Evaluation of Antimicrobial Agents Against Biofilms Grown in the Drip Flow Bioreactor Using Different Models

Background: Biofilms are formed when microbial cells adhere to a surface, and each other, and secrete extracellular polymeric substance (EPS), encasing themselves in a matrix. Biofilms can form on abiotic and biotic surfaces, such as medical devices and wounds causing infection and delayed wound healing.

Purpose: The aim of this study was to set up several in vitro models, representative of different surfaces, using the drip flow bioreactor and to evaluate several antimicrobial agents to treat the biofilm.

Methods: Three models were developed using 3 different surfaces and immature (24 H) and mature (48 H) biofilms of Pseudomonas aeruginosa. The first model was set up in accordance with ASTM E2647-13. This involved growing a biofilm for 48 H on a glass coupon. The second model was set up using adsorbent pads and membrane filters. The third model utilised pig skin. Treatment was applied for 24 H before neutralizing and either scraping or sonicating the samples. Biofilm density was determined by performing serial dilutions and plating onto agar.

Results: The models employed here all showed good P. aeruginosa biofilm growth, with cell density of 1 x 10(8) CFU/mL. Treatment with antimicrobial agents, showed varying results depending on the model employed.

Conclusion: The in vitro models set up here can be used to evaluate efficacy of antimicrobial based wound dressings against biofilms formed on different surfaces.