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Comparison of biofilm formation between major clonal lineages of methicillin resistant Staphylococcus aureus.
Journal Contribution - Journal Article
Objectives: 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 biofilmforming
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.
As a biofilm phenotype further facilitates evasion of the host immune system and antibiotics, we compared the biofilmforming
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.
Journal: PLOS ONE
ISSN: 1932-6203
Volume: 9
Pages: 104561
Publication year:2014
Keywords:Staphylococcus aureus, MRSA, biofilm