title: Emergence of carbapenem resistance due to the novel insertion sequence ISPa8 in Pseudomonas aeruginosa.
abstract: Chronic lung infections due to the persistence of Pseudomonas aeruginosa in cystic fibrosis patients are typically associated with the emergence of antibiotic resistance. The purpose of this study was to investigate the mechanisms responsible for the emergence of carbapenem resistance when a clinical isolate of P. aeruginosa collected from a patient with cystic fibrosis was challenged with meropenem. Nine carbapenem-resistant mutants were selected with subinhibitory concentrations of meropenem from a clinical isolate of P. aeruginosa and characterized for carbapenem resistance. Increased carbapenem MICs were associated with the identification of the novel insertion sequence ISPa8 within oprD or its promoter region in all the mutants. The position of ISPa8 was different for each of the mutants evaluated. In addition, Southern blot analyses identified multiple copies of ISPa8 within the genomes of the mutants and their parent isolate. These data demonstrate that transposition of IS elements within the Pseudomonas genome can influence antibiotic susceptibility. Understanding the selective pressures associated with the emergence of antibiotic resistance is critical for the judicious use of antimicrobial chemotherapy and the successful treatment of bacterial infections.
authors.affiliation: Creighton University School of Medicine, Department of Medical Microbiology and Immunology, Center for Research in Anti-Infectives and Biotechnology, Omaha, Nebraska, United States of America.
authors.forename: Randal C
authors.initials: RC
authors.lastname: Fowler
authors.affiliation: Creighton University School of Medicine, Department of Medical Microbiology and Immunology, Center for Research in Anti-Infectives and Biotechnology, Omaha, Nebraska, United States of America.
authors.forename: Nancy D
authors.initials: ND
authors.lastname: Hanson
mesh_terms: D001483:Base Sequence; D015139:Blotting, Southern; D015780:Carbapenems / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D004352:Drug Resistance, Microbial / Q000187:drug effects / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D016254:Mutagenesis, Insertional / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D016133:Polymerase Chain Reaction; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D013845:Thienamycins / Q000494:pharmacology
chemical_list: D015780:Carbapenems; D013845:Thienamycins; D000077731:Meropenem