Development of a chronic wound in a diabetic (db/db) mouse by infection with biofilm

Abstract

Chronic wounds such as diabetic ulcers, pressure sores, and venous stasis ulcers are a major source of morbidity and mortality. Since chronic ulcers are not homogeneous, systematic study of ulcer therapies is difficult. Our goal is to create a standard chronic wound model. It has been shown that specialized microbial colonies known as biofilm are present in chronic human wounds. The microorganisms present in biofilm are protected from the host defenses, topical antiseptics, and systemic antibiotics. For this reason, biofilm infections persist and may contribute to poor wound healing. We hypothesize that application of biofilm to an already characterized diabetic mouse wound model may create a reproducible chronic wound. Bacterial biofilm was developed by incubating planktonic Pseudomonas aeruginosa (PAO-1) and transferring to polycarbonate membrane filters placed on LB agar plates. The biofilm (~10^8 CFU) was transferred to 6mm wounds created on the dorsal skin of diabetic mice and the wounds were covered with Tegaderm® dressing. The biofilm was transferred to the wounds at several different time points following wounding. The mice died if the biofilm was transferred soon after wounding; however, mice that were allowed to recover from the surgery before biofilm inoculation developed a purulent wound that persisted for weeks. In addition, the timing of Tegaderm® application proved to be a critical variable for purulence and quality of the wound. Ultimately, the development of a reproducible chronic wound in a diabetic mouse will allow in vivo testing of potential wound healing therapies.