According to the experimental results, which antibiotic was less effective against Staphylococcus epidermidis?

According to the experimental results, which antibiotic was less effective against Staphylococcus epidermidis?

• A. Penicillin
• B. Novobiocin
• C. Gentamicin
• D. Neither Penicillin nor the others were less effective

Answer: (A)

Penicillin is often less effective against Staphylococcus epidermidis because this species commonly produces beta-lactamase, an enzyme that inactivates penicillin by breaking the beta-lactam ring. In a susceptibility test, beta-lactamase activity manifests as a small or absent zone of inhibition around a penicillin disk, indicating poor antibiotic activity. By comparison, novobiocin and gentamicin typically show clearer inhibition in these tests against S. epidermidis, reflecting better effectiveness for those agents in the same experimental context. So the data would support penicillin as the less effective option.

Penicillin is often less effective against Staphylococcus epidermidis because this species commonly produces beta-lactamase, an enzyme that inactivates penicillin by breaking the beta-lactam ring. In a susceptibility test, beta-lactamase activity manifests as a small or absent zone of inhibition around a penicillin disk, indicating poor antibiotic activity. By comparison, novobiocin and gentamicin typically show clearer inhibition in these tests against S. epidermidis, reflecting better effectiveness for those agents in the same experimental context. So the data would support penicillin as the less effective option.