In vitro susceptibility of aerobic gram-negative blood culture isolates to oxolinic acid, norfloxacin, ciprofloxacin, enoxacin, pefloxacin, ofloxacin and oxo-enoxacin.

100 gram-negative strains isolated from blood cultures were selected for the evaluation of the in vitro activity of oxolinic acid, norfloxacin, ciprofloxacin, enoxacin, pefloxacin, ofloxacin and oxo-enoxacin. Ciprofloxacin showed the highest intrinsic activity. Oxo-enoxacin, the major metabolite of enoxacin, was 10-15-fold less active than enoxacin. Against Enterobacteriaceae and Vibrionaceae, all fluorinated quinolones except norfloxacin were equally effective, while against non-fermenters, ciprofloxacin and ofloxacin demonstrated greater activity than the others. Resistance to oxolinic acid had a detrimental effect on susceptibility to the new fluorinated quinolones.