title: Analysis of Shigella flexneri Resistance, Biofilm Formation, and Transcriptional Profile in Response to Bile Salts.
abstract: TheShigellaspecies cause millions of cases of watery or bloody diarrhea each year, mostly in children in developing countries. While many aspects ofShigellacolonic cell invasion are known, crucial gaps in knowledge regarding how the bacteria survive, transit, and regulate gene expression prior to infection remain. In this study, we define mechanisms of resistance to bile salts and build on previous research highlighting induced virulence inShigella flexneristrain 2457T following exposure to bile salts. Typical growth patterns were observed within the physiological range of bile salts; however, growth was inhibited at higher concentrations. Interestingly, extended periods of exposure to bile salts led to biofilm formation, a conserved phenotype that we observed among members of theEnterobacteriaceaeCharacterization ofS. flexneri2457T biofilms determined that both bile salts and glucose were required for formation, dispersion was dependent upon bile salts depletion, and recovered bacteria displayed induced adherence to HT-29 cells. RNA-sequencing analysis verified an important bile salt transcriptional profile inS. flexneri2457T, including induced drug resistance and virulence gene expression. Finally, functional mutagenesis identified the importance of the AcrAB efflux pump and lipopolysaccharide O-antigen synthesis for bile salt resistance. Our data demonstrate thatS. flexneri2457T employs multiple mechanisms to survive exposure to bile salts, which may have important implications for multidrug resistance. Furthermore, our work confirms that bile salts are important physiological signals to activateS. flexneri2457T virulence. This work provides insights into how exposure to bile likely regulatesShigellasurvival and virulence during host transit and subsequent colonic infection.
authors.affiliation: Mucosal Immunology and Biology Research Center, Division of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.|Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Kourtney P
authors.initials: KP
authors.lastname: Nickerson
authors.affiliation: Mucosal Immunology and Biology Research Center, Division of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.|Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Rachael B
authors.initials: RB
authors.lastname: Chanin
authors.affiliation: Institute for Genome Sciences, Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Jeticia R
authors.initials: JR
authors.lastname: Sistrunk
authors.affiliation: Institute for Genome Sciences, Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: David A
authors.identifier: http://orcid.org/0000-0002-7337-7154
authors.initials: DA
authors.lastname: Rasko
authors.affiliation: Mucosal Immunology and Biology Research Center, Division of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.|Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Fink
authors.affiliation: Center for Vaccine Development, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Barry
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: Nataro
authors.affiliation: Mucosal Immunology and Biology Research Center, Division of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA csfaherty@partners.org.|Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Christina S
authors.initials: CS
authors.lastname: Faherty
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D020869:Gene Expression Profiling; D019073:HT29 Cells; D006367:HeLa Cells; D006801:Humans; D008854:Microscopy, Electron; D009154:Mutation; D019081:O Antigens / Q000235:genetics / Q000378:metabolism*; D017423:Sequence Analysis, RNA; D012763:Shigella flexneri / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D001647:Bile Acids and Salts; D019081:O Antigens
keywords: EPS matrix; Escherichia coli; Shigella; bile salts; biofilm; resistance; virulence; virulence genes