The impact of simultaneous inoculation of Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans on rodent burn wounds

Burn wound infection often involves a diverse combination of bacterial and fungal pathogens. In this study, we characterize the mixed species burn wound infection by inoculating the burn surface with 1 x 10(3/4/5) CFU of Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans in a 1:1:1 ratio. Using the revised Walker-Mason scald burn rat model, 168 male Sprague-Dawley rats (350-450 g) subject to similar to 10% TBSA burn injury, with or without inoculation, were evaluated for 11 days after burn. In the wound, P. aeruginosa and S. aureus formed robust biofilms as determined by the bacterial tissue load, similar to 1 x 10(9) CFU/g, and expression of key biofilm genes. Interestingly, within 3 days C. albicans achieved tissue loads of similar to 1 x 10(6) CFU/g, but its numbers were significantly reduced beyond the limit of detection in the burn wound by day 7 in partial-thickness injuries and by day 11 in full-thickness injuries. The pathogenic biofilms contributed to burn depth progression, increased release of HMGB-1 into circulation from injured tissue, and significantly elevated the numbers of circulating innate immune cells (Neutrophils, Monocytes, and Basophils). This robust model of multispecies burn wound infection will serve as the basis for the development of new antimicrobials for combating biofilm-based wound infections. Published by Elsevier Ltd.

Automated summary

This study characterized mixed species burn wound infections by inoculating burn surfaces with Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans. The presence of biofilms from these pathogens in the wound led to burn depth progression, increased release of inflammatory mediators, and elevated circulating immune cells. The findings provide insights for developing new antimicrobials targeting biofilm-based wound infections.