A simple in vitro model to test the efficacy of antimicrobial agents released from dressings

A new model for in vitro evaluation of an activity of antibacterial agents released from delivery systems containing antibiotics or antiseptics was developed. The model was composed of two layers of agar gel of two different concentrations in PBS. In the upper gel, the wells were cut and filled with polyurethane sponges saturated with bacterial broth culture. The sponges were then covered with tested dressings containing antibacterial agent. The model was tested by using two bacterial strains, Pseudomonas aeruginosa or Staphylococcus aureus and experimental collagen dressing with doxycyclin, amikacin, or with silver sulfadiazine. The number of colony-forming units (CFU) in the polyurethane sponges was significantly lower under the dressings with antibacterial agents as compared to the control (the same dressing without antimicrobials) during 3 days of observation. The new in vitro model can be recommended for examination of different antibacterial delivery systems instead of experimentally infected wounds in laboratory animals or instead of the other in vitro models.