Quantification of airborne respiratory microflora provides insights into airborne infection risk

OBJECTIVES: 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.