The efficacy of fosfomycin for treatment of cystitis in abdominal transplant recipients

Introduction: Increased use of antimicrobial prophylaxis following abdominal solid organ transplant (aSOT) has resulted in the emergence of multidrug resistant organisms. Fosfomycin (FOS) is FDA approved for the treatment of uncomplicated urinary tract infections in women. Literature supports in vitro efficacy against MDR pathogens including vancomycin resistant enterococci (VRE). However, limited data supports the clinical efficacy of FOS in aSOT. 

Objectives: This study aims to investigate the efficacy of FOS for the treatment of cystitis in the aSOT population.

Study Design: Retrospective

Methods: Chart review of adult aSOT receiving FOS from 1/1/2007–1/1/2013.

Results: Seventy-six courses of targeted therapy with FOS were identified in 64 patients. Renal transplant recipients accounted for 74% of courses.   Patients with urinary foreign body placement accounted for 40% of courses, 20% were ureteral stents. The overall rate of treatment success was 85.5%.  Enterococcus was isolated in 59% of courses, 72.2% of these were VRE. In 22% of courses FOS was used for the treatment of gram-negative organisms. Concomitant systemic antibiotics for other indications were present in 36.8% of courses.  In the 11 failed treatment courses, 90% were targeted against enterococcus, of which 82% were VRE.  Six of these failures were then successfully retreated with nonsystemic therapy (FOS or nitrofurantoin). A subgroup analysis was conducted comparing single dose therapy (n=36) against multidose therapy (n=40) in a matched cohort of courses. There was no difference in the success rate of single dose therapy versus multidose therapy (80.6% vs 90%, p=0.24). However, concomitant systemic antimicrobial therapy was more common in the multidose group (70% vs 47.2%, p 0.04), possibly suggesting selection bias toward multidose for more subjectively ill individuals. 

Conclusions: FOS appears to be efficacious for the treatment of cystis in aSOT recipients. In this study, single dose was non-inferior to multidose therapy.