Which antibiotic is indicated for treating an aerobic mixed infection insensitive to penicillin?

• A. Amoxicillin
• B. Penicillin VK
• C. Tetracycline
• D. Erythromycin

Answer: (A)

The main idea is using a broad-spectrum penicillin with good tissue penetration to cover the variety of aerobes found in a mixed dental infection, especially when penicillin alone might not be sufficient. Amoxicillin stands out because it is better absorbed orally and achieves higher and more consistent serum and tissue levels than penicillin VK. This helps ensure adequate concentrations in inflamed dental and periodontal tissues and in mixed infections where multiple aerobic organisms are involved, increasing the likelihood of effective coverage.

Penicillin VK is narrower in spectrum and has less favorable absorption, making it less reliable for a mixed aerobic infection. Tetracycline and erythromycin can be alternatives, but they come with more potential for adverse effects, interactions, and resistance concerns in dental practice. Therefore, amoxicillin is typically preferred when a broad-coverage penicillin is indicated for an aerobic mixed infection that isn’t fully susceptible to penicillin.