Bacterial infections of the eye can have vision-threatening complications and often are associated with prosthetic devices such as contact lenses, scleral buckles, and intraocular lenses. Pseudomonas aeruginosa (PA) is one of the most common causes of bacterial keratitis. The central hypothesis of this proposal is that biofilm formation plays an important role in the pathogenesis of ocular infections of PA and that an understanding of the biology and genetics of Pseudomonas aeruginosa biofilm formation will have relevance to the development of novel antimicrobial therapies. Bacteria grow as planktonic (or free-living) cells or as surface-attached communities known as biofilms. Biofilm formation contributes to the pathogenesis of many clinical infections associated with prosthetic devices by allowing bacteria to persist on abiotic surfaces which come in contact with the body, by facilitating colonization of biotic surfaces and by rendering bacteria more resistant to antimicrobial agents. However, the relevance of biofilm formation to ocular infections has not been extensively studied. Bacterial keratitis caused by PA will be the model system studied in this project. Existing biofilm mutants of PA, as well as additional mutants that will be developed in the course of the project, will be used to elucidate the biology and genetics related to PA biofilm formation on abiotic and biotic surfaces relevant to the eye. The functions mutated in these strains may define novel drug targets. In addition, inhibitor studies may identify new classes of compounds that prevent and/or eliminate eye infections. The ability of growth in a biofilm to render PA resistant to the innate immune system, specifically the human B-defensin (hBD) 1 and 2 will be investigated. hBD 1 and 2 are recently described antimicrobial peptides secreted by the corneal and conjunctival epithelium. hBD 1 and 2 are active against PA under planktonic conditions, but have not been tested against organisms growing in a biofilm. If biofilm-based resistance exists, it would presumably contribute to keratitis and identification of genes that play a role in this process may be novel targets for rendering biofilm bacteria sensitive to antibiotics and defensins. If biofilm and planktonic cells are as equally sensitive to hBD-l and hBD-2, this would suggest that B-defensins can bypass biofilm-specific biocide resistance, and furthermore, these compounds (or derivatives) might make excellent therapeutics to prevent and/or treat biofilm-based infections.

National Institute of Health (NIH)
National Eye Institute (NEI)
Clinical Investigator Award (CIA) (K08)
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Study Section
Special Emphasis Panel (ZEY1-VSN (02))
Program Officer
Shen, Grace L
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Dartmouth College
Schools of Medicine
United States
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Siedlecki, Andrew N; Tapp, Stephanie; Tosteson, Anna N A et al. (2016) Surgery Versus Interferon Alpha-2b Treatment Strategies for Ocular Surface Squamous Neoplasia: A Literature-Based Decision Analysis. Cornea 35:613-8
Zegans, Michael E; Wagner, Jeffrey C; Cady, Kyle C et al. (2009) Interaction between bacteriophage DMS3 and host CRISPR region inhibits group behaviors of Pseudomonas aeruginosa. J Bacteriol 191:210-9
Toutain-Kidd, Christine M; Kadivar, Samoneh C; Bramante, Carolyn T et al. (2009) Polysorbate 80 inhibition of Pseudomonas aeruginosa biofilm formation and its cleavage by the secreted lipase LipA. Antimicrob Agents Chemother 53:136-45
Zegans, Michael E; Sanchez, Paul A; Likosky, Donald S et al. (2009) Clinical features, outcomes, and costs of a conjunctivitis outbreak caused by the ST448 strain of Streptococcus pneumoniae. Cornea 28:503-9
Srinivasan, M; Lalitha, P; Mahalakshmi, R et al. (2009) Corticosteroids for bacterial corneal ulcers. Br J Ophthalmol 93:198-202
Kirn, Thomas J; Levy, Norman B; Gosselin, J J Benoit et al. (2007) Peripheral T-cell lymphoma presenting as sclerouveitis. Cornea 26:1147-9
Toutain, Christine M; Caizza, Nicky C; Zegans, Michael E et al. (2007) Roles for flagellar stators in biofilm formation by Pseudomonas aeruginosa. Res Microbiol 158:471-7
Takemori, Nobuaki; Komori, Naoka; Matsumoto, Hiroyuki (2006) Highly sensitive multistage mass spectrometry enables small-scale analysis of protein glycosylation from two-dimensional polyacrylamide gels. Electrophoresis 27:1394-406
Toutain, Christine M; Zegans, Michael E; O'Toole, George A (2005) Evidence for two flagellar stators and their role in the motility of Pseudomonas aeruginosa. J Bacteriol 187:771-7
Becker, Heidi I; Walton, R Christopher; Diamant, Jonathan I et al. (2004) Anterior uveitis and concurrent allergic conjunctivitis associated with long-term use of topical 0.2% brimonidine tartrate. Arch Ophthalmol 122:1063-6

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