In vitro activity of fosfomycin and other antimicrobials against uropathogenic Escherichia coli and Klebsiella pneumoniae at a tertiary care center in Lebanon.

BACKGROUND The incidence of urinary tract infections (UTIs) caused by extended-spectrum-beta-lactamase (ESBL) producing Escherichia coli (ESBL-EC) and Klebsiella pneumoniae (ESBL-KP) has been on the rise limiting oral treatment options. Fosfomycin was reported to be highly efficacious against these organisms, however, data is lacking in Lebanon and the Middle East. OBJECTIVE To determine the in vitro activity of fosfomycin against ESBL and non-ESBL-producing E. coli and K. pneumoniae uropathogens in Lebanon. METHODS A total of 542 consecutive non-duplicate isolates of ESBL-producing E. coli (n = 374) and K. pneumoniae (n = 168), and 291 isolates of non-ESBL-producing E. coli (n = 236) and K. pneumoniae (n = 55) were recovered from urine specimens of patients tested at the American University of Beirut Medical Center (AUBMC) during 2010. Each isolate was tested against a battery of 13 antimicrobials by disk diffusion according to the guidelines of CLSI testing and result interpretation criteria. RESULTS The fosfomycin susceptibility for ESBL-producing vs. non-ESBL-producing isolates was 86% vs. 97% for E. coli and 62% vs. 78% for K. pneumoniae. This activity of fosfomycin among ESBL-EC and ESBL-KP was generally higher than cefepime (26% & 30%), ciprofloxacin (24% & 41%), Trimeth/sulfa (26% & 19%), Pip/taz (75% and 45%), gentamicin (45% & 42%), and tobramycin (32% & 26%). On the other hand, higher activity against both species of ESBL-producing bacteria was shown by amikacin (96% & 79%) and imipenem (99.7% & 98.8%). Nitroflurantoin was highly active against ESBL-EC (95%) but not against ESBL-KP (29%). CONCLUSION Fosfomycin shows good activity, being higher against ESBL-producing E. coli than K. pneumoniae uropathogens in Lebanon.