Minimum bactericidal concentration

Minimum Bactericidal Concentration (MBC) is a term used in Microbiology to denote the lowest concentration of an Antimicrobial agent that results in microbial death. It is a key parameter in the field of Antimicrobial susceptibility testing.

Definition

The Minimum Bactericidal Concentration is defined as the lowest concentration of an antimicrobial agent that kills a particular bacterium. It is usually expressed in Micrograms per milliliter (µg/mL) or milligrams per liter (mg/L). The MBC is determined after the bacteria have been exposed to the antimicrobial agent for a specific period, typically 18-24 hours.

Determination

The MBC is determined by subculturing samples from the Minimum inhibitory concentration (MIC) test to agar plates that do not contain the test agent. The plates are then incubated for 24 hours and the colonies are counted. The MBC is the lowest concentration of the antimicrobial agent at which 99.9% of the initial bacterial population is killed.

Clinical Significance

The MBC is used in the clinical setting to guide the selection of appropriate antimicrobial therapy. It provides information on the bactericidal activity of a drug and can help predict its efficacy in vivo. The MBC is particularly important in the treatment of infections caused by organisms that are difficult to eradicate, such as Mycobacterium tuberculosis and Staphylococcus aureus.

See Also

• Minimum inhibitory concentration
• Antimicrobial susceptibility testing
• Antimicrobial resistance

References

• Andrews, J. M. (2001). Determination of minimum inhibitory concentrations. Journal of Antimicrobial Chemotherapy, 48(suppl_1), 5-16.
• Wiegand, I., Hilpert, K., & Hancock, R. E. (2008). Agar and broth dilution methods to determine the minimal inhibitory concentration (MIC) of antimicrobial substances. Nature protocols, 3(2), 163-175.