The generation and dispersal of infectious respiratory particles - using respiratory and oral commensal bacteria as index organisms for respiratory pathogens

Abstract

There is a need to better understand the dispersal and spread of respiratory pathogens. However, carrying out controlled microbiology-based simulation studies is difficult particularly if the target organism is highly pathogenic or is currently unknown. An alternative approach is to use commensal respiratory bacteria as index organisms. Two cohorts of healthy volunteers were asked to perform defined respiratory activities within a purpose-built flexible-film isolator. The dispersal of bacteria-laden particles was assessed via passive and active air sampling. Activities were carried out with or without a face covering. Dispersal of respiratory particles differed with individual. During speech, increased vocal volume was associated with a significant increase in the number of respiratory bacteria deposited on surfaces and recovered from the air. Disposable (IIR) medical face masks significantly reduced droplet deposition and reduced the odds of detecting higher numbers of airborne bacteria by 87% (CI: 63%, 96%). Transparent face coverings were as effective as (IIR) face masks, but face shields had limited efficacy, particularly when worn by individuals who dispersed high numbers of respiratory particles. Index organisms can be used to study respiratory transmission in the absence of the target pathogen. This study demonstrates their utility in the context of pandemic preparedness.