Effects of cold atmospheric plasma (CAP) on bacteria and mucosa of the upper aerodigestive tract

Objective: Ear, nose and throat infections are among the most common reasons for absence from work. They are usually caused by various bacteria like Haemophilus influenzae, Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes. Cold atmospheric plasma (CAP) can effectively eliminate even multi-resistant bacteria and has no cytotoxic or mutagenic effects on the mucosa when applied for less than 60 s. Aim of the study was to evaluate the effects of CAP on common ENT bacteria and on the mucosa of the upper aerodigestive tract. Methods: The bactericidal effects of CAP against the bacteria most commonly causing ENT infections were investigated using the colony-forming units assay (CFU) on a Muller-Hinton agar plate after applying CAP for 30, 60, 90 and 120 s. To evaluate the interaction of CAP with mucosal cells, 3D mini organ cultures were treated for up to 180 s, after which cell viability and necrosis induction were evaluated. Results: Treatment with CAP for 60 s or longer induced at least a 3-log 10 reduction in the bacterial load (> 99.9%). Treatment times shorter than 60 s had only slight cytotoxic effects on cell viability and necrosis whereas treatment times above 60 s showed a fast increase of cytotoxic side effects. Conclusion: CAP exhibited strong bactericidal effects on the most common ENT pathogens. Treatment times of up to 60 s showed only minimal adverse reactions in healthy mucosa. CAP could be a promising new therapeutic modality for ENT infections. (C) 2018 Elsevier B.V. All rights reserved.