For native valve infective endocarditis caused by susceptible streptococci, which is listed as a treatment option?

For native valve infective endocarditis caused by susceptible streptococci, which is listed as a treatment option?

• A. Doxycycline
• B. Azithromycin
• C. Penicillin
• D. Vancomycin

Answer: (C)

Penicillin is the best choice because, when native-valve endocarditis is caused by streptococci that are susceptible to penicillin, this drug is highly effective and bactericidal against these organisms. High-dose penicillin G (often given IV for several weeks) achieves reliable levels in blood and in the abnormal valve vegetation, leading to rapid and complete eradication of the infection. Doxycycline or azithromycin are less reliable here due to variable susceptibility and higher rates of resistance among streptococci, and are not preferred as first-line monotherapy for susceptible strains. Vancomycin is reserved for cases where penicillin cannot be used (such as true penicillin allergy or resistant organisms) or when broader coverage is required, not for standard susceptible streptococcal IE.

Penicillin is the best choice because, when native-valve endocarditis is caused by streptococci that are susceptible to penicillin, this drug is highly effective and bactericidal against these organisms. High-dose penicillin G (often given IV for several weeks) achieves reliable levels in blood and in the abnormal valve vegetation, leading to rapid and complete eradication of the infection. Doxycycline or azithromycin are less reliable here due to variable susceptibility and higher rates of resistance among streptococci, and are not preferred as first-line monotherapy for susceptible strains. Vancomycin is reserved for cases where penicillin cannot be used (such as true penicillin allergy or resistant organisms) or when broader coverage is required, not for standard susceptible streptococcal IE.