Identification of pathways required for Salmonella to colonise alfalfa using TraDIS-Xpress.

Holden E, Abi Assaf J, Al-khanaq H, Vimont N, Webber M, Trampari E. (2023)

Applied and Environmental Microbiology

Enteropathogenic bacteria, such as Salmonella, have been linked to numerous fresh produce outbreaks, posing a significant public health threat. Salmonellas ability to persist on fresh produce for extended periods is partly attributed to its capacity to form biofilms, which pose a challenge to food decontamination and can increase pathogenic bacterial load in the food chain. Preventing Salmonella colonisation of food products and  food processing environments is crucial for reducing the incidence of foodborne outbreaks. Understanding the mechanisms of establishment on fresh produce will inform the development of decontamination approaches. We used Transposon-Directed Insertion site Sequencing (TraDIS-Xpress) to investigate the mechanisms employed by Salmonella enterica serovar Typhimurium to colonise and establish on fresh produce over time. We established an alfalfa colonisation model and compared the findings to those obtained from glass surfaces. Our research identified distinct mechanisms required for Salmonella establishment on alfalfa compared to glass surfaces over time. These include the type III secretion system (sirC), Fe-S cluster assembly (iscA), curcumin degradation (curA) and copper tolerance (cueR). Shared pathways across surfaces included NADH hydrogenase synthesis (nuoA, nuoB) , fimbrial regulation (fimA, fimZ), stress response (rpoS), LPS O-antigen synthesis ( rfbJ), iron acquisition (ybaN) and ethanolamine utilisation (eutT, eutQ). Notably, flagella biosynthesis differentially impacted colonisation of biotic and abiotic environments over time. Understanding the genetic underpinnings of Salmonella establishment on both biotic and abiotic surfaces over time offers valuable insights that can inform the development of targeted antibacterial therapeutics, ultimately enhancing food safety throughout the food processing chain.

Applied and Environmental Microbiology

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