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Title:   Author  item
                                            Bearson, Bradley

                                                         - *Brad*item
                                            Bearson, Shawn
  Submitted to: American Society for Microbiology
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 8/14/2007
                                    Publication  Date: 10/10/2007
                                    Citation: Bearson, B.L., Bearson, S.M. 2007. The role of the QseC sensor kinase in Salmonella enterica serovar Typhimurium quorum sensing and swine colonization [abstract].  In: Proceedings of 3rd American Society for Microbiology Conference on Cell-Cell Communication in Bacteria, October 7-10, 2007, Austin, Texas. p. 34, 20A.Interpretive Summary:
                                Technical Abstract: At least two quorum sensing molecules, autoinducer-3 (AI-3) and norepinephrine (NE), are present in the gastrointestinal tract and activate the E. coli QseBC quorum sensing system.  AI-3 is produced by enteric bacteria, whereas NE is produced by the animal host, often during stress.  Both 10% pre-conditioned medium (AI-3) from the wild-type strain and NE enhanced motility of Salmonella enterica serovar Typhimurium on 0.3% DMEM motility medium.  The enhanced motility of Salmonella in the presence of NE and pre-conditioned medium was prevented by phentolamine, an alpha-adrenergic antagonist.  To investigate the role of the QseBC quorum sensing system in Salmonella pathogenicity, a mutation in the qseC gene, encoding the QseC sensor kinase, was constructed and the mutant was analyzed for invasion (in vitro) and colonization (in vivo).  The qseC mutant exhibited a 4-fold decrease (p<0.002) in invasion of non-polarized IPEC-J2 porcine jejunal epithelial cells compared to wild-type S. Typhimurium.  To determine whether the QseC sensor kinase is important for Salmonella colonization of the porcine gastrointestinal tract, a qseC mutant and the wild-type strain were intranasally inoculated into swine at a 1:1 ratio.  Quantitative bacteriology was performed daily to determine competitive fitness of the mutant and parent strains.  Over the 7-day sampling period (n=6), fecal shedding of the qseC mutant was significantly reduced 5- to 30-fold (p<0.01) compared to the wild-type strain.  Necropsies (n=3) were performed at 7 d.p.i. and tissue samples of the gastrointestinal tract were obtained for quantitative bacteriology.  The competitive fitness of the qseC mutant was respectively reduced 23-, 15- and 40-fold (p<0.05) in the ileal Peyer’s Patches, ileocecal lymph nodes and cecum compared to the wild-type strain.  Interestingly, the difference in colonization of the tonsils between the qseC mutant and the wild-type strain was only 2.5-fold.  This research demonstrates that the S. Typhimurium qseC mutant has reduced colonization of the swine gastrointestinal tract and suggests that the detection of chemical signals via the QseBC quorum sensing system is important for host colonization.


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