ABSTRACT
MEASUREMENTS OF ANTIMICROBIAL ACTIVITY Minimum Inhibitory and Minimum Bactericidal Concentrations The minimum inhibitory concentration and minimum bactericidal concentration (MIC and MBC) have been the major parameters used to measure the in vitro activity of antimicrobials against various pathogens. Although MIC and MBC are excellent predictors of the potency of an antimicrobial against the infecting organism, they provide essentially no information on the time course of antimicrobial activity. For example, the MBC provides minimal information on the rate of bactericidal and fungicidal activity and on whether killing can be increased by higher drug concentrations. In addition, MIC provides no information on growth inhibitory effects that may persist after antimicrobial exposure. These persistent effects are due to three different phenomena: the postantibiotic effect (PAE), the postantibiotic sub-MIC effect (PAE-SME), and the postantibiotic leukocyte enhancement (PALE) (6-8). The killing effects of increasing concentrations on the bactericidal and fungicidal activity of antimicrobials combined with the magnitude of persistent effects give a much better description of the time course of antimicrobial activity than that provided by MIC and MBC.
