The minimum bactericidal concentration (MBC) is the lowest concentration of an antibacterial agent required to kill a particular bacterium. It can be determined from broth dilution minimum inhibitory concentration (MIC) tests by subculturing to agar plates that do not contain the test agent. The MBC is identified by determining the lowest concentration of antibacterial agent that reduces the viability of the initial bacterial inoculum by ≥99.9%. Antibacterial agents are usually regarded as bactericidal if the MBC is no more than four times the MIC. It is worth noting that the MBC test uses colony-forming units as a measure of bacterial viability. This means the test can be confounded by antibacterial agents which cause aggregation of bacterial cells. Examples of antibacterial agents which do this include plant-derived compounds like flavonoids and peptides.
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