Methods: A retrospective chart review was conducted on patients who received at least one dose of oral fosfomycin for a UTI caused by a Gram-negative organism. Clinical response was classified as favorable, unfavorable, or uncertain. Microbiological response was defined as cured, presumed cured, or failed. For patients whose bacterial isolate was available, susceptibility of fosfomycin was determined using the disk diffusion method performed and interpreted according to Clinical Laboratory Standards Institute (CLSI) recommendations
Results: Seventy-three patients received fosfomycin from January 2005-April 2014. Fifty (68.5%) of patients achieved a favorable clinical response. As for microbiological response, the results were similar; fifty patients attained a cure or presumed cure. Veterans with an E. coli infection achieved a favorable response rate of 80%, whereas veterans with a P. aeruginosa or K. pneumoniae infection only achieved a favorable response rate of 61.5% and 60%, respectively. Fosfomycin susceptibility was determined on twenty-two isolates (9 Klebsiella pneumoniae, 8 Escherichia coli, 5 Pseudomonas aeruginosa). All isolates were susceptible according to CLSI disk diffusion breakpoints except for two K. pneumoniae isolates.
Conclusion: Fosfomycin has retained activity against many Gram-negative organisms; achieving fair clinical and microbiological response rates. Fosfomycin appears to be most efficacious in E. coli UTIs. Further study is needed to clarify the microbiological and clinical determinants of therapeutic failure.
C. Burant, None
S. Sims, None