Legionella pneumonia and penicillin sensitivity

• A. It is easily treated with penicillin G
• B. It does not respond to common penicillins
• C. It is resistant to macrolides
• D. It is not treatable with antibiotics

Answer: (B)

Legionella pneumonia involves bacteria that grow inside human cells, specifically macrophages. Because of this intracellular lifestyle, antibiotics need to penetrate cells effectively to reach the bacteria. Penicillins, including penicillin G, mainly target extracellular bacteria and have limited ability to enter and accumulate inside host cells, so they are not effective against Legionella. That’s why the statement that it does not respond to common penicillins is the best choice. In contrast, antibiotics with good intracellular activity, such as macrolides or fluoroquinolones, are effective against Legionella. It is not true that it’s resistant to all macrolides or that it’s untreatable, and penicillin G is not considered effective against Legionella.