Comparative determination of minimal inhibitory and bactericidal concentrations of ciprofloxacin, cefotaxime and HR 810 for gram-negative bacteria either sensitive or resistant to ureidopenicillins and/or gentamicin.

The minimal inhibitory (MIC) and minimal bactericidal (MBC) concentrations of ciprofloxacin were compared with those of the cephalosporins HR 810 and cefotaxime in 250 strains from 10 species of Gram-negative bacteria with sensitivity or resistance to gentamicin and/or piperacillin. Ciprofloxacin had an inhibitory activity higher than, or practically equal to the best of the two cephalosporins. The MBC of ciprofloxacin was more often less than or equal to twice the MIC than with the beta-lactam antibiotics. Parallel resistance was found with pipemidic acid as representative of DNA-gyrase inhibitors. No direct parallel resistance was observed with resistance to gentamicin, piperacillin or cefotaxime.