Development of a murine model of biofilm-infected diabetic pressure ulcers
Abstract
The purpose of this study was to develop an animal model of biofilm-infected diabetic pressure ulcers for use in wound pathophysiology and treatment studies. The wounding techniques and mouse strain were determined by the results of initial pilot testing. Twelve-week-old, male, TALLYHO/JngJ mice (n=10) were selected for their similarity to type II diabetes mellitus in humans. Hyperglycemia was confirmed and neodymium rare earth magnets were placed on either side of a dorsal skin fold to create two identical pressure wounds on each mouse. One wound was inoculated with a Staphylococcus aureus/Pseudomonas aeruginosa mixture (106 CFU/0.1 mL); the other was used as a control. Wound surface area was measured and recorded using a point-of-care digital wound measurement device. The wounds were harvested when one wound had healed or at day 22, whichever came sooner. Samples were evaluated histologically (H&E and Gram stains) and bacterial characterization was performed using pyrosequencing. Wound area was compared over time between inoculated and control sides. Significance was set at p≤0.05. Similar sized wounds were created in all 10 mice. There was a significant difference in inoculated versus control wounds (p<0.0001), time since wounding (p<0.0001), and interaction between the two variables (p=0.0032) in wound surface area. The surface area for inoculated wounds was larger than the control wounds on days 5 (p=0.0044), 7 (p=0.0012), 10 (p<0.0001), 12 (p=0.0014), and 16 (p=0.0499). All control (9/9) and 6/9 inoculated wounds healed by the time of explant. Four of the control and 5/6 of the healed inoculated wounds showed histologic evidence of chronic active inflammation. Biofilm was identified in histologic sections from one inoculated wound harvested on day 7 and in the three open inoculated wounds harvested at the end of the study. Bacteria identified within the wounds included S. aureus and P. aeruginosa, in addition to multiple other aerobic and anaerobic species, the most common of which were Staphylococcus lugdunensis, Bacilis subtilis, Leptospira broomii, and Escherichia coli. Pressure ulcers inoculated with bacteria known to produce a biofilm were larger and took longer to heal than control wounds in this diabetic mouse model. While initial results are promising, additional study is needed to further characterize this model.
Degree
M.S.
Advisors
Freeman, Purdue University.
Subject Area
Medicine|Surgery|Veterinary services
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