title: Salmonella Typhimurium exhibits fluoroquinolone resistance mediated by the accumulation of the antioxidant molecule H2S in a CysK-dependent manner.
abstract: To evaluate the contribution of cysK and cysM to the fluoroquinolone (ofloxacin) antibiotic resistance in Salmonella Typhimurium, and their impact on H2S and cysteine production through targeted mutagenesis.
  
  
  
  Salmonella Typhimurium 14028s and its cysK and cysM mutants were tested for their susceptibility to ofloxacin, as determined by a broth microdilution test (to determine the MIC) and survival curves. H2S levels were measured by the Pb(AC)2method and cysteine levels were determined using 5,5-dithio-bis-2-nitrobenzoic acid. DNA damage induced by antibiotic treatment was determined by PFGE. Finally, expression of cysK and cysM genes under antibiotic treatment was determined by real-time reverse transcription PCR.
  
  
  
  As determined by MIC, the ΔcysK strain was more resistant to ofloxacin, a reactive oxygen species (ROS)-producing fluoroquinolone, than the WT and ΔcysM strains, which correlates with survival curves. Moreover, the ΔcysK strain exhibited higher H2S levels and lower cysteine levels than the WT strain. Finally, the ΔcysK strain exhibited lower DNA damage upon challenge with ofloxacin than the WT and ΔcysM strains. These results are in accordance with lower expression of cysK under ofloxacin treatment in the WT strain.
  
  
  
  This work demonstrated that cysteine metabolism in Salmonella Typhimurium modulated H2S levels, conferring resistance to second-generation fluoroquinolones.
authors.affiliation: Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: J
authors.initials: J
authors.lastname: Frávega
authors.affiliation: Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: R
authors.initials: R
authors.lastname: Álvarez
authors.affiliation: Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: F
authors.initials: F
authors.lastname: Díaz
authors.affiliation: Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: O
authors.initials: O
authors.lastname: Inostroza
authors.affiliation: Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: C
authors.initials: C
authors.lastname: Tejías
authors.affiliation: Center for Integrative Medicine and Innovative Science, Facultad de Medicina, Universidad Andres Bello, Santiago, Chile.
authors.forename: P I
authors.initials: PI
authors.lastname: Rodas
authors.affiliation: Gut Microbiota and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.|Center for Bioinformatic and Integrative Biology, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: D
authors.initials: D
authors.lastname: Paredes-Sabja
authors.affiliation: Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: J A
authors.initials: JA
authors.lastname: Fuentes
authors.affiliation: Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: I L
authors.initials: IL
authors.lastname: Calderón
authors.affiliation: Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile fernandogil@unab.cl.
authors.forename: F
authors.initials: F
authors.lastname: Gil
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism*; D003547:Cysteine Synthase / Q000235:genetics / Q000378:metabolism*; D024881:Drug Resistance, Bacterial; D024841:Fluoroquinolones / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D006801:Humans; D006862:Hydrogen Sulfide / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D015242:Ofloxacin / Q000037:antagonists & inhibitors / Q000378:metabolism; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000502:physiology
chemical_list: D000900:Anti-Bacterial Agents; D000975:Antioxidants; D024841:Fluoroquinolones; D015242:Ofloxacin; D003547:Cysteine Synthase; D003545:Cysteine; D006862:Hydrogen Sulfide