broth dilution method Macro Broth Dilution Method A method to determine the minimum inhibitory concentration (MIC) of antibiotics in which growth media is pipetted into a test tube. Each tube contains a known concentration of drug and is inoculated with a known quantity of bacteria. The tubes are incubated for a specified period of time and each is assessed for bacterial cell growth. The drug concentration in the first tube showing no growth is known as the MIC for that antibiotic. MACRO BROTH DILUTION Macro Broth Dilution Method