Fosfomycin Susceptibilities Among Uropathogenic Extended Spectrum Beta-Lactamase-producing Enterobacteriacea
Methods: Retrospective review of urines cultures performed at Integrated Regional Laboratories (IRL) serving 14 acute care (ACF) and 5 long-term care facilities (LTCF) in South Florida between January 2013 and December 2013. Urine cultures were from hospitalized patients, emergency departments and residents in LTCF. Only Enterobacteriaceae isolates that tested non-susceptible to extended spectrum beta-lactam agents were included in the analysis. Isolates were considered to be ESBL-producing if they were intermediate (I), susceptible dose-dependent (SDD), or resistant (R) to any 3rd or 4th generation cephalosporin per the 2013 Clinical Laboratory Standards Institute (CLSI) breakpoints. Fosfomycin Kirby-Bauer disk diffusion susceptibilities were determined with a 200 ug disk using 2014 CLSI breakpoints: >16 S, 13-15 I, <12 R.
Results: ESBL-producing Enterobacteriaciae from 290 ACF and 87 LTCF urine cultures were analyzed. The number of E. coli isolates ranged from 3-35 in ACF and 2-40 in LTCF. 93% of isolates in ACF and 97% in LTCF were susceptible (Table). Klebsiella and Proteus strains were less susceptible than E. colistrains.
Table: Number and percent of urinary isolates susceptible to fosfomycin
Species ACF LTCF
E. coli 202/209 (97%) 75/76 (99%)
K. pneumoniae 60/70 (86%) 9/10 (90%)
K. oxytoca 4/4 (100%) No data
P. mirabilis 5/7 (71%) 0/1 (0%)
All 271/290 (93%) 84/87 (97%)
Conclusion: Fosfomycin has excellent in vitro activity against urinary ESBL-producing Enterobacteriacea strains, especially E. coli, in South Florida acute and long-term care facilities.
M. Tysiak, None
T. M. Hooton, None