Development of in vitro wound infection model to study interactions between human dermal cells and biofilm bacteria

Examensarbete för masterexamen

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Type: Examensarbete för masterexamen
Master Thesis
Title: Development of in vitro wound infection model to study interactions between human dermal cells and biofilm bacteria
Authors: Allahyar, Ava
Abstract: Chronic wounds or so called hard to heal wounds are today a wide spread problem in the world and more effetive treatments are needed. Bacterial infection is a common reason for the impaired healing. Research during recent years has suggested that bacteria in wounds, as in nature, live in so called biofilms. These are bacterial aggregates encapsulated in a self-produced polymer matrix, a mode of growth that makes the bactera much less susceptible to antimicrobial agents and hos immune response. It is today hypothesized that bacterial biofilms may in fact be the major reason for the development of chronic wounds. The increasing bacterial resistance against antimicrobial agents and the lower sensitivity in bacteria living in biofilms need to be considered when developing new treatment strategies for infected wounds. Therefore, new and more complex in vitro models are needed for preclinical studies of candidate wound treatment products, simulating the environment in an infected wound. The aim of this thesis was to develop an in vitro model mimicking wound tissue containing human dermal fibroblasts in the presence of bacterial biofilm, formed by common wound pathogens. An additional aim was to evaluate the model by testing the impact on the system of the antimicrobial agent polyhexamethylene biguanide (PHMB). The wound pathogens used are Pseudomonas aeruginosa and Staphylococcus aureus. Both dermal cells and bacteria are cultured in collagen matrices byt physically separated from each other in a co-culture system. The effect of PHMB on bacteria and on fibroblasts was analyzed separately before the effect of the antibacterial substance was studied for the whole system. The evaluation of the effect of biofilm was performed by measuring fibroblast viability. A steady reduction of bacterial number was observed for the biofilm when treated with PHMB up to 400 ppm. How PHMB affects fibroblasts was harder to analyze as the substance in some way seems to disturb the viability measurement, although it is important to note that the substance does not seem to have a significant negative effect on the fibroblasts. Bacterial biofilms were then co-cultivated with the fibroblasts and it could be seen that the bacteria of the different strains have different effect on fibroblast viability. More fibroblasts seem to survive treatment with S.aureus biofilm compared to cells growing in the presence of P aeruginosa. When the co-culture is exposed to PHMB a higher survival of the fibroblasts can be observed. This was a first attempt to develop an in vitro model of an infected wound to use in the search for new treatment strategies. This study shows that a co-culture of dermal cells and bacteria is possible, although there are still many details to optimize before the model can be used for screening of antibacterial treatment.
Keywords: Industriell bioteknik;Industrial Biotechnology
Issue Date: 2010
Publisher: Chalmers tekniska högskola / Institutionen för kemi- och bioteknik
Chalmers University of Technology / Department of Chemical and Biological Engineering
Collection:Examensarbeten för masterexamen // Master Theses

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