title: Alterations in the transcriptome and antibiotic susceptibility of Staphylococcus aureus grown in the presence of diclofenac.
abstract: BACKGROUND
  Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) which has been shown to increase the susceptibility of various bacteria to antimicrobials and demonstrated to have broad antimicrobial activity. This study describes transcriptome alterations in S. aureus strain COL grown with diclofenac and characterizes the effects of this NSAID on antibiotic susceptibility in laboratory, clinical and diclofenac reduced-susceptibility (DcRS) S. aureus strains.
  
  
  METHODS
  Transcriptional alterations in response to growth with diclofenac were measured using S. aureus gene expression microarrays and quantitative real-time PCR. Antimicrobial susceptibility was determined by agar diffusion MICs and gradient plate analysis. Ciprofloxacin accumulation was measured by fluorescence spectrophotometry.
  
  
  RESULTS
  Growth of S. aureus strain COL with 80 μg/ml (0.2 × MIC) of diclofenac resulted in the significant alteration by ≥2-fold of 458 genes. These represented genes encoding proteins for transport and binding, protein and DNA synthesis, and the cell envelope. Notable alterations included the strong down-regulation of antimicrobial efflux pumps including mepRAB and a putative emrAB/qacA-family pump. Diclofenac up-regulated sigB (σB), encoding an alternative sigma factor which has been shown to be important for antimicrobial resistance. Staphylococcus aureus microarray metadatabase (SAMMD) analysis further revealed that 46% of genes differentially-expressed with diclofenac are also σB-regulated. Diclofenac altered S. aureus susceptibility to multiple antibiotics in a strain-dependent manner. Susceptibility increased for ciprofloxacin, ofloxacin and norfloxacin, decreased for oxacillin and vancomycin, and did not change for tetracycline or chloramphenicol. Mutation to DcRS did not affect susceptibility to the above antibiotics. Reduced ciprofloxacin MICs with diclofenac in strain BB255, were not associated with increased drug accumulation.
  
  
  CONCLUSIONS
  The results of this study suggest that diclofenac influences antibiotic susceptibility in S. aureus, in part, by altering the expression of regulatory and structural genes associated with cell wall biosynthesis/turnover and transport.
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA. jtriordan@usf.edu
authors.forename: James T
authors.initials: JT
authors.lastname: Riordan
authors.forename: JoAnne M
authors.initials: JM
authors.lastname: Dupre
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Cantore-Matyi
authors.forename: Atul
authors.initials: A
authors.lastname: Kumar-Singh
authors.forename: Yang
authors.initials: Y
authors.lastname: Song
authors.forename: Shahrear
authors.initials: S
authors.lastname: Zaman
authors.forename: Sonia
authors.initials: S
authors.lastname: Horan
authors.forename: Nada S
authors.initials: NS
authors.lastname: Helal
authors.forename: Vijayaraj
authors.initials: V
authors.lastname: Nagarajan
authors.forename: Mohamed O
authors.initials: MO
authors.lastname: Elasri
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Wilkinson
authors.forename: John E
authors.initials: JE
authors.lastname: Gustafson
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004008:Diclofenac / Q000494:pharmacology*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D000894:Anti-Inflammatory Agents, Non-Steroidal; D001426:Bacterial Proteins; D004008:Diclofenac