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Title:   Author  item
                                            Brunelle, Brianitem
                                            Bearson, Shawnitem
                                            Bearson, Bradley

                                                         - *Brad*
  Submitted to: Meeting Abstract
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 8/9/2013
                                    Publication  Date: 10/9/2013
                                    Citation: Brunelle, B.W., Bearson, S.M., Bearson, B.L. 2013. Tetracycline promotes the expression of ten fimbrial operons in specific Salmonella enterica serovar Typhimurium isolates [abstract]. In: Proceedings of 4th American Society of Microbiology Conference on Salmonella: The Bacterium, the Host and the Environment, May 17-20, 2014, Boston, Massachusetts. p. 113.Interpretive Summary:
                                Technical Abstract: Multidrug-resistant (MDR) Salmonella is associated with increased morbidity in humans and presents an important food safety concern. Antibiotic resistance among isolates of Salmonella enterica serovar Typhimurium has become especially prevalent as over 27 per cent of isolates from humans in the United States are resistant to three or more antibiotics. Because antibiotics can affect cellular processes in bacteria, our goal was to establish differences in transcriptional regulation due to tetracycline exposure in MDR S. Typhimurium isolates. We have previously shown that tetracycline exposure during early-log growth in vitro can induce a fully invasive phenotype in several MDR S. Typhimurium DT193 isolates; Salmonella is typically invasive during late-log to stationary phase, but has little-to-no invasive capabilities during early-log. We used RNA-seq to ascertain changes in global gene expression in these DT193 isolates after exposure to tetracycline for 30 minutes versus the same isolates not treated with the antibiotic. The transcriptomic analyses detected genes associated with motility are down-regulated, while SPI-1, SPI-2, SPI-3 and attachment genes are up-regulated. Within the genes associated with attachment, ten fimbrial operons (bcf, csg, fim, lpf, saf, stb, stc, std, stf, and sth) were up-regulated. This is unusual as only lpf and csg operons are considered to be inducible in vitro, and normally induction does not occur until a much later growth phase. The other fimbrial genes are only expressed in vivo, with previous studies indicating that the bcf, lpf, stb, stc, std, and sth operons are associated with persistence in mice. Visualization of the isolates by electron microscopy indicated that isolates treated with tetracycline had fewer flagella and increased agglutination, which is consistent with the RNA-seq data. Our study demonstrates that tetracycline promotes the expression of fimbrial genes that are linked to increased colonization and persistence in the host; such an effect may play a role in increasing the duration and intensity of a MDR Salmonella infection.


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