Self-Assembly and Morpho-Topological Changes of Klebsiella Pneumoniae in drying droplets

Biofluid droplets ejected from infected humans and animals are a significant source of disease transmission.. The fate of pathogens in these droplets depend on their resistance to the Physico-chemical changes in their environment(droplet). While many pathogens die during the phase change process, some survive these conditions. The study focus on bacteria-laden droplets, drying on a glass substrate. Klebsiella pneumoniae, an opportunistic bacterium that commonly infects humans, is suspended in Milli-Q water and surrogate respiratory fluid and the droplets are allowed to dry in a controlled environment. Micro-PIV quantifies the flow inside the droplet, while microscopy interferometry technique is used to analyze the thin film instability. Confocal microscopies reveal the bacterial self-assembly mechanism. SEM and AFM reveal the morpho-topological variations in bacterial deposits. An order to disorder transition in bacterial packing is seen at the edge deposits. The packing density variation correlates well with the viability and infectivity variations of the deposited bacteria. The insights obtained from this study will help understand disease transfer through droplets, e.g., through open wounds.