Improving droplet microfluidic systems for studying single bacteria growth.

Antimicrobial resistance remains a global threat with ~ 5 million deaths in 2019 alone and 10 million deaths projected every year by 2050. Current tools employed in the analysis of bacteria can be time inefficient, leading to delayed diagnosis and treatment. In this work, we develop a microfluidic setup capable of bacteria incubation and detection of growth in ~ 2 h. We fabricated polydimethylsiloxane (PDMS) microchips via soft lithography, enclosed microchannels by plasma bonding to glass, and utilized PDMS blocks for simplified connection of devices to a flow system. We generated uniform droplets enclosing zero, one or two bacteria within our devices, and incubated droplet-encapsulated bacteria with 100 × lower concentrations of a fluorescence probe of bacterial growth compared to prior work. We assessed bacterial growth via laser induced fluorescence after room temperature incubation for 2 h and obtained a range of signals corresponding to droplets with or without bacteria. Our devices allow for online droplet incubation, monitoring, detection, and tracking. Developing microfluidic chips for single bacteria studies will improve the analysis and treatment of antimicrobial resistance.