Pseudomonas aeruginosa (PA) is one of the two most frequent causes of hospital-acquired pneumonia (HAP), a disease that afflicts 10% of all patients admitted to intensive care units (170). Studies in humans and animal models have shown that the type III secretion system of PA plays an important role in the pathogenesis of infections caused by this bacterium. This system injects four effector proteins into mammalian cells during infection: ExoU, ExoS, ExoT, and ExoY. Our overall objective has been to define the contribution of this system and the individual effector proteins secreted by it to the pathogenesis of acute pneumonia. Our prior studies have demonstrated that secretion of ExoU has the most marked impact on morbidity and mortality in acute pneumonia, both in humans and animal models. Much is known about the molecular and cellular effects of this toxin. For example, it is a phospholipase toxin that causes necrosis following injection into many different mammalian cell types in vitro. Despite this wealth of molecular and cellular knowledge, it remains unclear how PA wields this potent weapon to cause overwhelming infection and death during pneumonia. This proposal will continue our studies utilizing a mouse model to clarify the role of ExoU in the pathogenesis of acute pneumonia and how ExoU secretion results in especially severe pneumonia. Our preliminary data show that whereas ExoU- PA bacteria are rapidly cleared from the lungs over the first 24 hr of infection, ExoU+ bacteria persist in high numbers. We therefore hypothesize that ExoU is targeted to specific cell types during the first 24 hr of infection, which in turn compromises pulmonary defenses and allows PA to persist in the lungs rather than be cleared. Our studies will broadly examine which pulmonary cells are targeted for injection of ExoU but will pay special attention to ExoU interactions with phagocytic cells, since these cells are rapidly recruited to the lungs during this time period and constitute a defensive barrier that must be overcome by any pathogen if it is to persist in the lungs. Such persistence lays the foundation for subsequent tissue injury and the pathophysiological manifestations of pneumonia. The completion of these aims will define the cellular targets of ExoU and whether these phagocytes are killed by ExoU during early acute pneumonia. This information will in turn lay the foundation for future studies designed to block ExoU intoxication, which may lead to therapeutic interventions useful in the treatment or prevention of HAP.

Public Health Relevance

The bacterium Pseudomonas aeruginosa is one of the most frequent causes of pneumonia acquired in the hospital, a disease that has a mortality rate of 30-60%. Our overall objective has been to understand how this bacterium causes severe pneumonia. This information will lay the foundation for therapeutic interventions useful in the treatment of pneumonia.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI053674-09
Application #
8309921
Study Section
Host Interactions with Bacterial Pathogens Study Section (HIBP)
Program Officer
Korpela, Jukka K
Project Start
2002-12-01
Project End
2014-07-31
Budget Start
2012-08-01
Budget End
2014-07-31
Support Year
9
Fiscal Year
2012
Total Cost
$372,627
Indirect Cost
$125,127
Name
Northwestern University at Chicago
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
005436803
City
Chicago
State
IL
Country
United States
Zip Code
60611
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Ozer, Egon A; Morris, Andrew R; Krapp, Fiorella et al. (2016) Draft Genome Sequence of a Multidrug-Resistant Klebsiella quasipneumoniae subsp. similipneumoniae Isolate from a Clinical Source. Genome Announc 4:
Hauser, Alan R; Mecsas, Joan; Moir, Donald T (2016) Beyond Antibiotics: New Therapeutic Approaches for Bacterial Infections. Clin Infect Dis 63:89-95
Tyson, Gregory H; Halavaty, Andrei S; Kim, Hyunjin et al. (2015) A novel phosphatidylinositol 4,5-bisphosphate binding domain mediates plasma membrane localization of ExoU and other patatin-like phospholipases. J Biol Chem 290:2919-37
Zhang, Angelica; Rangel, Stephanie M; Hauser, Alan R (2015) The great escape: Pseudomonas breaks out of the lung. Microb Cell 2:409-411
Rangel, Stephanie M; Diaz, Maureen H; Knoten, Claire A et al. (2015) The Role of ExoS in Dissemination of Pseudomonas aeruginosa during Pneumonia. PLoS Pathog 11:e1004945
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Bowlin, Nicholas O; Williams, John D; Knoten, Claire A et al. (2014) Mutations in the Pseudomonas aeruginosa needle protein gene pscF confer resistance to phenoxyacetamide inhibitors of the type III secretion system. Antimicrob Agents Chemother 58:2211-20
Allen, Jonathan P; Ozer, Egon A; Hauser, Alan R (2014) Different paths to pathogenesis. Trends Microbiol 22:168-9

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