Nonthermal Atmospheric Plasma Rapidly Disinfects Multidrug-Resistant Microbes by Inducing Cell Surface Damage

Abstract

Plasma, a unique state of matter with properties similar to those of ionized gas, is an effective biological disinfectant. However, the mechanism through which nonthermal or "cold" plasma inactivates microbes on surfaces is poorly understood, due in part to challenges associated with processing and analyzing live cells on surfaces rather than in aqueous solution. Here, we employ membrane adsorption techniques to visualize the cellular effects of plasma on representative clinical isolates of drug-resistant microbes. Through direct fluorescent imaging, we demonstrate that plasma rapidly inactivates planktonic cultures, with >5 log 10 kill in 30 s by damaging the cell surface in a time-dependent manner, resulting in a loss of membrane integrity, leakage of intracellular components (nucleic acid, protein, ATP), and ultimately focal dissolution of the cell surface with longer exposure time. This occurred with similar kinetic rates among methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Candida albicans. We observed no correlative evidence that plasma induced widespread genomic damage or oxidative protein modification prior to the onset of membrane damage. Consistent with the notion that plasma is superficial, plasma-mediated sterilization was dramatically reduced when microbial cells were enveloped in aqueous buffer prior to treatment. These results support the use of nonthermal plasmas for disinfecting multidrug-resistant microbes in environmental settings and substantiate ongoing clinical applications for plasma devices. P lasmas are ionized gases that exhibit a plethora of applied temperature and physical properties. In biomedical applications, plasmas are supported by an electric field such that electrons receive external energy more rapidly than surrounding ions (5). Plasmas generate thermal energy (heat) when heavy particle temperatures equilibrate with electron temperature but are considered "nonthermal" when the cooling of ions and uncharged molecules is more effective than the energy transfer from electrons to gas (5). Nonthermal or "cold" plasmas produce a variety of shortlived and long-lived reactive components, including charged particles and UV radiation, without significantly raising temperature (25). Nonthermal plasmas (NTPs) are applied extensively in materials science to modify the properties of carbon-based materials but have also shown promise for applications in biology and med-

Inhibition of methicillin resistant Staphylococcus aureus by a plasma needle

“…Independent of our work, Joshi et al reached similar conclusions [13]. A large number of papers followed [31][32][33]. In this sense, biofilms represent an even more challenging task because bacteria are shielded by the polymeric matrix.…”

Antibacterial Activity of Bisanthraquinone (+)-1,1’-Bislunatin

“…The result of the present study showed that generally, the MIC value of bacteria exposed to (+)- Evidently exposure to (+)-1,1'-bislunatin caused an obvious change in the permeability of bacterial cell membrane and degeneration of cell membrane. According to Kvam et al (2012) the cell poration and lysis are believed to be indicators of gradual cellular protein and nucleic acid leakage from the cell. The observation on cellular morphology showed that the bacteria cells deflated after treatment with (+)-1,1'-bislunatin, causing losses of cell wall function as protector or barrier between organs and cellular fluid.…”

Terminal sterilization: Conventional methods versus emerging cold atmospheric pressure plasma technology for non‐viable biological tissues

“…Examples reported of CAP capability for decontaminating multidrug resistant bacteria including the highly resistant MRSA [109][110][111] and Pseudomonas aeruginosa. [110] Notably, CAP is also effective on the sterilization resistant Deinococcus radiodurans bacteria.…”

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