BACKGROUND: Uropathogenic Escherichia coli (UPEC) is a major cause of Urinary 
Tract Infections (UTIs). Due to increasing antibiotic-resistance among UPEC 
bacteria, new treatment options for UTIs are urgently needed.
OBJECTIVE: To identify new agents targeting growing bacteria that may be used 
for the treatment of antibiotic-resistant UTIs.
METHODS: We screened a clinical compound library consisting of 1,524 compounds 
using a high throughput 96-well plate assay and ranked the activities of the 
selected agents according to their MICs against the UPEC strain UTI89.
RESULTS: We identified 33 antibiotics which were active against log-phase 
clinical UPEC strain UTI89. Among the selected antibiotics, there were 12 
fluoroquinolone antibiotics (tosufloxacin, levofloxacin, sparfloxacin, 
clinafloxacin, pazufloxacin, gatifloxacin, enrofloxacin, lomefloxacin, 
norfloxacin, fleroxacin, flumequine, ciprofloxacin), 15 beta-lactam or 
cephalosporin antibiotics (cefmenoxime, cefotaxime, ceftizoxime, cefotiam, 
cefdinir, cefoperazone, cefpiramide, cefamandole, cefixime, ceftibuten, 
cefmetazole, cephalosporin C, aztreonam, piperacillintazobactam, mezlocillin), 3 
tetracycline antibiotics (meclocycline, doxycycline, tetracycline), 2 
membrane-acting agents (colistin and clofoctol), and 1 protein synthesis 
inhibitor (amikacin). Among them, the top 7 hits were colistin, tosufloxacin, 
levofloxacin, sparfloxacin, clinafloxacin, cefmenoxime and pazufloxacin, where 
clinafloxacin and pazufloxacin were the newly identified agents active against 
UPEC strain UTI89. We validated the key results obtained with UTI89 on two other 
UTI strains CFT073 and KTE181 and found that they all had comparable MICs for 
fluoroquinolones while CFT073 and KTE181 were more susceptible to cephalosporin 
antibiotics and tetracycline antibiotics but were less susceptible to colistin 
than UTI89.
CONCLUSION: Our findings provide possible effective drug candidates for the more 
effective treatment of antibiotic-resistant UTIs.