The lowest concentration of an antimicrobial agent that prevents growth of more than 99% of a microorganism in a solid medium or broth dilution susceptibility test. Typically, when MICs tested in a standardized method are aggregated for one species, a single Gaussian-shaped MIC distribution is observed, which corresponds to the phenotypically wild-type (WT) distribution of that species (i.e., the distribution of organisms that lack phenotypically detectable resistance mechanisms). Additional distributions with higher overall MICs may be identified that correspond to intrinsically or naturally resistant organisms (i.e., phenotypically non-wild type distribution).