Antimicrobial effect of low-temperature argon plasma on surgical infection in vitro

Introduction. Low-temperature argon plasma (LTAP) has been widely studied as an alternative approach to prevention of purulent infections in cases of reduced germicide effectiveness due to the developed pathogen resistance. Objective. Survival assessment of opportunistic pathogens under the action of LTAP exposure in in vitro models. Materials and methods. The study was carried out using ESKAPE clinical strains (a “superbug” group with a high epidemic potential for the formation of hospital strains) and reference strains from culture collections, as well as strain mixtures. A PLASMORAN plasma arc unit (Russia) was used as a LTAP source. One plasma generation mode, three distance variants (from the nozzle to the Petri dish culture plane — 10, 15, and 20 cm), four LTAP exposure options (15, 30, 45 s for bacteria and 30, 45, and 60 s for fungi) were used. Pathogens survival after LTAP exposure in vitro was assessed by bacterial growth inhibition. Results. LTAP showed a significant antimicrobial action against clinical strains of ESKAPE Gram-negative bacteria K. pneumoniae , R. aeruginosa , A. baumanii , E. coli , Gram-positive bacteria MRSA and yeast-like fungi C. albicans under an exposure duration of 30–45 s for bacteria (the required dose of UV-A radiation is 37.8 J/m 2 UV-B 15.9 J/m 2 UV-C 34.2 J/m 2 ) and a distance of 10–15 cm from the plasma generator nozzle. The antimicrobial effect is manifested in the absence of pathogen growth on culture media at the site of LTAP exposure at a certain exposure dose, duration, and distance. This effect ensures a decrease in the titer of viable microorganisms not only in monocultures, but also in bacterial associations, both in reference strains from culture collections and in ESKAPE clinical strains. Conclusions. PLASMORAN-generated LTAP exhibits significant antibacterial and antifungal effects with respect to both reference strains from culture collections and ESKAPE clinical strains. The efficacy of LTAP action ensures a decrease in the titer of viable microorganisms from 10 8 –10 9 CFU to single CFU. The greatest effect of LTAP conditions (UV-A radiation dose of 37.8 J/m 2 ; UV-B 15.9 J/m 2 ; UV-C 34.2 J/m 2 ) on bacterial cultures is observed under a distance of 10–15 cm and an exposure duration of 30–45 s. The optimal conditions for fungi (UV-A radiation dose of 168.6 J/m 2 ; UV-B 68.4 J/m 2 ; UV-C 159 J/m 2 ) are a distance of 10 cm and an exposure duration of 60 s. Under standard dose, exposure duration, and distance, A. baumannii and E. faecium are more resistant to LTAP action than other studied bacteria. C. albicans is more resistant to LTAP action compared to bacteria, requiring a longer exposure and a shorter distance from the plasma generator nozzle to the treated surface. The results obtained require further study.