Inactivation of Propionibacterium acnes and its biofilm by non-thermal plasma

• We used two devices, non-thermal soft plasma jet and non-thermal annular plasma jet.
• NSPJ showed inhibitory effect on Propionibacterium acnes with lower doses than NAPJ.
• Both devices showed inactivation for planktonic and biofilm states of P. acnes.
• In NSPJ, O, O2+, OH and N radicals while in NAPJ mainly OH were identified.
• Correlation is found between generated reactive species and bacterial inactivation.

Propionibacterium acnes (P. acnes) is an opportunistic gram positive pathogen which has become an important source of various surgical implant associated infections including artificial joints, shunts, heart valves and catheter's infections. In addition, P. acnes can form biofilm which may enhance the complications even more. Even though it is susceptible to most of the antibiotics but still hard to remove and in severe cases removal of device is suggested. This makes the failure of implants. These problems prompted us to find more efficient method to sterilize these contaminations. Non-thermal plasmas primarily generate reactive species and recently have emerged as an efficient tool for medical applications including sterilization. Therefore, in this study we evaluated the inactivation ability of two different plasma jets, non-thermal annular plasma jet (NAPJ) and non-thermal soft plasma jet (NSPJ) for P. acnes in planktonic state and biofilm state. And, we found that both plasma devices showed considerable inactivation potential in planktonic P. acnes and P. acnes biofilms. Especially, NSPJ showed better inhibitory effect in shorter exposer time than NAPJ which might be because of close exposure to plasma generated reactive species. Moreover, we found that intracellular and extracellular reactive species concentrations are correlated with plasma treatment time, which suggest their critical role in microbial inhibition.In conclusion, our study suggests that plasma technology may also be used to overcome the biofilm contamination problems associated with biomaterials including surgical devices.