Rapid antimicrobial susceptibility tests on an integrated microfluidic device for precision medicine of antibiotics

This study reports an integrated microfluidic device that was capable of executing rapid antimicrobial susceptibility tests with one, two, or even three antibiotics against two clinically isolated multi-drug-resistant bacteria strains (including carbapenem-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus). Bacteria were automatically mixed for 10 min with serially diluted antibiotics with a novel, membrane-type micromixer consisting of two circular micropumps, and the minimum inhibitory concentrations (MIC) were then determined via simple colorimetric reactions in only 4.5-6 h using only 3 μL of bacteria sample of each reaction (as opposed to 24 h and 50 μL, respectively, with the conventional broth micro-dilution method). In addition to determining MICs of antibiotics (ceftazidime, gentamicin, meropenem, vancomycin and linezolid), interaction effects across antibiotics combinations (gentamicin/meropenem or ceftazidime/gentamicin/meropenem) at different dosages were explored. The efficacy of polypharmacy showed additivity when gentamicin or ceftazidime/gentamicin were combined with meropenem to treat carbapenem-resistant Escherichia coli. This represents the first time that the perplexing clinical decision to choose multiple antibiotics for combination therapy against drug resistant bacteria can be realized on an integrated microfluidic device within 6 h.