Infected cysts in ADPKD are treated with which antibiotic therapy?

• A. Penicillin
• B. Aztreonam
• C. Vancomycin
• D. Ciprofloxacin

Answer: (D)

Treating infected cysts in ADPKD hinges on using an antibiotic that reaches adequate concentrations inside the cyst fluid. Ciprofloxacin shines here because it penetrates cysts well and achieves cyst-fluid levels that can suppress common causative bacteria such as Gram-negative rods (for example, E. coli and related Enterobacterales). Its oral bioavailability also allows easy transition from IV to oral therapy, which is convenient for longer courses as often required for cyst infections. In contrast, penicillins generally do not achieve reliable cyst penetration; vancomycin mainly targets Gram-positives and has limited cyst penetration; and aztreonam, while active against Gram-negative rods, does not have as reliable penetration into cysts as fluoroquinolones. Therefore, ciprofloxacin is the best choice for infected cysts in ADPKD.