The treatment of choice for psittacosis pneumonia is which antibiotic?

• A. Amoxicillin
• B. Ciprofloxacin
• C. Trimethoprim/sulfamethoxazole
• D. Tetracycline

Answer: (D)

Psittacosis pneumonia is caused by Chlamydia psittaci, an intracellular bacterium, so the treatment must effectively reach and inhibit bacteria inside cells. Tetracyclines, such as doxycycline, excel here because they penetrate host cells and block protein synthesis by binding the 30S ribosomal subunit, providing reliable activity against Chlamydia species. This makes this class the preferred option. Amoxicillin targets cell-wall synthesis and isn’t effective against intracellular pathogens, so it’s not suitable. Ciprofloxacin can treat many bacteria but isn’t the first-line choice for psittacosis, and trimethoprim/sulfamethoxazole isn’t reliably active against Chlamydia psittaci. If tetracyclines are contraindicated, a macrolide like azithromycin can be used as an alternative.