In vitro activity of flomoxef against extended-spectrum ß-lactamase-producing Escherichia coli and Klebsiella pneumoniae in Korea.

To find an alternative regimen for the treatment of extended-spectrum ß-lactamase (EBSL)-producing Enterobacteriaceae infections, we examined the in vitro activity of flomoxef against Escherichia coli and Klebsiella pneumoniae having CTX-M-1 group and/or CTX-M-9 group ESBLs. Boronic acid disk methods and polymerase chain reaction amplification were used to detect for ESBL, and AmpC ß-lactamase and AmpC ß-lactamase co-producers were excluded. Minimum inhibitory concentrations (MICs) were determined for flomoxef by broth microdilution. One hundred seventy-six isolates (E. coli, n = 93 and K. pneumoniae, n = 83) were analyzed for susceptibility test. A total of 94.3% (166/176) of isolates were susceptible to flomoxef (MIC50/MIC90 were 0.5/8 µg/mL); 98.9% of the ESBL-producing E. coli (MIC50/MIC90 were 1/4 µg/mL) and 89.2% of the ESBL-producing K. pneumoniae (MIC50/MIC90 were 0.5/16 µg/mL) were susceptible to flomoxef. Flomoxef has good in vitro activity against ESBL-producing E. coli and K. pneumoniae and could be considered as an alternative for infections caused by these organisms.