Enumeration of Ampicillin-Resistant $E.\ Coli$ in Blood Using Droplet Microfluidics and High-Speed Image Processing

Bacteria entering the bloodstream causes bloodstream infection (BSI). Without proper treatment, BSI can lead to sepsis which is a life-threatening condition. Detection of bacteria in blood at the early stages of BSI can effectively prevent the development of sepsis. Using microfluidic droplets for single bacterium encapsulation provides single-digit bacterial detection sensitivity. In this study, samples of ampicillin-resistant E. coli in human blood were partitioned into millions of
$30\ \mu \mathrm{m}$
diameter microfluidic droplets and followed by 8-hour culturing. Thousands of fluorescent bacteria from a single colony filled up the positive droplets after the culturing process. A circle detection software based on Hough Transform was developed to count the number of positive droplets from fluorescence images. The period to process one image can be as short as 0.5 ms when the original image is pre-processed and binarized by the developed software.