In vivo bioluminescence imaging of Escherichia coli O104:H4 and role of aerobactin during colonization of a mouse model of infection

Alfredo G. Torres, Roberto J. Cieza, Maricarmen Rojas-Lopez, Carla A. Blumentritt, Cristiane S. Souza, R. Katie Johnston, Nancy Strockbine, James B. Kaper, Elena Sbrana, Vsevolod L. Popov

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15 Scopus citations

Abstract

Background: A major outbreak of bloody diarrhea associated with Shiga toxin-producing Escherichia coli O104:H4 occurred early in 2011, to which an unusual number of hemolytic uremic syndrome cases were linked. Due to limited information regarding pathogenesis and/or virulence properties of this particular serotype, we investigated the contribution of the aerobactin iron transport system during in vitro and in vivo conditions. Results: A bioluminescent reporter construct was used to perform real-time monitoring of E. coli O104:H4 in a mouse model of infection. We verified that our reporter strain maintained characteristics and growth kinetics that were similar to those of the wild-type E. coli strain. We found that the intestinal cecum of ICR (CD-1) mice was colonized by O104:H4, with bacteria persisting for up to 7 days after intragastric inoculation. MALDI-TOF analysis of heat-extracted proteins was performed to identify putative surface-exposed virulence determinants. A protein with a high similarity to the aerobactin iron receptor was identified and further demonstrated to be up-regulated in E. coli O104:H4 when grown on MacConkey agar or during iron-depleted conditions. Because the aerobactin iron acquisition system is a key virulence factor in Enterobacteriaceae, an isogenic aerobactin receptor (iutA) mutant was created and its intestinal fitness assessed in the murine model. We demonstrated that the aerobactin mutant was out-competed by the wildtype E. coli O104:H4 during in vivo competition experiments, and the mutant was unable to persist in the cecum. Conclusion: Our findings demonstrate that bioluminescent imaging is a useful tool to monitor E. coli O104:H4 colonization properties, and the murine model can become a rapid way to evaluate bacterial factors associated with fitness and/or colonization during E. coli O104:H4 infections.

Original languageEnglish (US)
Article number112
JournalBMC Microbiology
Volume12
DOIs
StatePublished - Jun 22 2012

ASJC Scopus subject areas

  • Microbiology
  • Microbiology (medical)

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    Torres, A. G., Cieza, R. J., Rojas-Lopez, M., Blumentritt, C. A., Souza, C. S., Johnston, R. K., Strockbine, N., Kaper, J. B., Sbrana, E., & Popov, V. L. (2012). In vivo bioluminescence imaging of Escherichia coli O104:H4 and role of aerobactin during colonization of a mouse model of infection. BMC Microbiology, 12, [112]. https://doi.org/10.1186/1471-2180-12-112