The inactivation efficacy of plasma-activated acetic acid against Salmonella Typhimurium cells and biofilm.

Abstract

This study aimed to examine the inactivation efficacy of plasma-activated acetic acid (PAAA) against Salmonella Typhimurium cells and biofilm and elucidate underlying chemical inactivation pathway. PAAA was prepared by discharging plasma to 20 ml of 0.2% (v/v) acetic acid (AA) for 20 min (2.2kHz and 8.4kVpp). The count of cells and biofilms decreased by 5.71 log CFU ml-1 and 4 log CFU/cm2 after 10min of treatment with 0.2% PAAA and 0.4% PAAA compared with control group (without any treatment), respectively. In 0.2% PAAA, the concentrations of hydrogen peroxide (H2 O2 ) and nitrate anions were directly proportional to the plasma discharge time, whilst nitrite anion (NO2 - ) was not detected. However, the pH values of both 0.2% PAAA and plasma-activated water were inversely proportional to the plasma discharge time. Treatment with catalase, L-histidine, D-mannitol and sodium azide inhibited the antibacterial activity of PAAA. H2 O2 , singlet oxygen, hydroxyl radical and NO2 - are involved in the generation and decomposition of peroxynitrous acid generated from PAAA functioned as intermediate agent, which could diffuse through cell membranes of bacteria and induce cell injury. This study provides the understanding of efficacy and selectivity of PAAA which could be a novel decontamination agent.