The ability of Mycobacterium tuberculosis (MTB), a serious respiratory infection, to form snake-like cords was first noted nearly 80 years ago. In a study published October 20 in the journal Cell, investigators report the biophysical mechanisms by which these cords form and demonstrate how several generations of dividing bacteria hang together to create these structures that enable resistance to antibiotics.
The study used a unique combination of technologies to address the role of MTB cord formation. One was a lung-on-chip model, which allowed the researchers to get a direct look at “first contact” between MTB and host cells at the air-liquid interface in the lungs. This revealed that cord formation is prominent in early infection. The researchers also used a mouse model that develops pathologies mimicking human tuberculosis, allowing them to obtain tissue that could be studied using confocal imaging and confirming that cording also occurs early in infection in vivo.
The work yielded several new findings about how these cords interact with and compress the cell nucleus, how this compression affects the immune system and connections between host cells and epithelial cells, and how cord formation affects the alveoli in the lungs. The study also revealed how these cords retain their structural integrity and how they increase tolerance to antibiotic therapy.
Future research will focus on understanding whether cord formation enables new functionality to known effectors of MTB pathogenesis, many of which are located on the MTB cell wall. In addition, it will look at the consequence of tight-packing on the bacteria within the clump and how this may lead to a protective effect against antibiotics.