Eradication and phenotypic tolerance of Burkholderia cenocepacia biofilms exposed to atmospheric pressure non-thermal plasma

• Non-thermal plasma is an effective tool for rapid eradication of biofilms of clinical isolates of Burkholderia cenocepacia.
• B. cenocepacia biofilms exhibit significant variability in susceptibility to plasma exposure.
• In this study, susceptibility to plasma exposure was shown to correlate with biomass production in biofilms and catalase production in planktonic cultures.
• Knowledge of the mechanism by which the bactericidal activity of non-thermal plasma may be attenuated, provides important information for the design and optimisation of non-thermal plasma sources for infection control.
• Susceptibility to plasma exposure correlates to biomass in biofilms and catalase production in planktonic cultures.
• Bactericidal activity of non-thermal plasma is attenuated by biofilm components.

Chronic lung infection with bacteria from the Burkholderia cepacia complex (BCC), and in particular B. cenocepacia, is associated with significant morbidity and mortality in patients with cystic fibrosis (CF). B. cenocepacia can spread from person to person and exhibits intrinsic broad-spectrum antibiotic resistance. Recently, atmospheric pressure non-thermal plasmas (APNTPs) have gained increasing attention as a novel approach to the prevention and treatment of a variety of hospital-acquired infections. In this study, we evaluated an in-house-designed kHz-driven plasma source for the treatment of biofilms of a number of clinical CF B. cenocepacia isolates. The results demonstrated that APNTP is an effective and efficient tool for the eradication of B. cenocepacia biofilms but that efficacy is highly variable across different isolates. Determination of phenotypic differences between isolates in an attempt to understand variability in plasma tolerance revealed that isolates which are highly tolerant to APNTP typically produce biofilms of greater biomass than their more sensitive counterparts. This indicates a potential role for biofilm matrix components in biofilm tolerance to APNTP exposure. Furthermore, significant isolate-dependent differences in catalase activity in planktonic bacteria positively correlated with phenotypic resistance to APNTP by isolates grown in biofilms.