Provide an example of antibiotic synergy.

• A. Penicillin (e.g., ampicillin) with an aminoglycoside (e.g., gentamicin) showing enhanced activity against certain bacteria.
• B. Penicillin alone is sufficient for all bacteria.
• C. Tetracycline with penicillin always shows synergy.
• D. Aminoglycoside with vancomycin always inhibits all bacteria without synergy.

Answer: (A)

Antibiotic synergy occurs when two drugs used together produce a greater bactericidal effect than either would alone because they complement each other’s actions. A classic example is combining a beta-lactam like penicillin with an aminoglycoside such as gentamicin. Penicillin disrupts cell wall synthesis, weakening the bacterial cell and allowing the aminoglycoside to enter more easily and inhibit protein synthesis, leading to stronger killing. This cooperative effect is especially useful against certain bacteria where penicillin alone isn’t fully effective.

Penicillin alone isn’t sufficient for all bacteria, and not every drug pair yields synergy. For instance, tetracycline with penicillin does not reliably produce a synergistic effect in all organisms, and pairing an aminoglycoside with vancomycin is not universally synergistic or guaranteed to inhibit all bacteria.