Plasma inactivation of microbial biofilms

The aim of this project is to investigate the inactivation and protection mechanisms of spores and biofilms treated by low-pressure plasmas (LPP) and cold atmospheric pressure plasmas (CAP). Approximately 80 % of human bacterial infections involve biofilm-associated organisms yielding common diseases like dental caries but also chronic wounds, urinary tract and lung infections. Especially in the case of patients with indwelling devices (e.g., catheters, stents, implants), infections acquired during hospital stays (nosocomial infections, NI) are often associated with biofilms.

To evaluate the applicability of LPPs and CAPs for biofilm inactivation, the sterilization mechanisms and efficiency of a Dielectric Barrier Discharge (DBD) will be compared to those of an Inductively Coupled Plasma (ICP). To do this, methods are also established to produce highly reproducible biofilms in different growth conditions. As a result, the inactivation and protection mechanisms of biofilms under treatment by LPPs and CAPs can be studied using biofilms in different growth stages and biofilm mutants lacking different parts of the complex biofilm structure as well as DNA-repair mechanisms.

To connect the survival experiments, both plasma sources will be characterized regarding their photon emission in the VUV and UV as well as their chemical composition and resulting radical fluxes towards the biological samples.

The focus of the work at RUB will be on the characterization of the plasma sources and the evaluation of bacillus subtilis spore experiments. This work is supported by our project partners from the DLR (Deutsches Zentrum für Luft- und Raumfahrt, Aerospace Microbiology Research Group lead by Prof. Dr. Ralf Möller). By combining the results of plasma and biological characterization, insights into the protection and inactivation mechanisms from single spores to fully developed biofilms can be achieved.