From Soil to Cytosol: The Pathogenic Transition of the Environmental Bacterium Listeria Monocytogenes

Hosted by: Dr. Darren Higgins

Speaker: Nancy Freitag, University of Illinois at Chicago

Harvard Medical School, Warren Alpert Building, 341, 200 Longwood Avenue, Boston, MA.

From her web page:

Themes

•Regulation of bacterial virulence gene expression within host cells

•Host responses to bacterial infection

•Pathogen survival within host cells

Accomplishments

•Identified key regulatory switches used by the bacteria to makes themselves at home within human cells. These switches must be engaged at the proper time to promote bacterial infection.

•Isolated bacterial mutants that ‘think’ they are inside of host cells. These mutants produce proteins in broth culture that are normally only made within infected cells. We are beginning to identify these proteins and discover their functional roles in disease.

•Developed a new host system that will allow us to explore early host defenses to Listeria infection. Surprisingly, the common fruit fly fights off bacterial infection using many of the same defenses as human cells. We can explore and identify defensive strategies in the fly and then look for their counterparts in humans.

These accomplishments will be useful for:

•Improved diagnostics. L. monocytogenes looks very different when it’s inside vs. outside of host cells. Improved food detection strategies must be designed to recognize intracellular and extracellular bacteria.

•Improved therapies. Significant mortality occurs in patients with listeriosis even with antibiotic therapy. By defining the spectrum of host defenses used to fight bacterial infection, we may be able to develop ways of improving those defenses and strengthening the host attack.

•Insights into host survival strategies for other pathogens.