Isolation and characterization of resistant variants of Salmonella Typhimurium after sequential exposure to plasma activated water (PAW)

Abstract

Plasma-activated water (PAW) is emerging as a promising disinfectant. However, its use can inadvertently contribute to the isolation of bacterial resistant variants (RVs). In this study, four distinct populations of Salmonella enterica serovar Typhimurium were subjected to 30 cycles consisting of lethal treatments with PAW followed by recovery of survivors. One RV from each population was isolated for genotypic and phenotypic characterization. Globally, genomic analysis of four isolated RVs (SePAW1–4) uncovered mutations affecting proteins directly or indirectly related to oxidative stress response (QseC in SePAW1; ArcB in SePAW2; and ZntB, and CsrA in SePAW3); to cell envelopes (MreB in SePAW1; and MpeM, and WbaV in SePAW2); or to transcriptional factors (RpoD in SePAW4). Significantly, these genetic alterations were found to underlie the observed cross-tolerance of each RV to one or more disinfectants: a chlorine-based solution (sodium hypochlorite), an oxidative compound (peracetic acid), or an individual compound from essential oils (carvacrol).