Plasma-activated liquid as a potential decontaminant in healthcare: assessment of antibacterial activity and use with cleaning cloths

Abstract

Background: Cold air plasma (CAP) can generate plasma-activated liquids (PALs) with high concentrations of reactive oxygen (ROS) and nitrogen species (RNS), e.g., nitrites, with antimicrobial properties.

Aim: We investigated the concentrations of ROS and RNS in saline PAL. We assessed planktonic bacterial inactivation by PAL and the decontamination of contaminated cleaning cloths.

Methods: Phosphate-buffered saline (PBS) was treated with an air-driven CAP jet for 90 or 300 s to generate PAL. The ROS and RNS were measured using quantitative fluorescent (2,7-dichlorofluorescin diacetate) and colourimetric (Greiss) assays. Isolates of MRSA and Escherichia coli were incubated in PAL overnight and inactivation measured through colony forming unit (cfu) assays. Sections of cleaning cloths were incubated with MRSA and E. coli, and treated with PAL for 1 h. Bacterial inactivation was measured through resazurin reduction assays.

Results: Nitrites increased from 0.1 μM in untreated PBS to 49.1 μM and to 94.0 μM in 90- and 300-s CAP-treated PAL, respectively. ROS increased from 30 μM in untreated PBS to 75 μM and to 103 μM in 90- and 300-s CAP-treated PAL, respectively. 90-s PAL reduced MRSA and E. coli viability (P<0.05) and 300-s PAL resulted in more than a 7-log reduction of both. One-hour treatment of contaminated cleaning cloths in PAL resulted in a 55% and 73% reduction in viable MRSA and E. coli, respectively (P<0.05).

Conclusion: Inactivation of planktonic bacteria correlated with ROS and RNS concentrations. PAL reduced bacteria contaminated cleaning cloths. PAL has potential as a hospital disinfectant, including cleaning cloths.

Keywords: Cold plasma; Decontamination; Disinfection; E. coli; MRSA.