title: Resistance to ciprofloxacin appearing during therapy.
abstract: The development of resistance to ciprofloxacin in nine clinical isolates of Pseudomonas aeruginosa was investigated. Isolates had increases in minimal inhibitory concentrations (MICs) from 0.25 to 16 micrograms/ml. The isolates also became resistant to ofloxacin and norfloxacin, but did not show increases in MICs to aminoglycosides, antipseudomonas penicillins, or cephalosporins. One isolate from a patient with endocarditis showed a reduction in a 43-kD outer membrane protein and simultaneous increase in the imipenem MIC. This isolate also showed impaired uptake of ciprofloxacin. Respiratory isolates from cystic fibrosis patients did not show loss of outer membrane protein. MICs were lowered by ethylene diaminetetra-acetic acid, suggesting changes in lipopolysaccharide. Resistant isolates were synergistically inhibited by combinations of ciprofloxacin plus tobramycin or ceftazidime, but MICs remained beyond the achievable serum level.
authors.affiliation: Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York 10032.
authors.forename: N X
authors.initials: NX
authors.lastname: Chin
authors.forename: N
authors.initials: N
authors.lastname: Clynes
authors.forename: H C
authors.initials: HC
authors.lastname: Neu
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D002939:Ciprofloxacin / Q000494:pharmacology* / Q000627:therapeutic use; D004352:Drug Resistance, Microbial; D006801:Humans; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000032:analysis / Q000187:drug effects*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002939:Ciprofloxacin