Resazurin reduction based colorimetric antibiogram in microfluidic plastic chip

When drug-resistant bacteria pose a threat, a simple and inexpensive method for identifying their presence and quickly determining the right antibiotic for treatment, is critical. A simple optical detection technique combined with microfluidic technology will have great potential for configuring a portable antibiogram device. We report a colorimetric antibiogram method, based on viability-dependent resazurin dye reduction (intense blue colour changing to pink and leuco). The antibiogram protocol was developed initially in a 96-well plate format. This was tested using 20 clinical bacterial isolates against the minimum inhibitory concentration (MIC) of four antibiotics after 6h of incubation. The antibiogram results obtained colorimetrically or visually were matched and confirmed with those of the liquid turbidity method (LTM). This antibiogram protocol was then transferred to a Poly(methyl methacrylate) (PMMA) plastic microfluidic chip containing 40 micro wells (8 rows and 5 columns, 20μl volume per well). These microfluidic units can serve as disposable devices for portable instrumentation. The plastic microfluidic chip antibiogram showed 98% match with what was obtained in the 96-well plate method. The microfluidic chip offers a novel, compact and inexpensive platform technology for testing/screening of drug-resistant bacteria, and determining their antibiogram. This approach will lead the way for developing portable and low-cost point-of-care antibiotic susceptibility testing instrumentation for the future.