Nancy Freitag

Professor

Ph.D., University of California at Los Angeles

Room 8053 COMRB, Tel: 312-355-4903

Our lab's research is focused on understanding how pathogens make themselves at home within human and animal cells, and to discover the mechanisms used by mammalian cells to fight off pathogenic intruders.

Listeria monocytogenes as an important food-borne pathogen and a model system for the study of intracellular infections

Listeria monocytogenes is an important agent of food-borne infections and has been responsible for some of the most extensive and expensive food recalls.  This bacterium is a ubiquitous environmental bacterium that can survive in the soil as a saprophyte, but which maintains an ability to invade and replicate within the cells of susceptible humans and animals.  While environmental microorganisms are numerous, relatively few have the capacity to cause human disease, thus we are interested in how L. monocytogenes balances its life as an environmental organism with the lifestyle of a human/animal pathogen.


Our studies take advantage of the fact that L. monocytogenes is very amenable to genetic manipulation, and that excellent cell culture and animal infections models exist to study the molecular mechanisms of bacterial pathogenesis.  Current work is focused on defining the role of small bacterial peptide signaling molecules in promoting L. monocytogenes intracellular replication, and on the mechanisms of virulence factor secretion.  L. monocytogenes appears to maintain its virulence arsenal by exploiting secreted factors for a variety of activities.  For example, a secreted bacterial chitinase that functions to break down chitin in the outside environment also suppresses the expression of host innate immune responses that normally help to limit bacterial infection.


We are also interested in determining what contributes to host tissue tropism during bacterial infection.  L. monocytogenes has been well associated with infections of the central nervous system and with fetal infections during pregnancy, but we have recently found that some clinical isolates also have the capacity to cause cardiac infections.  We are therefore working to define which bacterial factors define where and how L. monocytogenes chooses to replicate within an infected host.  Preliminary experiments suggest that the bacterium may manipulate host cell metabolism to improve intracellular bacterial replication.

 

Defining the impact of anesthesia on host susceptibility to microbial infection.

Additional studies in the lab are exploring how common anesthetic agents increase host susceptibility to microbial infection. Infections acquired following surgical procedures account for billions of dollars in health care costs and have severe negative impact on patient outcomes. We are currently using models of Staphylococcus aureus and Klebsiella pneumoniae infection in addition to L. monocytogenes to decipher how anesthetic agents influence host immune responses and to develop new strategies to limit hospital acquired infections.