title: Stimulation of Staphylococcus epidermidis growth and biofilm formation by catecholamine inotropes.
abstract: BACKGROUND
  Bacterial colonisation of indwelling medical devices by coagulase-negative staphylococci is a prevalent risk in intensive-care units. Factors determining biofilm formation and progression to catheter- related infection are incompletely understood. We postulated that administration of inotropic agents via indwelling intravenous catheters may stimulate growth and formation of biofilms by Staphylococcus epidermidis.
  
  
  METHODS
  Inocula representing physiologically relevant infecting doses of S epidermidis were incubated in a minimum medium supplemented with fresh human plasma in the presence or absence of pharmacological concentrations of norepinephrine or dobutamine. Biofilm formation on polystyrene and medical-grade silicone was examined. After incubation, cultures were assessed for growth and formation of biofilms by colony counting and scanning electronmicroscopy. The production of exopolysaccharide, a major constituent of S epidermidis biofilms, was also assessed by use of immunofluorescence microscopy.
  
  
  RESULTS
  Incubation of S epidermidis with catecholamine inotropes in the presence of human plasma resulted in a significant increase in growth compared with control on both polystyrene and silicone surfaces, with pronounced increases in biofilm formation as visualised by scanning electronmicroscopy. Experiments with transferrin labelled with radioactive iron showed the ability of catecholamine inotropes to facilitate acquisition of iron by S epidermidis. Immunofluorescence microscopy revealed extensive exopolysaccharide production associated with S epidermidis biofilms.
  
  
  CONCLUSIONS
  The ability of catecholamine inotropic drugs to stimulate bacterial proliferation and biofilm formation may be an aetiological factor in the development of intravascular catheter colonisation and catheter-related infection. The removal of iron from transferrin for subsequent use by S epidermidis is a possible mechanism by which catecholamine inotropes stimulate bacterial growth as biofilms.
authors.affiliation: Department of Surgery, Minneapolis Medical Research Foundation, Hennepin County Medical Center, Minneapolis 55404, USA. lytex001@umn.edu
authors.forename: Mark
authors.initials: M
authors.lastname: Lyte
authors.forename: Primrose P E
authors.initials: PP
authors.lastname: Freestone
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Neal
authors.forename: Barton A
authors.initials: BA
authors.lastname: Olson
authors.forename: Richard D
authors.initials: RD
authors.lastname: Haigh
authors.forename: Roger
authors.initials: R
authors.lastname: Bayston
authors.forename: Peter H
authors.initials: PH
authors.lastname: Williams
mesh_terms: D000328:Adult; D001422:Bacterial Adhesion; D018441:Biofilms / Q000254:growth & development*; D001769:Blood / Q000382:microbiology*; D004280:Dobutamine / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D009638:Norepinephrine / Q000494:pharmacology*; D011137:Polystyrenes; D012828:Silicones; D013212:Staphylococcus epidermidis / Q000502:physiology*
chemical_list: D011137:Polystyrenes; D012828:Silicones; D004280:Dobutamine; D009638:Norepinephrine