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Infection and Immunity, November 2008, p. 4814-4822, Vol. 76, No. 11
0019-9567/08/$08.00+0     doi:10.1128/IAI.00446-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Escherichia coli O157:H7 Survives within Human Macrophages: Global Gene Expression Profile and Involvement of the Shiga Toxins{triangledown}

Katherine Poirier,1 Sébastien P. Faucher,1,2 Maxime Béland,1 Roland Brousseau,3,{dagger} Victor Gannon,4 Christine Martin,5 Josée Harel,6 and France Daigle1*

Department of Microbiology and Immunology, University of Montreal, C.P. 6128 Succursale Centre-Ville, Montréal, Québec, Canada H3C 3J7,1 Department of Microbiology, Columbia University Medical Center, New York, New York 10032,2 Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Ave., Montreal, Quebec, Canada H4P 2R2,3 Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, Lethbridge, Alberta, Canada T1J 3Z4,4 Institut National de la Recherche Agronomique, UR454 Unité de Microbiologie, Centre de Theix, 63122 Saint-Genès-Champanelle, France,5 Département de Pathologie et Microbiologie, Université de Montréal, C.P. 5000, St-Hyacinthe, Québec, Canada J2S 7C66

Received 10 April 2008/ Returned for modification 19 June 2008/ Accepted 31 July 2008

Escherichia coli O157:H7 is an important food-borne pathogen that specifically binds to the follicle-associated epithelium in the intestine, which rapidly brings this bacterial pathogen in contact with underlying human macrophages. Very little information is available about the interaction between E. coli O157:H7 and human macrophages. We evaluated the uptake and survival of strain EDL933 during infection of human macrophages. Surprisingly, EDL933 survived and multiplied in human macrophages at 24 h postinfection. The global gene expression profile of this pathogen during macrophage infection was determined. Inside human macrophages, upregulation of E. coli O157:H7 genes carried on O islands (such as pagC, the genes for both of the Shiga toxins, and the two iron transport system operons fit and chu) was observed. Genes involved in acid resistance and in the SOS response were upregulated. However, genes of the locus of enterocyte effacement or genes involved in peroxide resistance were not differentially expressed. Many genes with putative or unknown functions were upregulated inside human macrophages and may be newly discovered virulence factors. As the Shiga toxin genes were upregulated in macrophages, survival and cytotoxicity assays were performed with isogenic Shiga toxin mutants. The initial uptake of Shiga toxins mutants was higher than that of the wild type; however, the survival rates were significantly lower at 24 h postinfection. Thus, Shiga toxins are implicated in the interaction between E. coli O157:H7 and human macrophages. Understanding the molecular mechanisms used by E. coli to survive within macrophages may help in the identification of targets for new therapeutic agents.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of Montreal, C.P. 6128 Succursale Centre-Ville, Montréal, Québec, Canada H3C 3J7. Phone: (514) 343-7396. Fax: (514) 343-5701. E-mail: france.daigle{at}umontreal.ca

{triangledown} Published ahead of print on 25 August 2008.

Editor: S. R. Blanke

{dagger} Deceased.

Infection and Immunity, November 2008, p. 4814-4822, Vol. 76, No. 11
0019-9567/08/$08.00+0     doi:10.1128/IAI.00446-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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