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Title:   Author  item
                                            Bearson, Bradley

                                                         - *Brad*item
                                            Brunelle, Brianitem
                                            LEE, IN - Hannam University
  Submitted to: Meeting Abstract
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 9/23/2014
                                    Publication  Date: 10/11/2014
                                    Citation: Bearson, B.L., Brunelle, B.W., Lee, I.S. 2014. RNA-seq analysis of prophage induction in multidrug-resistant salmonella enterica serovar typhimurium DT104 following exposure to the agricultural antibiotic carbadox. Meeting Abstract. 74th Annual Meeting North Central Branch of the American Society of Microbiology.Interpretive Summary:
                                Technical Abstract: Non-typhoidal Salmonella is a leading cause of U.S. foodborne disease and food-related deaths. Multidrug-resistant (MDR) Salmonella Typhimurium DT104 contains 5 prophages in the genome that may be induced to produce phage under various environmental conditions, including antibiotic exposure. We investigated phage induction in MDR DT104 following exposure to carbadox, an antibiotic used in the U.S., during the starter phase of swine production for performance enhancement and enteric disease control. Sub-inhibitory concentrations of carbadox induced phage production and cell lysis in DT104, and RNA-seq analysis identified 3 prophages (homologs of Gifsy-1, ST64B, and P22) with significantly increased gene expression. Also, we demonstrated that the P22 homolog is capable of genetic transfer of non-phage DNA to a recipient S. Typhimurium by generalized transduction, including transfer of Salmonella chromosomal DNA and plasmid DNA that confers antibiotic resistance. We created prophage deletion mutants, 'Gifsy-1, 'ST64B, and 'Gifsy-1 'ST64B, and RNA-seq analysis revealed increased expression of P22 prophage genes in these mutants following carbadox exposure. Furthermore, a carbadox-induced phage lysate from a 'Gifsy-1 'ST64B double mutant (P22-like+) facilitated a >10-fold increase in gene transfer by transduction compared to wild-type DT104; this finding suggests that competition between phage production and phage-mediated, bacterial cell lysis may limit generalized transduction efficiency via P22 prophage from wild-type DT104. Thus, carbadox exposure of MDR DT104 induces multiple prophages and facilitates transduction of antibiotic resistance to susceptible Salmonella hosts. Investigations of Salmonella prophage induction in pigs fed a carbadox-containing diet may be warranted as swine are often asymptomatically colonized with Salmonella.


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