The intestine of animals is colonized by a large number of commensal microorganisms that contribute to many host physiological processes. An important role of the intestinal microbiota is to protect the host against colonization and invasio by pathogens that often enter the intestinal tract. However, the interaction between the microbiota and the host immune system that mediates protection against enteric pathogens remains poorly understood. Furthermore, the mechanisms that enteric pathogens employ to overcome the presence of the microbiota remain poorly understood. We find that the commensal microbiota is critical for the elimination of Citrobacter rodentium, an enteric mouse pathogen that models human infection by diarrheagenic enterohemorrhagic (EHEC) and enteropathogenic (EPEC) Escherichia coli. EHEC and EPEC are important causes of watery diarrhea and mortality worldwide. These Gram-negative bacteria are food- and waterborne non-invasive pathogens which attach to and colonize the intestinal tract by inducing characteristic attaching- and-effacing (A/E) lesions on the intestinal epithelium, leading to transient enteritis r colitis in humans. The genome of EPEC and EPEC and related pathogens harbor the locus for enterocyte effacement (LEE) which is critical for bacterial colonization and the ability to cause pathology. LEE virulence factors are controlled by Ler, a transcription factor that acts as a globa regulator of LEE virulence genes. We plan in this proposal to use the Citrobacter rodentium model to test several hypotheses raised by our Preliminary Results. The goal of this proposal is to gain a better understanding of the interactions among the pathogen, the host immune system and the indigenous microbiota that are critical in controlling the colonization and eradication of enteric pathogens. In addition, we propose to develop novel therapeutic strategies to treat C. rodentium-induced colitis based on the ability of the indigenous microbiota to outcompete the pathogen with reduced Ler-mediated virulence. Given that A/E pathogens are a major cause of death and morbidity in human populations, this proposal is expected to have a significant and broad impact in the medical field

Public Health Relevance

The intestine of animals is colonized by a large number of commensal microorganisms that play an important role in protection against enteric bacterial pathogens, but the mechanisms involved remain poorly understood. The goal of this proposal is to gain a better understanding of the interactions among the enteric pathogen C. rodentium, the host immune system and the intestinal microbiota that regulate the colonization and clearance of the pathogen.

Agency
National Institute of Health (NIH)
Type
Research Project (R01)
Project #
5R01DK095782-02
Application #
8662258
Study Section
Gastrointestinal Mucosal Pathobiology Study Section (GMPB)
Program Officer
Perrin, Peter J
Project Start
Project End
Budget Start
Budget End
Support Year
2
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Pathology
Type
Schools of Medicine
DUNS #
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
De la Fuente, Marjorie; Franchi, Luigi; Araya, Daniela et al. (2014) Escherichia coli isolates from inflammatory bowel diseases patients survive in macrophages and activate NLRP3 inflammasome. Int J Med Microbiol 304:384-92
Kamada, Nobuhiko; Núñez, Gabriel (2014) Regulation of the immune system by the resident intestinal bacteria. Gastroenterology 146:1477-88