title: Comparison of biofilm formation between major clonal lineages of methicillin resistant Staphylococcus aureus.
abstract: OBJECTIVE
  Epidemic methicillin-resistant S. aureus (MRSA) clones cause infections in both hospital and community settings. As a biofilm phenotype further facilitates evasion of the host immune system and antibiotics, we compared the biofilm-forming capacities of various MRSA clones.
  
  
  METHODS
  Seventy-six MRSA classified into 13 clones (USA300, EMRSA-15, Hungarian/Brazilian etc.), and isolated from infections or from carriers were studied for biofilm formation under static and dynamic conditions. Static biofilms in microtitre plates were quantified colorimetrically. Dynamic biofilms (Bioflux 200, Fluxion, USA) were studied by confocal laser-scanning and time-lapse microscopy, and the total volume occupied by live/dead bacteria quantified by Volocity 5.4.1 (Improvision, UK).
  
  
  RESULTS
  MRSA harbouring SCCmec IV produced significantly more biomass under static conditions than SCCmec I-III (P = 0.003), and those harbouring SCCmec II significantly less than those harbouring SCCmec I or III (P<0.001). In the dynamic model, SCCmec I-III harbouring MRSA were significantly better biofilm formers than SCCmec IV (P = 0.036). Only 16 strains successfully formed biofilms under both conditions, of which 13 harboured SCCmec IV and included all tested USA300 strains (n = 3). However, USA300 demonstrated remarkably lower percentages of cell-occupied space (6.6%) compared to the other clones (EMRSA-15 = 19.0%) under dynamic conditions. Time-lapse microscopy of dynamic biofilms demonstrated that USA300 formed long viscoelastic tethers that stretched far from the point of attachment, while EMRSA-15 consisted of micro-colonies attached densely to the surface.
  
  
  CONCLUSIONS
  MRSA harbouring SCCmec types IV and I-III demonstrate distinct biofilm forming capacities, possibly owing to their adaptation to the community and hospital settings, respectively. USA300 demonstrated abundant biofilm formation under both conditions, which probably confers a competitive advantage, contributing to its remarkable success as a pathogen.
authors.affiliation: Department of Medical Microbiology, University of Antwerp, Antwerp, Belgium; Vaccine & Infectious Disease Institute, University of Antwerp, Antwerp, Belgium.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Vanhommerig
authors.affiliation: Department of Medical Microbiology, University of Antwerp, Antwerp, Belgium; Vaccine & Infectious Disease Institute, University of Antwerp, Antwerp, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Moons
authors.affiliation: Molecular pathology Group, Cell Biology and Histology, University of Antwerp, Antwerp, Belgium; Department of Research Methodology, University of Medicine and Pharmacy of Craiova, Craiova, Romania.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pirici
authors.affiliation: Department of Medical Microbiology, University of Antwerp, Antwerp, Belgium; Vaccine & Infectious Disease Institute, University of Antwerp, Antwerp, Belgium.
authors.forename: Christine
authors.initials: C
authors.lastname: Lammens
authors.affiliation: Viral Genetics Research Group, Vrije Universiteit Brussel, Brussels, Belgium.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Hernalsteens
authors.affiliation: Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium; Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium.
authors.forename: Henri
authors.initials: H
authors.lastname: De Greve
authors.affiliation: Vaccine & Infectious Disease Institute, University of Antwerp, Antwerp, Belgium; Molecular pathology Group, Cell Biology and Histology, University of Antwerp, Antwerp, Belgium.
authors.forename: Samir
authors.initials: S
authors.lastname: Kumar-Singh
authors.affiliation: Department of Medical Microbiology, University of Antwerp, Antwerp, Belgium; Vaccine & Infectious Disease Institute, University of Antwerp, Antwerp, Belgium.
authors.forename: Herman
authors.initials: H
authors.lastname: Goossens
authors.affiliation: Department of Medical Microbiology, University of Antwerp, Antwerp, Belgium; Vaccine & Infectious Disease Institute, University of Antwerp, Antwerp, Belgium.
authors.forename: Surbhi
authors.initials: S
authors.lastname: Malhotra-Kumar
mesh_terms: D018441:Biofilms / Q000254:growth & development; D018533:Biomass; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D050296:Microbial Viability; D013203:Staphylococcal Infections / Q000175:diagnosis / Q000382:microbiology*
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