Abstract
Since the discovery of antibiotics, the emergence of antibiotic resistance has become a global issue that is threatening society. In the era of antibiotic resistance, finding the proper antibiotics through antibiotic susceptibility testing (AST) is crucial in clinical settings. However, the current clinical process of AST based on the broth microdilution test has limitations on scalability to expand the number of antibiotics that are tested with various concentrations. Here, we used color-coded droplets to expand the multiplexing of AST regarding the kind and concentration of antibiotics. Color type and density differentiate the kind of antibiotics and concentration, respectively. Microscopic images of a large view field contain numbers of droplets with different testing conditions. Image processing analysis detects each droplet, decodes color codes, and measures the bacterial growth in the droplet. Testing E. coli ATCC 25922 with ampicillin, gentamicin, and tetracycline shows that the system can provide a robust and scalable platform for multiplexed AST. Furthermore, the system can be applied to various drug testing systems, which require several different testing conditions.
Highlights
Antibiotic resistance is an emerging issue in global healthcare [1,2]
Bacterial samples mixed with antibiotics, color dye, and oil with a surfactant flow into a junction in a cross-shaped microfluidic color dye, and oil with a surfactant flow into a junction in a cross-shaped microfluidic channel that generates color-coded droplets (Figure 2A)
A sample test of E. coli with three clinically important antibiotics and three concentrations validated the system’s feasibility
Summary
Misuse and overuse of antibiotics are the primary factors that are increasing the development of antibiotic-resistant bacteria [3]. In the clinical environment, determining the antibiotic resistance of bacteria from infected patients, through a process referred to as the antibiotic susceptibility test (AST), is an urgent need to save patients. The micro-well plate is incubated at 37 ◦ C for 16–20 h, and the optical density of the testing well is measured to determine bacterial growth. Based on the minimal inhibitory concentration (MIC), antibiotic resistance is determined and the antibiotics needed are prescribed to the infected patient. This gold standard method is considered accurate and applicable in clinical settings. Immobilization in hydrogel, electrophoresis, and trapping narrow microfluidic channels captures bacterial cells in a small view field that is required for single-cell imaging in high magnification [10,11,12]
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