title: Population analyses of the susceptibility to ciprofloxacin of eight clinical strains of Pseudomonas aeruginosa.
abstract: Population analyses of the susceptibility to ciprofloxacin of eight strains of Pseudomonas aeruginosa, including mucoid strains and strains resistant to aminoglycosides or anti-Pseudomonas beta-lactams, were carried out. All strains were sensitive as judged by the broth-dilution technique, but four strains were found to yield resistant mutants with a frequency of less than 10(-6). Two strains yielded mutants homogeneously sensitive to ciprofloxacin at a level 8-16 times the MIC of the parent strains. Two other strains yielded mutants resistant to different higher concentrations of ciprofloxacin. One of these mutants was examined for production of ciprofloxacin-inactivating enzyme; no enzyme production could be detected. Cross-resistance was found with another quinolone antibiotic, ofloxacin, but not with aminoglycosides or beta-lactam antibiotics.
mesh_terms: D002939:Ciprofloxacin; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D011804:Quinolines / Q000494:pharmacology*
chemical_list: D011804:Quinolines; D002939:Ciprofloxacin