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

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 wild-type 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.

• Authors: 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
• Journal: BMC microbiology (BMC Microbiol) Vol. 12 Pg. 112 (Jun 20 2012) ISSN: 1471-2180 [Electronic] England
• PMID: 22716772 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Hydroxamic Acids
• Virulence Factors
• aerobactin
• Iron

Topics

• Animals
• Cecum (microbiology)
• Disease Models, Animal
• Escherichia coli (genetics, growth & development, metabolism, pathogenicity)
• Escherichia coli Infections (microbiology, pathology)
• Female
• Gene Deletion
• Hydroxamic Acids (metabolism)
• Iron (metabolism)
• Mice
• Mice, Inbred ICR
• Virulence
• Virulence Factors (genetics, metabolism)
• Whole Body Imaging (methods)