Which statement about chlorhexidine's concentration-dependent effects is true?

Which statement about chlorhexidine's concentration-dependent effects is true?

• A. It is bactericidal at all concentrations
• B. It is bacteriostatic at low concentrations and bactericidal at high concentrations
• C. It has no antimicrobial effect
• D. It requires a high pH to be active

Answer: (B)

Chlorhexidine has concentration-dependent antimicrobial effects: at low concentrations it inhibits bacterial growth (bacteriostatic) by binding to the bacterial cell wall and causing reversible disruption of the cell membrane, which slows metabolism without immediately killing the cell. At higher concentrations, the disruption becomes more severe, leading to leakage of cellular contents and actual cell death (bactericidal). This explains why the statement describing it as bacteriostatic at low concentrations and bactericidal at high concentrations is the best choice. It’s not accurate to say it’s bactericidal at all concentrations, it does have antimicrobial activity across concentrations, and its activity isn’t dependent on a high pH.

Chlorhexidine has concentration-dependent antimicrobial effects: at low concentrations it inhibits bacterial growth (bacteriostatic) by binding to the bacterial cell wall and causing reversible disruption of the cell membrane, which slows metabolism without immediately killing the cell. At higher concentrations, the disruption becomes more severe, leading to leakage of cellular contents and actual cell death (bactericidal). This explains why the statement describing it as bacteriostatic at low concentrations and bactericidal at high concentrations is the best choice. It’s not accurate to say it’s bactericidal at all concentrations, it does have antimicrobial activity across concentrations, and its activity isn’t dependent on a high pH.