A new device for rapid evaluation of antibiofilm formation
Résumé
Objectives: This study describes the implementation of a new assay: Biofilm Ring Test ® to evaluate the efficacy of decontamination solutions to inhibit biofilm formation. This method is based on the immobilization of magnetic microbeads by bacterial cells forming biofilm in a modified polystyrene microtiter plate. Proteinase K (PK) was used as biofilm inhibitor in two models of biofilm formation in anaerobic conditions; Porphyromonas gingivalis ATCC 33277 mono specie and P. gingivalis/Streptococcus gordonii DL1 bi-species biofilms. Methods: Two hundred µl from P. gingivalis or P. gingivalis/S. gordonii culture were loaded in each well in triplicate. The PK solution was applied directly at a final concentration of 0.2%. After incubation at 37°C in an anaerobic incubator, plates were scanned prior and after magnetization and a BioFilm Index (BFI) was measured with the Biofilm Control®Software. A BFI ≤ 2 means a full immobilization of beads by a completely formed biofilm whereas a BFI ≥12 indicates no biofilm formation. Results: The capacity of different bacterial strains to form biofilm was validated using BioFilm Ring Test®. The BFI reached a value of 1.5 after 7 h for P. gingivalis alone and 3 h for the mixture of strains. Under the same conditions, the BFI increased when the 0.2% PK solution was added and reached a value of 4.70 ± 0.2 and 9.40 ± 0.1 respectively. The increased BFI compared to those observed in the absence of biofilm inhibitor showed the capacity of this new device to evaluate bacterial biofilm formation. Conclusion: In comparison with laborious methods, the Biofilm Ring Test ® may be used as a rapid, reproducible and easy-handling device to determine the effectiveness of anti-biofilm molecules. Considering these properties, this assay can be implemented for screening of biofilm formation by high numbers of bacterial strains with various molecules in the same assay.