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Abstract The Gram-negative bacteria, which include Pseudomonas aeruginosa, cause substantialmorbidity and mortality: bacterial pneumonia, septicemia and chronic disease account for ~15% of the totaldeaths in the USA. Therefore, it is imperative that we develop a better cellular and molecularunderstanding of the host interactions with bacterial pathogens, how bacteria avoid or manipulate thehost?s response, and to develop new strategies to prevent disease and improve patient care. For a variety of Gram-negative bacteria, flagellar swimming motility has been demonstrated to berequired to initially infect the host. However, the bacteria must become non-motile to persist during clinicalchronic infection. A well-described example is that the loss of P. aeruginosa motility directly correlates withbacterial persistence, increased bacterial burdens, and increased disease severity in Cystic Fibrosispatients. Our lab was the first to demonstrate that the observed loss of bacterial motility, regardless of lossof flagellar expression, enables P. aeruginosa to evade phagocytic clearance by macrophages andneutrophils both in vitro and in vivo. Additionally, sessile P. aeruginosa, especially upon formation ofmicrocolonies or biofilms, become tolerant to standard-of-care antibiotics: this is reflected in ineffectiveeradication of bacteria from chronically infected patients following antibiotic treatments. These two traits ?phagocytic evasion and antibiotic tolerance ? enable non-motile P. aeruginosa to persist as chronicinfections despite our best current treatments, and thus there is an obvious and pressing need for a novelintervention. Therefore the central goal of this proposal is to elucidate a novel and effective methodologythat will induce the phagocytic clearance of non-motile P. aeruginosa. Our recently published studies thatmechanistically demonstrate that non-motile bacteria avoid triggering the PI3K/Akt-dependent phagocyticresponse identify a potential therapeutic opportunity that guides the central hypothesis of this proposal: thatactivation of the Akt-dependent phagocytic pathway will promote the therapeutic clearance of the non-motile P. aeruginosa that persist in chronic infection. Based on our preliminary data, we propose a single,focused Specific Aim that tests the feasibility of our evidence-supported premise: that we can induce thephagocytic clearance of sessile bacteria. Achievement of this Aim will identify a molecular signalingpathway within host phagocytes, and a methodology by which to induce this pathway, which can potentiallybe harnessed to effect the therapeutic clearance of the non-motile, antibiotic-tolerant bacteria present inchronic infections.

Berwin, Brent L.
Dartmouth College
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