title: Mutational Consequences of Ciprofloxacin in Escherichia coli.
abstract: We examined the mutagenic specificity of the widely used antibiotic ciprofloxacin (CPR), which displays weak to moderate mutagenic activity in several bacteria and generates short in-frame deletions in rpoB in Staphylococcus aureus To determine the spectrum of mutations in a system where any gene knockout would result in a recovered mutant, including frameshifts and both short and long deletions, we examined CPR-induced mutations in the thymidylate synthase-encoding thyA gene. Here, any mutation resulting in loss of thymidylate synthase activity generates trimethoprim (Trm) resistance. We found that deletions and insertions in all three reading frames predominated in the spectrum. They tend to be short deletions and cluster in two regions, one being a GC-rich region with potential extensive secondary structures. We also exploited the well-characterized rpoB-Rif(r) system in Escherichia coli to determine that cells grown in the presence of sublethal doses of CPR not only induced short in-frame deletions in rpoB, but also generated base substitution mutations resulting from induction of the SOS system. Some of the specific point mutations prominent in the spectrum of a strain that overproduces the dinB-encoded Pol IV were also present after growth in CPR. However, these mutations disappeared in CPR-treated dinB mutants, whereas the deletions remained. Moreover, CPR-induced deletions also occurred in a strain lacking all three SOS-induced polymerases. We discuss the implications of these findings for the consequences of overuse of CPR and other antibiotics.
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, and David Geffen School of Medicine, University of California, Los Angeles, California, USA.
authors.forename: Lisa Yun
authors.initials: LY
authors.lastname: Song
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, and David Geffen School of Medicine, University of California, Los Angeles, California, USA.
authors.forename: Marisa
authors.initials: M
authors.lastname: Goff
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, and David Geffen School of Medicine, University of California, Los Angeles, California, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Davidian
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, and David Geffen School of Medicine, University of California, Los Angeles, California, USA.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Mao
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, and David Geffen School of Medicine, University of California, Los Angeles, California, USA.
authors.forename: Marisa
authors.initials: M
authors.lastname: London
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, and David Geffen School of Medicine, University of California, Los Angeles, California, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Lam
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, and David Geffen School of Medicine, University of California, Los Angeles, California, USA.
authors.forename: Madeline
authors.initials: M
authors.lastname: Yung
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, and David Geffen School of Medicine, University of California, Los Angeles, California, USA jhmiller@microbio.ucla.edu.
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Miller
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics; D009154:Mutation; D059645:Mutation Rate; D013014:SOS Response, Genetics / Q000187:drug effects / Q000235:genetics; D017384:Sequence Deletion
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; C540081:rpoB protein, E coli; D002939:Ciprofloxacin; D012321:DNA-Directed RNA Polymerases