Lecture Link: Antibiotics and resistance: The mutant factor
WHAT IS MPC?
MPC is a novel measurement meant to determine the drug concentration that blocks 100% of the growth of mutant bacterial cells in high-density populations. This measurement allows assessment of the "likelihood for antimicrobial agents to select for antimicrobial resistance at clinically relevant drug concentrations," said Dr. Blondeau. Clinically relevant drug concentrations are the serum concentrations we are trying to achieve to eliminate the infection. A drug with a high MPC is likely to cause resistance.Mutations confer resistance, and these mutations may not be detected at the bacterial concentrations typically used for culture and sensitivity testing. According to Dr. Blondeau, these mutations occur at much higher bacterial concentrations, which are more representative of the true bacterial burden. If MPC data are used for dosing, rather than the minimum inhibitory concentration (MIC) data currently used, there may be a better chance of eradicating disease and less risk of inducing resistance.
Thus, the data we currently use for antibiotic selection are not as effective as decreasing the risk of inducing resistance. MPC data may ultimately replace MIC data and allow for more effective antibiotic therapy.
Dr. Blondeau also noted some things practitioners can do to help stem the rise in antimicrobial resistance:
1. Blondeau JM. Antibiotics and antimicrobial resistance. Presented at the Annual Meeting of the American College of Veterinary Internal Medicine; June 2012.