Sublethal Antibiotic Treatment Leads to Multidrug Resistance via Radical-Induced Mutagenesis  Michael A. Kohanski, Mark A. DePristo, James J. Collins  Molecular Cell  Volume 37, Issue 3, Pages 311-320 (February 2010) DOI: 10.1016/j.molcel.2010.01.003 Copyright © 2010 Elsevier Inc. Terms and Conditions

Molecular Cell 2010 37, 311-320DOI: (10.1016/j.molcel.2010.01.003) Copyright © 2010 Elsevier Inc. Terms and Conditions

Figure 1 Low Levels of Bactericidal Antibiotics Increase Mutation Rate Due to Reactive Oxygen Species Formation (A) Fold change in mutation rate (mean ±95% confidence interval [CI]) relative to an untreated control (no drug) for wild-type E. coli (MG1655) following an overnight treatment with 1 μg/ml ampicillin, 1 μg/ml kanamycin, 3 μg/ml kanamycin, 15 ng/ml norfloxacin, 50 ng/ml norfloxacin, or 1 mM hydrogen peroxide (H2O2). (B) Correlation between oxidative stress levels (HPF fluorescence) and fold change in mutation rate for wild-type E. coli for the treatments described in (A). (C and D) Fold change in mutation rate (mean ±95% CI) relative to an untreated control (no drug) for wild-type E. coli following an overnight treatment with 100 mM thiourea and no drug, 1 μg/ml ampicillin, 1 μg/ml kanamycin, 3 μg/ml kanamycin, 15 ng/ml norfloxacin, 50 ng/ml norfloxacin, or 1 mM hydrogen peroxide (H2O2) under aerobic growth conditions with 100 mM thiourea (C) or anaerobic growth conditions (D). See also Figure S2. Molecular Cell 2010 37, 311-320DOI: (10.1016/j.molcel.2010.01.003) Copyright © 2010 Elsevier Inc. Terms and Conditions

Figure 2 Low Levels of Bactericidal Antibiotics Can Lead to Broad-Spectrum Increases in MIC Due to ROS-Mediated Mutagenesis (A and B) Fold change in MIC relative to an aerobic no-drug control for ampicillin, norfloxacin, kanamycin, tetracycline, and chloramphenicol, following 5 days of growth in the presence of 1 μg/ml ampicillin under aerobic (A) or anaerobic (B) growth conditions. See also Figure S1. Molecular Cell 2010 37, 311-320DOI: (10.1016/j.molcel.2010.01.003) Copyright © 2010 Elsevier Inc. Terms and Conditions

Figure 3 Ampicillin Treatment of E. coli Results in Heterogeneous Increases in MIC for Ampicillin and Norfloxacin (A and B) Shown are the distributions of ampicillin (A) or norfloxacin (B) MICs for 44 ampicillin-treated isolates. The maximum growth-inhibitory concentration tested for norfloxacin was 1000 ng/ml, and the MICs for these isolates may be ≥1000 ng/ml. Molecular Cell 2010 37, 311-320DOI: (10.1016/j.molcel.2010.01.003) Copyright © 2010 Elsevier Inc. Terms and Conditions

Figure 4 Ampicillin Treatment Leads to the Formation of Norfloxacin-Resistant Isolates with Mutations in gyrA, gyrB, or the acrAB Promoter (PacrAB) and Kanamycin-Resistant Isolates with Mutations in rpsL or arcA (A and B) Isolates with point mutation resulting in a D82G or D87Y substitution in GyrA (A) or a S464F substitution in GyrB (B). (C) T-to-A DNA base pair mutation in the AcrR/EnvR binding site of the −35 region of PacrAB. PacrAB is partially annotated to show the −10 and −35 regions (bold), the transcription start site (capitalized A), and the AcrR/EnvR binding site (underlined). (D) Isolates with insertion between base pair 92 and 93 (K58) and between base pair 78 and 79 (K62) resulting in truncation of RpsL. (E) Isolate with a single base pair insertion between base pair 211 and 212 resulting in a truncated ArcA protein missing the majority of the helix-turn-helix (HTH) DNA binding domain. See also Table S1. Molecular Cell 2010 37, 311-320DOI: (10.1016/j.molcel.2010.01.003) Copyright © 2010 Elsevier Inc. Terms and Conditions