Comparative analysis of direct and indirect non-thermal argon plasma treatment against multidrug-resistant hospital-acquired pathogens: an in-vitro investigation

Non-thermal plasma (NTP) represents an innovative approach in combating antimicrobial resistance, particularly when conventional chemical agents show limited efficacy. This study evaluated the susceptibility of clinically significant pathogens to NTP treatment, examining both direct plasma exposure and plasma-activated water (PAW) applications. The investigation encompassed 15 bacterial strains, including 10 drug-resistant clinical isolates and 5 standard clinical isolates, with a focus on determining optimal treatment parameters and antimicrobial efficacy. Systematic evaluation of exposure parameters included direct NTP application and PAW treatment across various time intervals (15-240 seconds). Complete bacterial inactivation was achieved within 15-30 seconds of direct NTP exposure for all tested species (initial concentration 109 CFU/mL). Notably, methicillin-resistant Staphylococcus aureus (MRSA) exhibited particular sensitivity to NTP treatment, demonstrating a statistically significant 9-log reduction in viable cells (p < 0.05). PAW treatment showed comparable efficacy, achieving significant bacterial reduction after 180-240 seconds of exposure, with optimal antimicrobial activity observed in freshly prepared PAW (Day 0). While antimicrobial efficacy gradually decreased during storage, significant activity was maintained through Day 7. Time-kill studies confirmed complete bacterial eradication following direct NTP exposure, with no evidence of bacterial regrowth during extended incubation periods. These findings demonstrate NTP's potential as an effective alternative for microbial decontamination in healthcare settings, particularly for surface sterilization applications. The study provides compelling evidence for NTP's role in addressing both antibiotic-resistant and susceptible pathogens, offering a promising tool for infection control strategies.