Is there a TB “superspreader” phenotype? Learn more from UW's Drs. Horne and Hawn...

Drs. David Horne, SEATRAC member and associate professor of medicine, and Tom Hawn, SEATRAC Development Core co-director and professor of medicine discuss the possibility of "superspreader" phenotypes in their latest publication.

Infectiousness is determined, in part, by a person’s ability to generate small particles that float in the air (aerosolized) and may contain mycobacterium.

It is likely that a minority of persons with TB cause the majority of transmission and new infections.

Unfortunately, we currently lack clinical tools to identify who the most infectious persons are as commonly used tests such as chest X-ray appearance or sputum smear grade poorly correlate with infectiousness. Cough aerosol sampling system (CASS), a research tool to collect aerosol samples from persons with TB is the best validated test for determining a person’s infectiousness. Investigators from the University of Washington and the Kenya Medical Research Institute enrolled persons with TB in Nairobi into a study to estimate their infectiousness using CASS, identify factors associated with producing infectious aerosols, and investigate whether unique gene signatures are associated with producing infectious aerosols. They found that younger age, preserved muscle mass, higher bacillary burden and systemic inflammation (high C-reactive protein levels) are associated with producing infectious aerosols, as was a low TNF level. Using whole blood transcriptomics with gene set enrichment analyses, they identified 8 gene sets that are associated with producing infectious particles independent of a person’s bacillary burden. 

Next steps are to investigate the pathways that determine a person’s infectiousness and identifying clinical tools that could detect highly infectious persons.

Read the full article: Mycobacterium tuberculosis cough aerosol culture status associates with host characteristics and inflammatory profiles | Nature Communications