Assessing Activity of Antimicrobial Agents and Screening Antibiotic-Resistant Bacteria Through DREAM Assay

Antibiotics have assumed importance in the scene of medicine due to their activity against bacterial infections. During the course of evolution, bacteria have been developing routes to overcome damaging effects of antibiotics. Antibiotic resistance is an intriguing development that has taken the world of anti-microbial therapy by storm. Among the methods described in literature for assessing anti-microbial activity, those using metabolic activity as a measure of bacterial viability provide estimates closer to the actual. The dye reduction-based electron-transfer activity monitoring assay (DREAM assay) utilizes the redox dye methylene blue as an indicator of microbial activity. The DREAM assay coefficient is presented herein as a measure of the extent of microbial reduction of methylene blue to a colorless form under experimental conditions. This novel metric was successfully employed to evaluate activity of three common antibiotics—ampicillin, gentamicin, and ciprofloxacin—and leaf extracts of Azadirachta indica and Ocimum sanctum. Results corroborated significantly with the conventional disk diffusion method commonly used for anti-microbial testing. The principle of microbial electron transfer was then successfully extended to assess antibiotic susceptibility of known resistant and sensitive strains of Escherichia coli. This method possesses the advantage of detecting anti-microbial activity in a simple, cost-effective, and rapid manner.