Mutation prevention concentration of ceftriaxone, meropenem, imipenem, and ertapenem against three strains of Streptococcus pneumoniae

This investigation tested the mutation prevention concentration (MPC) concept using imipenem, meropenem, ceftriaxone, and ertapenem against three strains of Streptococcus pneumoniae (PCN MIC = 0.012, 1, 8 mg/L, respectively). MIC, MBC, and MPC values for each of the β-lactams did not differ by more than one tube dilution. While an interesting concept, MPC may not apply to antimicrobials that do not utilize a dual targeting system, such as β-lactams, or to bacteria that exhibit multiple mechanisms of resistance and/or mutate at a rate where the frequency would likely be captured by the standard inoculum size used in routine MIC testing.