M. R. GONZALEZ¹, B. FLEUCHOT¹, L. L. LAUCIELLO¹, P. JAFARI², L. A. APPLEGATE², W. RAFFOUL², Y.-A. QUE³, K. PERRON<sup>1

1</sup>Microbiology Unit, Dept. of Botany and Plant Biology, University of Geneva., ²Plastic, Reconstructive & Hand Surgery, Unit of Regenerative Therapy, UNIL/CHUV Lausanne, ³Service of Adult Intensive Care Medicine & Burns, CHUV Lausanne

BACKGROUND: Burn wound sepsis are currently the main cause of morbidity and mortality after severe burn injury. Bacterial pathogens such as Pseudomonas aeruginosa, Staphylococcus aureus and Acinetobacter baumanii impair patient recovery and lead to fatal issue. The specialized medical care required after burn injury faces major challenges to prevent bacterial development on the burn wounds. The Biological Biodegradable and anti-Bacterial Burn-wound Bandages (B5) platform, granted by Swiss TransMed, was created in order to improve the current biological dressing used to treat burn wound and to better understand the bacterial pathogenesis in a wound environment.

AIMS: Our specific research topics are i) the pathogenicity characterization of the major burn wound pathogen P. aeruginosa while growing in burn wound exudate and ii) the analysis of burn wound exudate composition in order to establish of an artificial burn wound medium.

RESULTS: We investigated the effect of burn wound exudates (BWE) on the virulence of those pathogens. BWE were collected within 7 days after burn trauma from 5 burn patients. We first monitored their effect on pathogen growth. In contrast to A. baumanii or S. aureus, P. aeruginosa was the only pathogen able to grow within these human fluids. Expression of typical virulence factors such as pyocyanin and pyoverdine were even enhanced compared to standard laboratory medium. An RNAseq analysis on P. aeruginosa growing in burn wound exudate was performed and is currently analyzed. A detailed chemical composition analysis of BWE was done, which enabled us to determine the major components of BWE and underline the metabolic modifications induced by burn trauma. These data are essential for the development of an artificial medium mimicking the burn wound environment and the establishment of an in vitro system to analyze the initial steps of burn wound infections.