Process of growing microbes in a new environment under defined conditions sequentially over time.

Serial passage studies are used to study the evolution of drug-resistance or virulence. For instance, growing bacteria on plates containing an antibiotic and then culturing the colonies that grow on to fresh plates with a higher concentration of drug and repeating until no growth can be obtained. The resistant colonies are compared to initial colonies to understand how the resistance is developed. This experiment determines the highest achievable level of drug-resistance and how fast this can occur.