Comparison of inactivation characteristics of Escherichia coli and Staphylococcus aureus in water by rotary plasma jet sterilization

Abstract

This study aims to investigate the differential inactivation responses of Escherichia coli and Staphylococcus aureus under rotary plasma jet conditions. Initially, we examined the antimicrobial effects of the rotary plasma jet on the two microorganisms under various operational parameters. Under optimal conditions (power: 1000 W, frequency: 30 kHz, flow rate: 45 NL/min, height: 4 cm, duration: 70 s), the treatment achieved an impressive 99.9 % inactivation of both bacterial strains. Notably, Staphylococcus aureus exhibited more excellent resistance when compared to Escherichia coli. Subsequently, we delved into changes in cell viability, cell granularity, and intracellular reactive oxygen species (ROS) levels before and after rotary spray plasma jet treatment to explore the differential inactivation mechanisms of the two microbial species. Cell viability assessments unveiled reduced viable cells and increased occurrence of dead cells and late-stage apoptotic cells for both microbial types, potentially attributed to augmented cell permeability and damage. Compared to Staphylococcus aureus, Escherichia coli exhibited notable enhancements in forward scatter (FSC) and side scatter (SSC) cell granularity detection signals yet displayed lower intracellular ROS levels. This discrepancy suggests that the primary cause of Escherichia coli inactivation may be cell envelope disruption. In contrast, Excessive intracellular ROS accumulation could be responsible for the inactivation of Staphylococcus aureus.