American Board of Internal Medicine (ABIM) Certification Practice Exam

Which is the first-line antibiotic for treating streptococcal throat infections?

1. Amoxicillin

2. Ciprofloxacin

3. Penicillin

4. Erythromycin

The correct answer is: Penicillin

The first-line antibiotic for treating streptococcal throat infections is Penicillin. Streptococcal pharyngitis, commonly known as strep throat, is most frequently caused by Group A Streptococcus (GAS), and Penicillin is particularly effective against these bacteria due to its action against the cell wall synthesis of the organism. Given its efficacy, Penicillin is widely recommended due to its narrow spectrum, which reduces the likelihood of disrupting normal flora and the development of antibiotic resistance. It typically has a good safety profile, is affordable, and has been used for many years as a gold standard treatment option. Amoxicillin may also be used as an alternative in certain cases, especially for patients who have difficulty swallowing pills, but Penicillin remains the preferred choice for the standard treatment of strep throat. Ciprofloxacin is not suitable for this type of infection as it is a fluoroquinolone antibiotic that is more appropriate for Gram-negative infections and other specific indications. Erythromycin may be used as an alternative for patients with a penicillin allergy, but it is not the first-line choice. Therefore, Penicillin is established as the most appropriate first-line treatment for streptococcal throat infections.