A rat model of polymicrobial infection in full-thickness excision wounds

A reproducible animal model is required to study the pathophysiology of wound infections and for development of effective therapeutic interventions. The objective of this study was to produce an infected skin wound model utilizing the cecal microbiota in non-immunocompromised rats.

An excision wound was created on the dorsal surface of rats and inoculated with different concentration of cecal slurry (CS). Wound progression was investigated macroscopically by wound scoring and imaging. The rats were sacrificed on day 6 and microbial load, myeloperoxidase activity, histopathology, and scanning electron microscopy (SEM) were performed in wound tissue.

Inoculation of CS into excision wounds caused significantly (p < 0.05) delayed wound healing in comparison to non-infected wounds as revealed by slow wound closure (9.1 to 12.83%). A significant (p < 0.05) difference in wound score was observed between the infected and non-infected wounds. A significantly (p < 0.05) high microbial load (~10 ⁹ CFU/gm) was observed in infected wound which was supported by the presence of intensive bacterial colonization with sparse development of amorphous material on wound tissue during SEM analysis. A maximum increase of 1.76-fold in myeloperoxidase activity was observed in the infected wounds in comparison to non-infected wounds. Histopathology revealed increased amount of cellular infiltration, hematoma formation, and presence of bacterial aggregates in deep tissues.

The study reports a reproducible and relevant clinical model of wound infection where cecal microbiota was used as a source of infection. This model can provide a suitable platform for evaluation of new therapeutic interventions.