Antimicrobial Effect on Bacteria in Biofilm and Planktonic state

Examensarbete för masterexamen

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Type: Examensarbete för masterexamen
Master Thesis
Title: Antimicrobial Effect on Bacteria in Biofilm and Planktonic state
Authors: Linse, Julia
Larsson, Anna
Abstract: The elimination of contaminating bacteria is essential in order to achieve proper wound healing. Bacteria can occur in two different states, as free-living (planktonic) cells or in aggregates adhered to a surface (biofilm). The bacteria behaves differently depending on in which state they occur and their differences and their sensitivity against Chlorhexidine digluconate have been of key interest during this thesis work. To investigate this, time-kill studies have been performed on the two common wound bacteria P. aeruginosa and S. aureus under static and dynamic conditions. The studies were performed on bacteria in both biofilm and in planktonic state. The minimum inhibitory concentration (MIC), the minimum biocidal concentration (MBC) and the minimum biofilm eradication concentration (MBEC) for the antimicrobial compound Chlorhexidine digluconate against the bacteria were used in time-kill studies under static and dynamic conditions. In the static time-kill studies the bacterial were treated with different concentrations of Chlorhexidine digluconate in the range from below the MIC to above the MBC. In the dynamic time-kill studies Chlorhexidine digluconate was added continuously to the bacteria to reach the determined MBC in different times. Results from the experiments showed that P. aeruginosa was less sensitive against treatment of Chlorhexidine digluconate than S. aureus was. There seemed to be persister cells within the P. aeruginosa population during all experiments since they managed to recover from antimicrobial treatment even if the bacterial concentration at a point was below the limit of detection. The experiments also showed that killing of P. aeruginosa seemed to be Cmax-driven, which means that a high concentration Chlorhexidine was needed to be delivered fast to the bacteria to achieve the best rate of killing. For S. aureus the killing seemed to be AUC-driven which means that a lower amount of the antimicrobial could be used but the bacteria needed to be exposed for a longer time. When the two bacterial species were in biofilm, both were less sensitive to Chlorhexidine digluconate and a higher concentration was needed in order to achieve the same rate of killing as for bacteria in planktonic state.
Keywords: Annan medicin och hälsovetenskap;Grundläggande vetenskaper;Hållbar utveckling;Innovation och entreprenörskap (nyttiggörande);Livsvetenskaper;Other Medical Sciences;Basic Sciences;Sustainable Development;Innovation & Entrepreneurship;Life Science
Issue Date: 2018
Publisher: Chalmers tekniska högskola / Institutionen för fysik (Chalmers)
Chalmers University of Technology / Department of Physics (Chalmers)
Collection:Examensarbeten för masterexamen // Master Theses

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