Cold Atmospheric Air Plasma Sterilization against Spores and Other Microorganisms of Clinical Interest

TLDR

Physical cold atmospheric surface microdischarge (SMD) plasma in ambient air shows promise for sterilizing sensitive medical devices where conventional methods fail, potentially revolutionizing healthcare disinfection. The study investigates the inactivation mechanisms of SMD plasma against clinically relevant microorganisms, focusing on neutral reactive species and diagnostic methods. The authors tested SMD plasma on Gram‑negative and Gram‑positive bacteria, Candida albicans, and bacterial endospores on Tyvek coupons, and discussed neutral reactive species as key inactivation mechanisms. Thirty‑second plasma exposure achieved 4–6 log10 CFU reductions, with Candida albicans being the most resistant, and endospore D values ranged from 0.3 to 0.9 min, lower than reference methods and independent of specimen material.

Abstract

ABSTRACT Physical cold atmospheric surface microdischarge (SMD) plasma operating in ambient air has promising properties for the sterilization of sensitive medical devices where conventional methods are not applicable. Furthermore, SMD plasma could revolutionize the field of disinfection at health care facilities. The antimicrobial effects on Gram-negative and Gram-positive bacteria of clinical relevance, as well as the fungus Candida albicans , were tested. Thirty seconds of plasma treatment led to a 4 to 6 log 10 CFU reduction on agar plates. C. albicans was the hardest to inactivate. The sterilizing effect on standard bioindicators (bacterial endospores) was evaluated on dry test specimens that were wrapped in Tyvek coupons. The experimental D 23 ° C values for Bacillus subtilis , Bacillus pumilus , Bacillus atrophaeus , and Geobacillus stearothermophilus were determined as 0.3 min, 0.5 min, 0.6 min, and 0.9 min, respectively. These decimal reduction times ( D values) are distinctly lower than D values obtained with other reference methods. Importantly, the high inactivation rate was independent of the material of the test specimen. Possible inactivation mechanisms for relevant microorganisms are briefly discussed, emphasizing the important role of neutral reactive plasma species and pointing to recent diagnostic methods that will contribute to a better understanding of the strong biocidal effect of SMD air plasma.