Fosfomycin for the Treatment of Cystitis in the Abdominal Solid Organ Transplant Population

Study objectives: To evaluate the use of fosfomycin (FOS) at the single-dose regimen approved by the U.S. Food and Drug Administration as well as off-label multidose regimens for the treatment of cystitis after abdominal solid organ transplant (aSOT).

Design: Retrospective study.

Setting: Tertiary academic medical center.

Patients: Adult inpatients with history of aSOT receiving FOS between January 1, 2009, and April 30, 2015, for the treatment of cystitis.

Measurements and main results: Seventy-six courses of FOS were identified in 64 patients. Overall treatment success was 85.5%, with 11 failed treatment courses. Enterococcus was isolated in 59.3% of courses, of which 72.2% were vancomycin-resistant enterococci (VRE). Gram-negative organisms comprised a quarter of isolated bacteria, with most resistant to three or more antimicrobial classes. In the 11 failed treatment courses, 90% were targeted against enterococcus, of which 82% were VRE. Six of these failures (54%) were successfully retreated with uroselective therapy (FOS or nitrofurantoin). No significant difference in the success rate of single-dose versus multidose therapy was seen (80.6% vs 90%, p=0.33). Concomitant systemic antibiotics for other indications were present in 36.8% of courses, and they were significantly more frequent in the multidose group (67.5% vs 47.2%, p=0.04). However, multivariable logistic regression analysis found that after adjustment for broad-spectrum antibiotic use, no statistically significant difference in failure rates was found between the two regimens (p=0.42).

Conclusion: FOS appears to be successful in the treatment of cystitis in aSOT recipients. Multidose therapy did not significantly improve success over a single-dose regimen. Further prospective studies are needed to elucidate the true efficacy of FOS in the aSOT population.