher et al, 2009). American Type Culture Collection (ATCC) medium 271 (www.atcc.org), a modified LB medium amended with glucose, was used to grow the host bacterium Escherichia coli (ATCC 15597) and prepare, store, recover, aerosolize, and assay MS2 (ATCC 15597-B1).…”

“…Therefore, infectious microorganisms must be inactivated or removed from the surfaces of FFRs for reuse to be practical. Researchers have investigated the feasibility of the removal and/or inactivation of microorganisms on FFRs (Fisher et al, 2009;Salter et al, 2009;Viscusi et al, 2009a;Viscusi et al, 2009b;Viscusi, King, & Shaffer, 2007;). However, the need for FFR decontamination is not well characterized as there are limited data on the survival of microorganisms on FFRs over a prolonged period of time (Brosseau, McCullough, & Vesley, 1997;Reponen et al, 1999;Wang et al, 1999).…”

“…Data for viruses in particular are lacking. Previously, Rengasamy, Fisher, & Shaffer (2009) showed that greater than 10% of the challenge bacteriophage MS2 survived for 20 hours at 22ºC and 30% relative humidity (RH) on FFR coupons, including those with antimicrobial additives. The aim of this study was to determine the long-term survivability of a virus (MS2) inside and on the surface of FFRs under hospital-simulated temperature and humidity conditions.…”