See also bacterial fitness.

Physiological cost suffered by bacteria to acquire drug resistance ability or fitness.

Many antibiotic resistance mechanisms are associated with a fitness cost that is typically observed as a reduced bacterial growth rate. The magnitude of the fitness cost is the main biological parameter that influences the rate of development of resistance, the stability of the drug-resistant microbe and the prevalence at which a drug-resistant microbial population might decrease if antibiotic use were reduced. Resistance mutations may be expected to impart a fitness cost because they target important biological functions in the cell. However, in most cases, compensatory mutations lessen or alleviate any fitness costs associated with drug-resistance.