Quantification of airborne respiratory microflora provides insights into airborne infection risk

Abstract

Objectives To develop airborne respiratory microflora quantification as a method of quantifying airborne infection risk that is more readily applicable than airborne pathogen sampling, without being subject to the limitations and caveats of CO2 monitoring. Methods Digital polymerase chain reaction targeting a mixture of Streptococcus and Haemophilus genera common to the respiratory tract was first tested under laboratory conditions and then tested on aerosol sampled from around a hospital in Sydney, with polymerase chain reaction quantification of SARS-CoV-2 genome copies also being carried out on the samples. Results Clear signals were obtained from every location within the hospital, with a significantly higher signal being observed in more densely crowded, less well-ventilated areas. When SARS-CoV-2 was present within the aerosol samples, the respiratory microflora signal correlated with the number of SARS-CoV-2 copies. Conclusions Airborne respiratory microflora can be used as a marker for airborne infection risk. Using the value in conjunction with pathogen sampling provides in-depth insights into the relative infection risk of a space, and a clear marker which can be used to compare between different pathogen sampling studies.