Which statement correctly describes chlorhexidine's antibacterial activity at different concentrations?

Which statement correctly describes chlorhexidine's antibacterial activity at different concentrations?

• A. It is bacteriostatic at low concentrations and bactericidal at high concentrations
• B. It is bactericidal at all concentrations
• C. It has no antimicrobial effect
• D. It requires ultraviolet light to activate

Answer: (A)

Chlorhexidine’s antibacterial action depends on how much of it is present. At low concentrations it mainly slows or stops growth, making it bacteriostatic by binding to the bacterial surface and altering membrane function enough to inhibit essential processes but not necessarily kill the cell. When the concentration is higher, it disrupts the cell membrane more aggressively, causing leakage of cellular contents and rapid cell death, which is bactericidal. It acts on contact and doesn’t require any light to become active. This is why the statement describing a switch from bacteriostatic at low concentrations to bactericidal at high concentrations is the best description.

Chlorhexidine’s antibacterial action depends on how much of it is present. At low concentrations it mainly slows or stops growth, making it bacteriostatic by binding to the bacterial surface and altering membrane function enough to inhibit essential processes but not necessarily kill the cell. When the concentration is higher, it disrupts the cell membrane more aggressively, causing leakage of cellular contents and rapid cell death, which is bactericidal. It acts on contact and doesn’t require any light to become active. This is why the statement describing a switch from bacteriostatic at low concentrations to bactericidal at high concentrations is the best description.