Evaluation of bioaerosol samplers for the detection and quantification of influenza virus from artificial aerosols and influenza virus–infected ferrets

Abstract

Background: Bioaerosol sampling devices are necessary for the characterization of infectious bioaerosols emitted by naturally-infected hosts with acute respiratory virus infections. Assessment of these devices under multiple experimental conditions will provide insight for device use. Objectives:The primary objective of this study was to assess and compare bioaerosol sampling devices using a) an in vitro, environmentally-controlled artificial bioaerosol system at a range of different RH conditions and b) an in vivo bioaerosol system of influenza virus-infected ferrets under controlled environmental conditions. Secondarily, we also sought to examine the impact of NSAIDs on bioaerosol emission in influenza virus-infected ferrets to address its potential as a determinant of bioaerosol emission. Methods:We examined the performance of low and moderate volume bioaerosol samplers for the collection of viral RNA and infectious influenza virus in vitro and in vivo using artificial bioaerosols and the ferret model of influenza virus infection. The following samplers were tested: the polytetrafluoroethylene filter (PTFE filter), the 2stage National Institute of Occupational Safety and Health cyclone sampler (NIOSH cyclone sampler) and the 6-stage viable Andersen impactor (Andersen impactor). Results:The PTFE filter and NIOSH cyclone sampler collected similar amounts of viral RNA and infectious virus from artificially-generated aerosols under a range of relative humidities (RH). Using the ferret model, the PTFE filter, NIOSH cyclone sampler and the Andersen impactor collected up to 3.66 log 10 copies of RNA/L air, 3.84 log 10 copies of RNA/L air and 6.09 log 10 copies of RNA/L air respectively at peak recovery. Infectious virus was recovered from the PTFE filter and NIOSH cyclone samplers on the peak day of viral RNA recovery. Conclusion: The PTFE filter and NIOSH cyclone sampler are useful for influenza virus RNA and infectious virus collection and may be considered for clinical and environmental settings. K E Y W O R D S bioaerosol samplers, bioaerosols, ferret model, influenza virus | 565 BEKKING Et al.

Comparison of three air samplers for the collection of four nebulized respiratory viruses

“…As an alternative to agar, liquid medium is also frequently used in the cascade impactor, since the chances of virus desiccation are smaller and sample processing after collection is not needed 15,[40][41][42] . However, the high flow velocities within the sampler push aside liquid medium where the air stream hits the surface, creating a dent, thereby increasing the jet-to-plate distance.…”

Recent advancements in the measurement of pathogenic airborne viruses

“…Viral infectivity can be expressed by the ratio of viral copies to PFUs, which can vary significantly depending on the type of virus, air sampler, environmental stress and culture conditions ( Yang et al, 2011 ). For influenza viruses (H1N1 and H3N2) collected with air samplers, the ratios of 7.5×10 3 –1.0×10 4 copies/PFU were reported and were higher for those collected in the nebulizer, that is before aerosolization, suggesting infectivity loss during aerosolization and sampling in addition to environmental stress ( Bekking et al, 2019 ), which needs to be considered when assessing the effects of environmental stress on the stability of airborne viruses.…”

“…The first and second stages of the sampler collected non-respirable particles larger than 4 μm and those between 1 and 4 μm, respectively; the PTFE filter in the third stage collected particles smaller than 1 μm, and the collected particles were eluted thereafter. The NIOSH cyclone (NIOSH-251) was used to collect airborne murine norovirus (MNV) and influenza viruses at 3.5 LPM ( Bekking et al, 2019 , Boles et al, 2020 ). It collected a significantly lower RNA concentration of the MNV than the SKC BioSampler; however, there were no significant differences in the relative concentrations of MNVs with intact capsids between the two samplers ( Boles et al, 2020 ).…”

“…It collected a significantly lower RNA concentration of the MNV than the SKC BioSampler; however, there were no significant differences in the relative concentrations of MNVs with intact capsids between the two samplers ( Boles et al, 2020 ). Infectivity losses of influenza viruses were also observed during aerosolization and sampling ( Bekking et al, 2019 ).…”

“…The choice of the measurement method depends strongly on the extent to which the viruses are damaged. In fact, environmental stress such as ambient temperature and humidity, ROS, and UV light, as well as aerosol generation and sampling can cause physical and biological damage to certain parts of the viruses, e.g., nucleic acids and surface/inner proteins, resulting in loss of viability ( Christopher and ‡ GwangPyo, 2007 , Bekking et al, 2019 , Sagripanti and Lytle, 2020 ).…”