Minimal bactericidal concentration (MBC)

Definition

Minimal bactericidal concentration (MBC) is the lowest concentration of an antimicrobial agent required to kill a particular bacterium. It is determined after identifying the minimum inhibitory concentration (MIC).

5 Must Know Facts For Your Next Test

1. The MBC test is performed after determining the MIC to further assess the effectiveness of an antimicrobial.
2. MBC is usually higher than MIC since it measures bactericidal activity rather than just inhibition.
3. Determining MBC involves culturing bacteria from non-growing wells in a MIC assay and checking for colony formation.
4. MBC values are critical in treating infections where bacterial eradication is necessary, such as endocarditis.
5. A ratio of MBC to MIC greater than 4 indicates that the antimicrobial is more bacteriostatic than bactericidal.

Review Questions

• What is the purpose of determining the Minimal Bactericidal Concentration (MBC)?
• How does MBC differ from MIC in terms of evaluating antimicrobial effectiveness?
• Why might a clinician prefer using MBC values over MIC values for certain infections?

Related terms

Minimum Inhibitory Concentration (MIC):

The lowest concentration of an antimicrobial agent that inhibits visible growth of a microorganism.

Bacteriostatic:

Refers to agents that inhibit bacterial growth without necessarily killing the bacteria.

Bactericidal:

Refers to agents that kill bacteria outright rather than merely inhibiting their growth.