Briales, ARodríguez-Martínez, J MVelasco, CDíaz de Alba, PDomínguez-Herrera, JPachón, JPascual, A2016-08-102016-08-102011-03Briales A, Rodríguez-Martínez JM, Velasco C, Díaz de Alba P, Domínguez-Herrera J, Pachón J, et al. In vitro effect of qnrA1, qnrB1, and qnrS1 genes on fluoroquinolone activity against isogenic Escherichia coli isolates with mutations in gyrA and parC. Antimicrob. Agents Chemother. 2011; 55(3):1266-90066-4804http://hdl.handle.net/10668/2364Journal Article; Research Support, Non-U.S. Gov't;This article provides an analysis of the in vitro effect of qnrA1, qnrB1, and qnrS1 genes, combined with quinolone-resistant Ser83Leu substitutions in GyrA and/or Ser80Arg in ParC, on fluoroquinolone (FQ) resistance in isogenic Escherichia coli strains. The association of Ser83Leu substitution in GyrA, Ser80Arg substitution in ParC, and qnr gene expression increased the MIC of ciprofloxacin to 2 μg/ml. qnr genes present in E. coli that harbored a Ser83Leu substitution in GyrA increased mutant prevention concentration (MPC) values to 8 to 32 μg/ml. qnr gene expression in E. coli may play an important role in selecting for one-step FQ-resistant mutants.enPruebas de sensibilidad microbianaMutaciónCiprofloxacinoMedical Subject Headings::Chemicals and Drugs::Enzymes and Coenzymes::Enzymes::Isomerases::DNA Topoisomerases::DNA Topoisomerases, Type II::DNA GyraseMedical Subject Headings::Chemicals and Drugs::Enzymes and Coenzymes::Enzymes::Isomerases::DNA Topoisomerases::DNA Topoisomerases, Type II::DNA Topoisomerase IVMedical Subject Headings::Organisms::Bacteria::Gram-Negative Bacteria::Gram-Negative Facultatively Anaerobic Rods::Enterobacteriaceae::Escherichia::Escherichia coliMedical Subject Headings::Chemicals and Drugs::Amino Acids, Peptides, and Proteins::Proteins::Bacterial Proteins::Escherichia coli ProteinsMedical Subject Headings::Chemicals and Drugs::Heterocyclic Compounds::Heterocyclic Compounds, 2-Ring::Quinolines::Quinolones::FluoroquinolonesMedical Subject Headings::Analytical, Diagnostic and Therapeutic Techniques and Equipment::Diagnosis::Diagnostic Techniques and Procedures::Clinical Laboratory Techniques::Microbiological Techniques::Microbial Sensitivity TestsMedical Subject Headings::Phenomena and Processes::Genetic Phenomena::Genetic Variation::MutationMedical Subject Headings::Chemicals and Drugs::Heterocyclic Compounds::Heterocyclic Compounds, 2-Ring::Quinolines::Quinolones::Fluoroquinolones::Ciprofloxacinresearch article21173174open access10.1128/AAC.00927-101098-6596PMC3067081