Can bacteria develop resistance to disinfectant over several generations? The Kirby-Bauer disk method measures how well an antimicrobial agent stops bacteria from growing. A larger clear zone around the disk means stronger killing power. You grow E. coli on agar plates with filter paper disks soaked in 25%, 50%, and 75% Dettol disinfectant. After two days, you measure the inhibition zone (the bacteria-free ring around each disk). Then you collect surviving bacteria from the edge and use them to start the next generation. You repeat this for four generations. Higher concentrations produce larger inhibition zones. However, zone sizes stay stable across all four generations, showing no sign of increasing resistance.