Validation of the Zürich burn-biofilm model
Section snippets
Background
Despite advances in the use of topical and parenteral antimicrobial therapy and the practice of early tangential burn-wound excision to reduce bacterial load, bacterial infection remains a major problem in the management of burn victims today. Critically ill thermally injured patients have a propensity to develop nosocomial infections for several reasons. Rates of ventilator-associated pneumonia, bloodstream infection and wound infection have all been shown to be higher than those for other
Bacteria used, preparation of inoculum
Enterococcus faecalis OMZ 422 (ATCC 29212), Escherichia coli OMZ 56 (ATCC 25922), Streptococcus intermedius OMZ 871 (SK57, ATCC 9895), Pseudomonas aeruginosa OMZ 154 (ATCC 27853) and Staphylococcus aureus OMZ 1122 (ATCC 25923) were obtained from the culture collection of the Institute of Oral Biology, University of Zürich. Strains were maintained by aerobic incubation at 37 °C for 36 h on plates of Columbia blood agar base (CBA, Oxoid, Basingstoke, Hamps., UK) supplemented with 5% (v/v)
Biofilm formation, growth and composition
The experimental set-up for biofilm formation is given in Fig. 1. The biofilms were formed in two steps, the 1st consisting of the establishment of a Gram-positive biofilm with S. aureus, S. intermedius and E. faecalis (0–41.5 h) and the 2nd bringing the addition and the establishment of the Gram-negatives P. aeruginosa and E. coli (41.5–64.5 h).
Aliquots of cell suspensions recovered from different biofilms and time points were examined for viability by fluorescence microscopy and were found to
Biofilm model mimicking the bacterial colonisation of burn wounds
The aim of our study was to establish and validate a burn-biofilm model, in particular in terms of repeatability. Whereas the clinical significance of bacterial biofilms has been increasingly recognised lately, our model represents, to the best of our knowledge, the first dedicated polyspecies burn-biofilm model. Based on methods developed in our laboratories in past years [11], [12], [13], [14], we have dubbed it ‘the Zürich burn-biofilm model’.
We have composed the polyspecies biofilm
Conclusions
Polyspecies burn-biofilm models are very important to study the efficiency of topical agents. These results should be more accurate in terms of use of these agents in vivo as compared with results obtained with planktonic cultures or monospecies biofilms. The Zürich burn-biofilm model represents a polyspecies-biofilm model that not only contains some of the most prevalent burn-wounds-associated Gram-positive and Gram-negative bacterial pathogens but also mimics the Gram-negative shift observed
Authors’ contributions
MG and BG designed the study, evaluated the data and wrote the article, TT performed the CLSM analyses, RG designed probes and edited the article, while PG provided editorial assistance. All authors read and approved the final manuscript.
Conflict of interest statement
The authors declare no conflicts of interest.
Acknowledgements
The authors are grateful to André Meier and Bärbel Sauer for excellent assistance in carrying out these biofilm experiments.
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