title: Resistance of Pseudomonas to quaternary ammonium compounds. II. Cross-resistance characteristics of a mutant of Pseudomonas aeruginosa.
abstract: Tube dilution experiments showed that benzalkonium chloride (BC)-resistant mutants of Pseudomonas aeruginosa grown in the presence of 1,000 mug of BC per ml were at least 20 times more sensitive to polymyxin B and colistin sulfate than the BC-sensitive (BCS) parent strain. BCS cells selected for resistance to 500 mug of polymyxin B per ml remained sensitive to BC. There was little difference in the amount of carbenicillin, gentamicin sulfate, or rifampin needed to prevent growth of either the BCS or BC-resistant (BCR) strains. Growth of BCR cells was inhibited by ethylenediaminetetraacetate at a concentration of 400 mug/ml or less, whereas the BCS strain grew at ethylenediaminetetraacetate levels of 10,000 mug/ml. Phenylmercuric acetate and thimerosal inhibited growth of BCR and BCS cells at concentrations of 10 mug/ml or less. BCR cells were cross-resistant to >1,000 mug/ml concentrations of five other quaternary ammonium compounds, including three with C(16) alkyls and two with alkyl groups of shorter length. The BCS strain was also resistant to >1,000 mug/ml concentrations of the three quaternary ammonium compounds with C(16) alkyl groups but, in addition to BC, was inhibited by 200 mug/ml levels or less of the two quaternary ammonium compounds containing alkyl groups of less than 16 carbon atoms.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D055598:Chemical Phenomena; D002621:Chemistry; D003470:Culture Media; D004352:Drug Resistance, Microbial; D004357:Drug Synergism; D004492:Edetic Acid / Q000494:pharmacology; D005827:Genetics, Microbial; D008826:Microbial Sensitivity Tests; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000900:Anti-Bacterial Agents; D001548:Benzalkonium Compounds; D003470:Culture Media; D004492:Edetic Acid