Gravity-driven microfluidic assay for digital enumeration of bacteria and for antibiotic susceptibility testing

Abstract

Easy-to-use gravity-driven step emulsification devices are capable of digital enumeration of bacteria and antibiotic susceptibility testing within 5 hours.

Microfluidic formation of crystal-like structures

“…They demonstrated formation of uniform 2D droplet crystals, each having individual droplets with different diameter and narrow standard deviation. Before concluding this section, we want to highlight a recent work by Kao et al 65 where the microfluidic crystal was formed without the support of any type of external flow equipment, nor syringe pump, nor centrifugal force. The device was still based on the step emulsification process where the continuous phase was, as usual, added in the droplet generation chamber; moreover, the dispersed phase as well was added to a reservoir in the microfluidic device using a pipette.…”

The Role of Single-Cell Technology in the Study and Control of Infectious Diseases

“…Phenotypic AST, which involves the culture of the pathogen in the presence or absence of antibiotics, may help guide treatment options, but existing conventional assays have low sensitivity and require a long time of 12–48 h for cell regrowth to achieve measureable assay outcomes [ 114 , 115 ]. Higher-sensitivity single-cell digital assays that have been recently reported can obtain measurable signals without requiring cell regrowth and could be the answer to reducing AST turnaround times ( Figure 3 B) [ 116 , 117 , 118 ]. Another application of digital assays could be in quantifying viral reservoirs in patients at a single-cell resolution.…”

“…Image reproduced from reference [ 102 ] under a Creative Commons License. ( B ) Pump-free droplet emulsion generation system that is capable of performing antimicrobial-susceptibility testing (AST) of different species of bacteria with a turnaround time of ≈5 h. Image reproduced with permission from reference [ 117 ]. Copyright 2020 Royal Society of Chemistry.…”

Challenges in Microfluidic and Point-of-Care Phenotypic Antimicrobial Resistance Tests

“…Resazurin dye reduction is commonly used to detect metabolism changing from blue to a pink color and from non-fluorescent to a strong red fluorescence in the presence of metabolically active bacteria. Resazurin has been incorporated in a number of AMR microfluidic devices as well as traditional broth microdilution methods (Boedicker et al, 2008;Elavarasan et al, 2013;Elshikh et al, 2016;Hsieh et al, 2018;Kao et al, 2020). However, the fluorescence of resorufin (the product of resazurin) is suspectable to changes in pH.…”