Fosfomycin monotherapy for the treatment of a complicated prostatic abscess caused by KPC-producing carbapenem-resistant Escherichia coli

ABSTRACT Background Prostatic abscess caused by carbapenem-resistant Escherichia coli (CREC) is an uncommon but serious infection with limited therapeutic options, particularly when prolonged antimicrobial therapy and oral step-down treatment are required. Evidence supporting fosfomycin monotherapy for prostatic abscess caused by CREC remains scarce. Case Summary A 67-year-old man with diabetes mellitus and prolonged corticosteroid exposure presented with severe sepsis secondary to a multiloculated prostatic abscess measuring 57.2 × 38.7 × 49.4 mm. Urine and abscess cultures yielded KPC-producing CREC susceptible to fosfomycin (MIC = 0.25 μg/mL) and amikacin. Because access to newer β-lactam/β-lactamase inhibitor agents was limited, treatment was initiated with intravenous fosfomycin plus amikacin. Amikacin was discontinued after 2 days because of nephrotoxicity, and therapy was successfully continued with intravenous fosfomycin monotherapy following transperineal ultrasound-guided abscess drainage. The patient received intravenous fosfomycin 6 g every 8 h for 21 days, followed by oral fosfomycin calcium 3 g every 24 h for 30 days, with complete clinical and radiological resolution, and no relapse during 6 months of follow-up. Conclusion Although the initial brief course of amikacin may have contributed to early bacterial clearance, the majority of treatment was administered as fosfomycin monotherapy after adequate source control. This case suggests that antibiotic susceptibility test-guided fosfomycin monotherapy, combined with adequate drainage, is a feasible treatment for prostatic abscesses caused by CREC, particularly in resource-limited settings.