The dissolvable bead: A novel in vitro biofilm model for evaluating antimicrobial resistance

• Published in: Journal of microbiological methods 2017-11, Vol.142, p.46-51
• Main Authors: Dall, G.F., Tsang, S.T.J., Gwynne, P.J., Wilkinson, A.J., Simpson, A.H.R.W., Breusch, S.J.B., Gallagher, M.P.
• Format: Article
• Language: English
• Subjects: Alginates - chemistry; Anti-Bacterial Agents - pharmacology; Biofilms; Biofilms - drug effects; Biofilms - growth & development; Cryoelectron Microscopy; Drug Resistance, Bacterial - physiology; Enterococcus faecalis - growth & development; Enterococcus faecalis - isolation & purification; Escherichia coli - growth & development; Escherichia coli - isolation & purification; Gentamicins - pharmacology; Glucuronic Acid - chemistry; Hexuronic Acids - chemistry; Hospital-acquired infections; Humans; Klebsiella pneumoniae - growth & development; Klebsiella pneumoniae - isolation & purification; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Orthopaedic surgery; Periprosthetic joint infection; Pseudomonas aeruginosa - growth & development; Pseudomonas aeruginosa - isolation & purification; S. aureus; Staphylococcus aureus - growth & development; Staphylococcus aureus - isolation & purification; Streptococcus mutans - growth & development; Streptococcus mutans - isolation & purification
• ISSN: 0167-7012; 1872-8359
• DOI: 10.1016/j.mimet.2017.08.020

In vitro biofilm assays are a vital first step in the assessment of therapeutic effectiveness. Current biofilm models have been found to be limited by throughput, reproducibility, and cost. We present a novel in vitro biofilm model, utilising a sodium alginate substratum for surface biofilm colony formation, which can be readily dissolved for accurate evaluation of viable organisms. The dissolving bead biofilm assay was evaluated using a range of clinically relevant strains. The reproducibility and responsiveness of the assay to an antimicrobial challenge was assessed using standardised methods. Cryo-scanning electron microscopy was used to image biofilm colonies. Biofilms were grown for 20h prior to testing. The model provides a reproducible and responsive assay to clinically-relevant antimicrobial challenges, as defined by established guidelines. Moreover cryo-scanning electron microscopy demonstrates that biofilm formation is localised exclusively to the alginate bead surface. Our results suggest that this simple model provides a robust and adaptable assay for the investigation of bacterial biofilms. •We present a novel in vitro biofilm model, utilising a sodium alginate substratum.•It generates reproducible staphylococcal and non-staphylococcal biofilms.•It reliably quantifies biofilm eradication, as measured by reduction in cell counts.