The Effect of the Non-thermal Plasma on the Elimination and Growth of Staphylococcus aureus and Pseudomonas aerunginosa for Medical Applications

Pathogenic bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa found in hospitals may cause gastroenteritis, skin diseases, and pneumonia. Recently, atmospheric plasma have been tested for bio-medical and environmental applications including air pollution control, wastewater cleaning, bio-decontamination, surface sterilization, and treatment of skin diseases. The objective of this study is to determine the optimal dosage of the non-thermal plasma to significantly reduce or to eliminate pathogenic bacteria and to study its effect on bacterial re-growth after plasma treatment. S. aureus and P. aeruginosa at low (15-26 CFU/ 1.5 µl) and high (~10⁷ to 10⁸ CFU/ml) concentrations were exposed to plasma at different times (0 s to 360 s). Percentage of elimination and log reductions were calculated after incubation based on initial bacterial concentration and survived bacteria after treatment. Survived colonies after 60 s and 35 s of treatment were transferred to tryptic soy broth (TSB) to observe bacterial re-growth. Bacterial concentrations (CFU/ml) were determined over 24 hours at different time intervals. Experiments were performed three times with duplicates. The results show that at low concentrations, 96% of elimination was achieved after 180 s for S. aureus and 100% of elimination after 60 s for P. aeruginosa. At high concentrations of S. aureus and P. aeurginosa, we have observed 2.4 and 3.9 log 10 reductions after 360 s of treatment. Survived bacteria were able to re-grow at the same growth rate compared to the control. These results suggest the potential use of the non-thermal plasma on elimination of pathogenic bacteria.