title: Subinhibitory quinupristin/dalfopristin attenuates virulence of Staphylococcus aureus.
abstract: OBJECTIVE
  The semi-synthetic streptogramin quinupristin/dalfopristin antibiotic exerts potent bactericidal activity against Staphylococcus aureus. We investigated whether, like other bactericidal antibiotics used at subinhibitory concentrations, quinupristin/dalfopristin enhances release of toxins by Gram-positive cocci.
  
  
  METHODS
  The activity of quinupristin/dalfopristin on exotoxin release by S. aureus was investigated by 2D SDS-PAGE combined with MALDI-TOF/MS analysis and by western blotting.
  
  
  RESULTS
  We show that quinupristin/dalfopristin at subinhibitory concentrations reduces the release of S. aureus factors that induce tumour necrosis factor secretion in macrophages. Furthermore, quinupristin/dalfopristin but not linezolid attenuated S. aureus-mediated killing of infected host cells. When added to S. aureus cultures at different stages of bacterial growth, quinupristin/dalfopristin reduced in a dose-dependent manner the release of specific virulence factors (e.g. autolysin, protein A, alpha- and beta-haemolysins, lipases). In contrast, other presumably non-toxic exoproteins remained unchanged.
  
  
  CONCLUSIONS
  The results of the present study suggest that subinhibitory quinupristin/dalfopristin inhibits virulence factor release by S. aureus, which might be especially helpful for the treatment of S. aureus infections, where both bactericidal as well as anti-toxin activity may be advantageous.
authors.affiliation: Institute for Medical Microbiology, Immunology and Hygiene, Medical Center, University of Cologne, Goldenfelsstrasse, Köln, Germany.
authors.forename: Carmen
authors.initials: C
authors.lastname: Koszczol
authors.forename: Katussevani
authors.initials: K
authors.lastname: Bernardo
authors.forename: Martin
authors.initials: M
authors.lastname: Krönke
authors.forename: Oleg
authors.initials: O
authors.lastname: Krut
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005098:Exotoxins / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000382:microbiology; D051379:Mice; D008826:Microbial Sensitivity Tests; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013211:Staphylococcus aureus / Q000187:drug effects / Q000378:metabolism / Q000472:pathogenicity*; D014769:Virginiamycin / Q000494:pharmacology*; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D005098:Exotoxins; D037521:Virulence Factors; D014769:Virginiamycin; C062940:quinupristin-dalfopristin