EVAPORATION OF BACTERIA-LADEN SURROGATE RESPIRATORY FLUID DROPLETS: SESSILE MODE V/S LEVITATED MODE*

The mayhem caused by Covid-19 proves that intensive research is necessary to decode the infection pathways of respiratory ailments involving both bacteria and viruses as pathogens. Transmission of infectious bacteria or viruses occurs via four major modes, namely direct contact, indirect contact (fomites), large droplets, or fine aerosols. A droplet is an integral part of aerosol spray and exhalations from the host. Therefore, it is a holistic study to understand the desiccation dynamics of infected droplets coupled with the infection study of the crystal/settled droplet. Given the complexity of the experiment with actual bacteria/viruses in respiratory fluid, such studies have rarely been attempted. In our study, we have experimentally compared the contact-free environment precipitates (via the levitated mode of evaporation) and the precipitates on hydrophilic substrates (via the sessile mode of evaporation), maintaining the same initial volume of the bacterial solution, aiming to deduce the effect of evaporation on bacterial survival and its virulence. The study examines mass transport, the deposition pattern of bacteria in the precipitates, and their survival and virulence. The desiccation dynamics play a pivotal role in bacterial survival and virulence. The evaporation mode influences the bacteria's viability within the droplet, with the sessile precipitate harboring more non-viable, aged, and dead bacteria than the levitated case.