Project description:Salmonella Heidelberg is currently the 9th common serovar and has more than twice the average incidence of blood infections in Salmonella. A recent Salmonella Heidelberg outbreak in chicken infected 634 people during 2013-2014, with a hospitalization rate of 38% and an invasive illness rate of 15%. While the company’s history suggested longstanding sanitation issues, the strains’ characteristics which may have contributed to the outbreak are unknown. We hypothesized that the outbreak strains of S. Heidelberg might possess enhanced stress tolerance or virulence capabilities. Consequently, we obtained nine food isolates collected during the outbreak investigation and several reference isolates and tested their tolerance to processing stresses, their ability to form biofilms, and their invasiveness in vitro. We further performed RNA-sequencing on three isolates with varying heat tolerance to determine the mechanism behind our isolates’ enhanced heat tolerance. Ultimately, we determined that (i) many Salmonella Heidelberg isolates associated with a foodborne outbreak have enhanced heat resistance (ii) Salmonella Heidelberg outbreak isolates have enhanced biofilm-forming ability under stressful conditions, compared to the reference strain (iii) exposure to heat stress may also increase Salmonella Heidelberg isolates’ antibiotic resistance and virulence capabilities and (iv) Salmonella Heidelberg outbreak-associated isolates are primed to better survive stress and cause illness. This data helps explain the severity and scope of the outbreak these isolates are associated with and can be used to inform regulatory decisions on Salmonella in poultry and to develop assays to screen isolates for stress tolerance and likelihood of causing severe illness.
Project description:The 2017-2019 foodborne outbreak of Salmonella enterica serovar Reading (S. Reading) in North America revealed the need for effective control of this serovar in turkey production. This study evaluated two live-attenuated Salmonella vaccines against an outbreak-associated strain of S. Reading in turkeys. At 1 day and 3 weeks of age, male turkey poults were either mock-vaccinated or given either an internally developed cross-protective vaccine and a commercially available vaccine. At 7 weeks of age, poults were challenged with S. Reading; one mock-vaccinated group was mock-challenged. Along with assessment of Salmonella colonization and dissemination, acute transcriptomic responses in the cecal tonsil were characterized at 2 days post inoculation and revealed decreased expression of genes encoding intestinal transporters and tight junction proteins. Vaccination with either vaccine mitigated most of the transcriptional changes in intestinal health-related genes induced by S. Reading in turkey cecal tonsil.
Project description:Multidrug-resistant (MDR; resistance to >3 antimicrobial classes) Salmonella enterica serovar I 4,[5],12:i:- strains were linked to a 2015 foodborne outbreak from pork. Strain USDA15WA-1, associated with the outbreak, harbors an MDR module and the metal tolerance element Salmonella Genomic Island 4 (SGI-4). Characterization of SGI-4 revealed that conjugational transfer of SGI-4 resulted in the mobile genetic element (MGE) replicating as a plasmid or integrating into the chromosome. Tolerance to copper, arsenic, and antimony compounds was increased in Salmonella strains containing SGI-4 compared to strains lacking the MGE. Following Salmonella exposure to copper, RNA-seq transcriptional analysis demonstrated significant differential expression of diverse genes and pathways, including induction of numerous metal tolerance genes (copper, arsenic, silver, and mercury). Evaluation of swine administered elevated concentrations of zinc oxide (2,000 mg/kg) and copper sulfate (200 mg/kg) as an antimicrobial feed additive (Zn+Cu) in their diet for 4 weeks prior to and 3 weeks post-inoculation with serovar I 4,[5],12:i:- indicated that Salmonella shedding levels declined at a slower rate in pigs receiving in-feed Zn+Cu compared to control pigs (no Zn+Cu). The presence of metal tolerance genes in MDR Salmonella serovar I 4,[5],12:i:- may provide benefits for environmental survival or swine colonization in metal-containing settings.
Project description:This study aimed to compare differentially expressed transcripts in Salmonella recovered from the inoculated onion bulbs using transcriptome profiling (RNA-seq). The Salmonella strains of Salmonella enterica subsp. enterica ser. Newport, isolated from clinical cases affected by the onion-linked outbreak in 2020 (CDC, 2020), was used for the onion bulb inoculation. Transcriptomic analysis of Salmonella was performed 1 day (24 hours) and 7 days post-inoculation to identify Differentially Expressed Genes (DEGs) . 925 and 736 genes were upregulated within 24 hours and seven days after inoculation, while the number of downregulated genes in the same timeframe was 690 and 826, respectively (FDR<0.05 and Abs (log 2(Y/X) >0).