The minimum bactericidal concentration (MBC) of an antibiotic is defined as the lowest concentration that:
- A Inhibits visible growth of the organism after 24 hours
- B Kills 50% of the initial bacterial inoculum
- C Kills 99.9% of the initial bacterial inoculum ✓
- D Produces a zone of inhibition of at least 15 mm on agar
Correct answer: C. Kills 99.9% of the initial bacterial inoculum
Explanation
MBC is defined as the lowest antibiotic concentration killing 99.9% of the initial inoculum. Option A describes MIC. Option B is not a standard definition. Option D describes a disk diffusion zone diameter, unrelated to MBC. The 99.9% cutoff is the internationally accepted CLSI and EUCAST standard for defining bactericidal activity.
Reference: Bailey and Love's Short Practice of Surgery, 28th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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