Avaliação de um modelo de ferida cutânea com biofilme de Pseudomonas aeruginosa em camundongos

Abstract

Título: Evaluation of a model of skin wound with Pseudomonas aeruginosa biofilm in mice Introduction: the complexity of bacterial biofilms and the limitations of handling them in clinical practice require the development of experimental models to study the behavior of these entities in living tissues that can support the management of these microorganisms in clinical practice. From this perspective, the experimental model involving skin wounds with Pseudomonas aeruginosa biofilm is an important tool to identify the biofilm and to evaluate new therapeutic possibilities for the chronic wound healing process. Objective: to evaluate an experimental model of excisional cutaneous wounds with Pseudomonas aeruginosa biofilm in mice. Material and method: this is a preclinical study of a quantitative and translational nature. Healthy C57BL/6 mice aged 8-12 weeks and weighing 20-30g were used. The animals were randomly assigned to two groups denominated as control (Pbs) and intervention (Pa). The biofilm formation and induction profile were evaluated by means of the wound closure kinetics, the quantitative culture of the wounds and liver, the quantification of leukocytes in the peripheral blood, and via wound evaluation using transmission electron microscopy (TEM). Statistical analyses were performed using the GraphPad Prism software, version 6.0, and the results were expressed as the mean ± standard error of the mean. Values of p<0.05 were considered significant. Results: the bacterial load safe for inducing infection with P. aeruginosa and for animal survival was 10*4 CFU/mL. The evaluation of the closing kinetics and of the area of the wounds showed that, at 5 and 7 days, the animals of the Pa group had a statistically significant delay in the healing process when compared to the Pbs group. Macroscopically, it was noted that the wounds of the Pa group were covered, partially or in whole, by necrotic tissue with a yellow, moist, and thick aspect until the 10th day of the experiments. There was a greater weight variation in Pa group animals compared to the Pbs group, being statistically significant at 5 days. The differences noted in the wound culture at 5 and 7 days and the differential quantification of basophils at 3 days were statistically significant. The differences seen in the liver culture, in the global and differential quantification of other leukocytes (neutrophils, eosinophils, lymphocytes, and monocytes), were not significant in this study. In the evaluation of the wounds via TEM, it was not possible to identify the presence of bacteria in the planktonic form or biofilm form. Conclusion: the bacterial load used to induce infection in the wounds was safe to ensure animal survival and wound colonization, as confirmed by the delay in the healing process and the absence of systemic infection in the animals in the intervention group. However, the evaluation using TEM did not detect the presence of the biofilm or of the Pseudomonas in the planktonic form in the investigated wounds. This demonstrates the need for adjustments in the technique that was used for TEM to ensure the identification of the biofilm to validate the proposed infected wound model.