Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2009
Publication Date: 5/20/2009
Citation: Bearson, S.M., Bearson, B.L., Lee, I. 2009. The Poxr Gene of Salmonella Enterica Serovar Typhimurium is Involved in Stress Survival and Swine Colonization [abstract]. American Society for Microbiology Meeting. p. 619.
Technical Abstract: Mutations in the poxR gene (STM4344; yjeA; poxA) of Salmonella enterica serovar Typhimurium (S. Typhimurium) have previously been shown to cause several phenotypic alterations including reduced pyruvate oxidase activity, virulence attenuation in the mouse model, and enhanced sensitivity to various bacterial growth inhibitors such as antibiotics, dyes and the antimicrobial peptide protamine. Our research group identified a mutation in the poxR gene during a S. Typhimurium signature-tagged mutagenesis screen to identify genes important for survival in the harsh environment of the swine stomach, a first line of defense against foodborne pathogens. Not only was the poxR mutant ~20-fold more sensitive in the ex vivo swine stomach content assay than the parental strain, but the poxR mutant was also more sensitive to pH 3.0 acidic challenge. To determine if the mutation in poxR affects colonization of the swine gastrointestinal tract, eight week old pigs were intranasally inoculated with either the chi4232 S. Typhimurium parent strain or the poxR mutant (n = 5 for each group). Fecal shedding of the poxR mutant was significantly reduced during the 7-day study compared to the wild-type strain at 1, 2, 3, 5 and 7 days post-inoculation (dpi), as was the presence of the mutant in the cecal contents of the pigs and colonization of the cecal tissue at 7 dpi (p < 0.05). Colonization of the Peyer’s Patch region of the ileum trended towards significance with a p-value = 0.075, but colonization of the ileocecal lymph nodes was identical for swine inoculated with the mutant versus the wild-type strain. As a predicted lysyl-tRNA synthetase, reduction in PoxR levels could alter which mRNA transcripts are translated, thereby changing the protein profile of the pathogen and affecting a variety of bacterial processes including stress survival and host colonization.