Argon plasma-activated liquid inactivates Helicobacter pylori and resistant hospital pathogens through acidification...

The rise of antibiotic-resistant bacteria is a major public health concern. Physical plasma can generate reactive oxygen and nitrogen species (RONS) with antimicrobial activity. Plasma-activated liquid (PAL) can be used as a carrier for RONS. This study investigated the antibacterial effects of PAL against clinically relevant Gram-negative (Escherichia coli, multidrug-resistant (MDR) Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae, Klebsiella pneumoniae, and Helicobacter pylori) and Gram-positive (Staphylococcus aureus and Enterococcus faecium) bacteria.

A commercial argon plasma electrosurgical source was used to produce PAL from 0.9% NaCl solution. PAL-NaCl showed strong bactericidal effects: MDR E. coli was completely eradicated (>6 log₁₀ reduction) within 60 min. H. pylori was reduced by ~4.5 log₁₀ within 15 min and completely eradicated (>5 log₁₀) within 60 min of exposure. Gram-negative bacteria were highly susceptible with a mean reduction of ~6.3 log₁₀, whereas Gram-positive bacteria showed lower susceptibility with a mean reduction of ~2.6 log₁₀. Antibacterial activity was associated with acidic pH and influenced by carrier solution chemistry, consistent with a contribution of short-lived secondary reactive nitrogen species. The scavenger 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron(III) chloride (FeTPPS), targeting peroxynitrite (ONOO^-), partially inhibited the antibacterial effect, supporting its mechanistic importance. Buffered solutions (higher pH) showed minimal antibacterial activity despite higher absolute RONS concentrations which underlines the importance of the acidic environment.

PAL generated with an argon plasma electrosurgical source exhibits potent antibacterial activity, driven by low pH and RONS dynamics. PAL effectively inactivates MDR pathogens and other clinically relevant pathogens, including H. pylori. The stomach's acidic environment may enhance PAL activity by maintaining the low-pH conditions required for pH-dependent reactive nitrogen chemistry associated with antibacterial efficacy.