An in vitro model for the growth and analysis of chronic wound MRSA biofilms

Aims: To develop an in vitro model (Colony/drip-flow reactor - C/DFR) for the growth and analysis of methicillin-resistant Staphylococcus aureus (MRSA) biofilms.

Methods and results: Using the C/DFR model, biofilms were grown on the top of polycarbonate filter membranes inoculated with a clinical isolate of MRSA, placed on absorbent pads in the DFR and harvested after 72 h. The biofilms varied from 256 to 308 μm in thickness with a repeatability standard deviation of 0·22. Testing of antimicrobial agents was also performed where C/DFR biofilms were grown in parallel with conventional colony biofilms. A saline solution (control), 1% silver sulfadiazine solution, and 0·25% Dakin's solution were used to treat the biofilms for 15 min. Microscopic evaluation of biofilm morphology and thickness was conducted. The Dakins solution in both models produced statistically significantly higher log reductions than silver sulfadiazine treatment.

Conclusions: The C/DFR biofilms were thick and repeatable and exhibited higher resistance to Dakins solution than the treated colony biofilms.

Significance and impact of the study: The C/DFR can be used as a tool for examining complex biofilm physiology as well as for performing comparative experiments that test wound care products and novel antimicrobials.