Rapid Phenotypic Antimicrobial Susceptibility Testing: From Proof of Concept to Product

Antimicrobial susceptibility testing (AST) is a routine hospital test that currently takes 8-24 hrs plus a 1-5 day sample preparation step to deliver results, leading to the use of broad spectrum antibiotics and the consequent formation of antibiotic resistant bacteria. Our previous work introduced a rapid and accurate AST system on a chip capable of delivering results in under 6 hours thus providing same day AST results (Avesar et al., 2017). The method makes use of a sensitive fluorescent marker and individual stationary-nanoliter droplet arrays (SNDA), a novel microfluidic device which robustly creates hundreds of single-cell culture environments within dozens of wells embedded in the SNDA. The perfused wells are monitored every 30 minutes to detect bacterial growth by tracking the fluorescence of the cell medium in the wells, the kinetic fluorescence profile of each well is fit to either a linear or exponential model. Slopes calculated from the fits of different antibiotic treatments are compared to make determinations whether bacteria from an infection site is resistant or susceptible to the tested antibiotic.

Despite its novelty, this proof of concept, however, serves only for research purposes. In this work, we demonstrate the first steps of the R&D plan suggested by Nanosynex to take this proof of concept from the lab to the market. For that purpose we further develop a microfluidic cartridge with 2 goals in mind: (i) Develop a multiplexed card, constitutes many SNDAs in parallel for simultaneous testing of multiple antibiotic treatments and (ii) Design an SNDA geometry which is compatible with mass production techniques, to spare time and cost of manufacturing.

Overall, our efforts are aimed for the ultimate goal of upgrading our SNDA from a proof of concept stage to a commercialized product.