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Infect Immun. 2017 May 23;85(6). pii: e01067-16. doi: 10.1128/IAI.01067-16. Print 2017 Jun.

Analysis of Shigella flexneri Resistance, Biofilm Formation, and Transcriptional Profile in Response to Bile Salts.

Author information

1
Mucosal Immunology and Biology Research Center, Division of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
2
Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA.
3
Institute for Genome Sciences, Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
4
Center for Vaccine Development, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA.
5
Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
6
Mucosal Immunology and Biology Research Center, Division of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA csfaherty@partners.org.

Abstract

The Shigella species cause millions of cases of watery or bloody diarrhea each year, mostly in children in developing countries. While many aspects of Shigella colonic 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 in Shigella flexneri strain 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 the Enterobacteriaceae Characterization of S. flexneri 2457T 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 in S. flexneri 2457T, 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 that S. flexneri 2457T 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 activate S. flexneri 2457T virulence. This work provides insights into how exposure to bile likely regulates Shigella survival and virulence during host transit and subsequent colonic infection.

KEYWORDS:

EPS matrix; Escherichia coli; Shigella; bile salts; biofilm; resistance; virulence; virulence genes

PMID:
28348056
PMCID:
PMC5442615
DOI:
10.1128/IAI.01067-16
[Indexed for MEDLINE]
Free PMC Article

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