[In vitro activity of fluoroquinolones and oral beta lactam antibiotics against clinical isolates of Escherichia coli].

We studied the in vitro activity of amoxicillin-clavulanic acid, cefprozil, cefuroxime, cefpodoxime, ceftibuten, cefixime, ciprofloxacin and sparfloxacin against 400 strains of Escherichia coli. The strains were obtained from urine cultures from patients with community acquired urinary tract infection who were treated in our hospital in 1997 and 1998. Among the six betalactams, ceftibuten and cefixime were the most active in vitro with MIC90 of 0.5 mg/l. Both antimicrobials were 2- and 16-fold more active than cefpodoxime (MIC90 1 mg/l) and cefprozil (MIC90 8 mg/l), respectively. However, overall, the four cephalosporins inhibited between 95% and 99% of isolates. Cefuroxime and amoxicillin-clavulanic acid showed less activity with a MIC90 of 16 mg/l. The percentage of fluoroquinolone-resistant strains was 24% with a similar activity to ciprofloxacin (MIC90 32 mg/l) and sparfloxacin (MIC90 64 mg/l).