Now showing 1 - 5 of 5
  • Publication
    Rapid depletion of dissolved oxygen in 96 well microtitre plate Staphylococcus epidermidis biofilm assays promotes biofilm development and is influenced by inoculum cell concentration
    Biofilm-related research using 96-well microtiter plates involves static incubation of plates indiscriminate of environmental conditions, making oxygen availability an important variable which has not been considered to date. By directly measuring dissolved oxygen concentration over time we report here that dissolved oxygen is rapidly consumed in Staphylococcus epidermidis biofilm cultures grown in 96-well plates irrespective of the oxygen concentration in the gaseous environment in which the plates are incubated. These data indicate that depletion of dissolved oxygen during growth of bacterial biofilm cultures in 96-well plates may significantly influence biofilm production. Furthermore higher inoculum cell concentrations are associated with more rapid consumption of dissolved oxygen and higher levels of S. epidermidis biofilm production. Our data reveal that oxygen depletion during bacterial growth in 96-well plates may significantly influence biofilm production and should be considered in the interpretation of experimental data using this biofilm model.
      997Scopus© Citations 19
  • Publication
    Oxygen-mediated regulation of biofilm development is controlled by the alternative sigma factor sigma(B) in Staphylococcus epidermidis
    Using a modified rotating-disk reactor to sparge oxygen to Staphylococcus epidermidis cultures, we found that oxygen negatively regulates biofilm development by influencing the activity of {sigma}B. Under anaerobic conditions, increased {sigma}B activity activates icaADBC, which encodes enzymes responsible for polysaccharide intercellular adhesin synthesis, by repressing transcription of the negative regulator icaR.
      479Scopus© Citations 35
  • Publication
    Tailoring Nanoparticle-Biofilm Interactions to Increase the Efficacy of Antimicrobial Agents Against Staphylococcus aureus
    Background: Considering the timeline required for the development of novel antimicrobial drugs, increased attention should be given to repurposing old drugs and improving anti-microbial efficacy, particularly for chronic infections associated with biofilms. Methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) are common causes of biofilm-associated infections but produce different biofilm matrices.MSSA biofilm cells are typically embedded in an extracellular polysaccharide matrix, whereas MRSA biofilms comprise predominantly of surface proteins and extracellular DNA (eDNA). Nanoparticles (NPs) have the potential to enhance the delivery of antimicro-bial agents into biofilms. However, the mechanisms which influence the interactions between NPs and the biofilm matrix are not yet fully understood. Methods:To investigate the influence of NPs surface chemistry on vancomycin (VAN) encapsulation and NP entrapment in MRSA and MSSA biofilms, mesoporous silica nano-particles (MSNs) with different surface functionalization (bare-B, amine-D, carboxyl-C,aromatic-A) were synthesised using an adapted Stöber method. The antibacterial efficacy of VAN-loaded MSNs was assessed against MRSA and MSSA biofilms. Results: The two negatively charged MSNs (MSN-B and MSN-C) showed a higher VAN loading in comparison to the positively charged MSNs (MSN-D and MSN-A). Cellular binding with MSN suspensions (0.25 mg mL−1) correlated with the reduced viability of both MSSA andMRSA biofilm cells. This allowed the administration of low MSNs concentrations while maintaining a high local concentration of the antibiotic surrounding the bacterial cells. Conclusion: Our data suggest that by tailoring the surface functionalization of MSNs,enhanced bacterial cell targeting can be achieved, leading to a novel treatment strategy for biofilm infections.
      228Scopus© Citations 36
  • Publication
    Disinfection of meticillin-resistant Staphylococcus aureus and Staphylococcus epidermidis biofilms using a remote non-thermal gas plasma
    The effective disinfection of hospital surfaces is recognised as an important factor in preventing hospital-acquired infections. The purpose of this study was to quantify the disinfection rate of a novel gas plasma system on clinically relevant biofilms. Clinical isolates of Staphylococcus epidermidis and methicillin-resistant Staphylococcus aureus (MRSA) were grown as biofilms on glass surfaces and tested in a disinfection container remote from the plasma source. The strains used in this study were known to produce substantial quantities of biofilm and average log10 counts were 9.0 and 9.1 cfu/cm2 for S. epidermidis and MRSA respectively. Counts were reduced by between 4 and 4.5 log10 after 1 h of exposure for MRSA and S. epidermidis respectively. More prolonged treatment in the case of MRSA biofilms resulted in a 5.5 log10 reduction after 90 min. Biofilm samples were also placed in medical device packaging bags and similar rates of disinfection were observed.
      1704Scopus© Citations 48
  • Publication
    Characterisation of a modified rotating disk reactor for the cultivation of Staphylococcus epidermidis biofilm
    Aims:  The purpose of this study was to develop a system that would allow biofilms to be cultivated under strictly defined conditions in terms of dissolved oxygen, fluid shear and to assess whether the method was suitable for the detection of respiratory activity stratification in biofilm samples. Methods:  The system is a modified version a commercially available laboratory biofilm reactor and incorporates a number of features such as the provision of defined levels of dissolved oxygen, constant average shear, enhanced gas–liquid mass transfer, aseptic operation and the ability to remove biofilm for ex situ analysis during or after continuous cultivation. Conclusions:  The system was shown to be effective for the characterization of the effects of dissolved oxygen on a pure culture of Staphylococcus epidermidis. The versatility of the system offers the potential for cultivating pure culture biofilm in defined, controlled conditions and facilitates a range of analyses that can be performed ex situ. Significance and Impact of the Study:  The ability to provide strict regulation of environmental conditions and enhanced transfer of oxygen to the biofilm during cultivation are important, first because oxygen is known to regulate biofilm development in several micro-organisms and second because many conventional biofilm cultivation systems may not provide adequate oxygen supply to the biofilm.
      753Scopus© Citations 15