Transcriptome Response of Salmonella Newport to Oxidative Antimicrobials

Introduction: Transfer of foodborne pathogens such as Salmonella from agricultural waters to produce presents a prominent issue in food safety. While mitigation strategies exist to reduce or eliminate this possibility, many factors such as environmental conditions and microbial response can affect the overall efficacy of these methods. Investigating genetic response to commonly used oxidative antimicrobials such as sodium hypochlorite (NaOCl) and peroxyacetic acid (PAA) may elucidate aspects of this complex interaction. Further understanding of pathogen response to antimicrobials may increase efficacy of disinfection systems.

Purpose:  The purpose of this study was to analyze the genetic response of an outbreak strain of SalmonellaNewport upon exposure to two commonly used antimicrobials.

Methods:  Salmonella Newport was exposed to NaOCl (pH 6.5) and PAA at concentrations of 0, 10 and 20 ppm each for 30 seconds. Treatments were conducted with two samples per treatment repeated in duplicate. Following exposure, cells were isolated and RNA extracted for sequencing. Transcriptomes were compared between treatments and control (0 ppm) for significantly up or down-regulated genes (FDR P≤0.05).

Results: Significant upregulation of electron transport chain-associated genes was noted in both PAA treatments up to 47.4-fold and 54.0-fold, respectively (P<0.05), and 20 ppm PAA showed up to a 296.0 and 195.2-fold increase in citrate and shikimate degradation, respectively. While 10ppm NaOCl treatments resulted in minimal significant induced changes comparatively, upregulations were noted in cellular membrane associated proteins (up to 3.5-fold), protein synthesis associated components (up to 21.4-fold), as well as redox-stress associated transcriptional regulation (up to 2.4-fold). Upregulation of protein synthesis components was also seen in 20 ppm NaOCl up to 242.2-fold and phage-associated genes up to 40.3-fold.

Significance: Observed trends in gene induction lend to the need for further investigation of microbial response to antimicrobials to ensure effective mitigation strategies.