Responses of bacteria in aerosol: Informing transmission of a deadly foe, tuberculosis

Tuberculosis (TB) is the single greatest cause of death from any bacterial disease. TB is transmitted between people via aerosol droplets generated when infected individuals cough. More than one-quarter of the world’s population harbour the agent of TB, Mycobacterium tuberculosis (Mtb), in their lungs, testament to the bacteria’s transmission success. Surprisingly, we know very little about the biological properties of Mtb that promote this. Understanding the state of Mtb as it enters aerosols and how it behaves and responds to changing conditions (e.g. temperature and droplet desiccation) following release by coughing, will identify new opportunities to control TB. We have sampled Mtb aerosols expelled by TB patients and examined the state of the bacteria by measuring their gene expression. Preliminary results indicate that the bacteria are distinctive with properties not recognised in previous lab studies. In order to investigate how these properties may change in response to the environment on entry into, and residence within in aerosol droplets, we first undertook laboratory studies to determine how well Mtb survive. Previously reported studies[1,2] present very different timescales for Mtb aerosol survival. We maintained the bacterial aerosol in a Goldberg Drum and found that both the lab strain, H37Rv, and related vaccine strain, BCG, survived well with a decline of 50% after 2 hours. We sampled H37Rv to measure changes in gene expression before entry into, and within aerosol for up to 2h. We identify distinct gene expression profiles, with evidence that Mtb responds to both the nebulisation process and aerosol residence.

Join today to view and download the full abstract/presentation