Currently, pathogenic microorganisms are characterized for antimicrobial susceptibility on “post culture positive” samples via growth in multiple wells with varying concentrations of different antimicrobials.  This approach is very well established, and measures the “functional antimicrobial susceptibility” (the gold standard, according to clinicians) but is also very slow.
Some emerging techniques use rapid PCR type methods to characterize the “structural antimicrobial susceptibility” (or, the presence of a specific marker that might indicate resistance).  This approach is somewhat faster, but also very problematic (the approach does not cover all known markers, not all resistance mechanisms have a known marker, and new mechanisms are constantly emerging).
Other approaches speed up the process on a “post blood culture positive” sample by using accelerated methods (such as advanced imaging) to characterize bacteria growth.  These are all incremental improvements.

Our Approach

In our InSpector-01 tool, we characterize the metabolic activity of the causative pathogen.  We can do the same measurement with a varying amount of antimicrobial.  The result is a rapid characterization of both MIC (Minimum Inhibitory Concentration MIC) and MBC (Minimum Bactericidal Concentration) of the candidate antimicrobial.

For this, we do need a small period of incubation (about 4 hours) from the blood draw.  The initial blood draw has about 1-10 copies of the bacteria.  We need to incubate this in a rich media until we have about 500 copies of the bacteria (this will take 3-4 hours).  At that point, we aliquot the sample into multiple parts, add the desired antimicrobial, wait for 20 minutes, and test (we can use the same reagent and hardware as in InSpector-01).

The output from our test scales with the antimicrobial concentration (illustrated in the chart below for Vancomycin against S. aureus).  The turn around time for our test (from the blood draw) is about 5 hours.  This is a radical improvement over currently used methods, and also those under development.

Current Status

This tool is now ready for clinical testing.  We anticipate that clinical testing will also entail some changes to the hardware/reagent/software, and that it will be ready for discussion with the FDA in 2020.