Insects as models to study burn wound infection and wound microbiome

Abstract

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonBurns are one of the most common and morbid of injury types. It leads to a multitude of complications, of which burn wound infection is the leading cause of mortality among burn patients. Due to the complexity of burn wound trauma and infection it cannot be accurately studied in vitro. Currently available animal models are costly, high maintenance and strictly ethically regulated. We developed an insect-based burn wound model using wax moth, Galleria mellonella has recently been established. It follows many of the hallmarks of burn wound trauma seen in humans and mammalian models, such as increase in survival after the administration of fluid resuscitation which involves giving the patient intravenous fluids to restore the fluid loss during the burn wound injury, increase in mortality with the increase of the burn surface area and a decrease in survival after a topical burn infection. This model is affordable, easy to maintain and handle and has no ethical regulation associated with it. The G. mellonella burn wound model has a potential to reduce and replace the use of mice in burn research. In this work, we established the G. mellonella burn wound model as a model for high throughput screening of probiotic bacteria. We showcase that application of both colonies and supernatant of Lactobacillus spp increases the survival in the G. mellonella burn wound model. Furthermore, we show that this model is capable of distinguishing between more and less therapeutically effective strains. The therapeutic efficacy was determined by comparing the effect of the treatment the wound with the probiotic bacteria on the survival of the wound infection in the G. mellonella. Additionally, we characterise a new burn wound probiotic C. acnes using this model and propose the carbon source competition as a potential strategy to modulate and treat wound infections by showcasing the importance of the glucose availability effect on the virulence of P. aeruginosa PA14 infection in the G. mellonella burn wound infection model. Lastly, we characterise the transcriptomic response of P. aeruginosa PA14 and A. baumannii AB5075 in the G. mellonella burn wound infection model and in the G. mellonella injection model, showcasing multiple overlaps of this model with other animal models and the transcriptomic response observed in human associated models and clinical isolates. The findings presented in this work not only further develop the G. mellonella burn wound model and establish it as a valid tool for high-throughput screening of burn wound probiotic treatments but also advance our understanding of the host-pathogen interactions in the burn wound infections which provides an alternative route to infection management. Furthermore, this research using G. mellonella will facilitate further replacement of the use of higher animals in research as well as facilitating more efficient mining for novel burn wound treatments