Research in my laboratory focuses on the pathogenesis of bacterial infections of the cornea. The principal aim of my research is
to determine why patients who wear contact lenses are prone to infectious keratitis. These infections most often involve the bacterium
Pseudomonas aeruginosa and can lead to severe vision loss. The results of initial studies indicated that ocular flora is altered in
some contact lens wearers and that a large proportion of patients' lens cases are contaminated with bacteria during normal use.
However, neither of these phenomena entirely explain the pathogenesis of infection, since in general bacteria cannot infect a healthy
cornea, even when introduced in large numbers. This implies that there must be some form of compromise, in addition to bacterial
contamination of the eye before the infectious process can begin. For this reason we are interested in establishing how the healthy
cornea resists infection, how contact lens wear and other predisposing factors could compromise these defenses, and what bacterial
virulence factors are involved in initiating infection. This project involves the study of bacterial interaction with tear film factors
and the ocular surface, bacterial adherence to cornea and contact lenses, mechanisms of bacterial invasion and killing of corneal
epithelial cells, transcorneal migration of bacteria and disruption of normal host tissue physiology by bacteria.
It is widely believed that in the healthy eye infection is prevented because tear film factors are able to neutralize bacteria, and
that bacteria are not able to adhere to the cornea unless it is overtly injured. However, the results of our studies have demonstrated
that neither of these assumptions are entirely accurate. We have found that P. aeruginosa can survive for several hours in tears, and
that this microbe can adhere to uninjured cornea, under certain circumstances. Other findings are that ocular mucin and the cell surface
glycocalyx protect the cornea from infection by inhibiting bacterial adherence to underlying corneal epithelial cells, that contact lens
wear increases bacterial adherence to corneal epithelial cells, and that P. aeruginosa - which is thought to be an extracellular pathogen
- is in fact able to invade corneal epithelial cells. In addition to characterizing corneal defenses and the events that occur during
infection, we are also studying the molecular mechanisms involved in these processes with a view to developing therapeutic and/or
preventative measures.
Techniques that are being used to study bacterium/host interactions include adherence assays, bacterial invasion and cytotoxicity
assays, microscopy (including light, fluorescence, immunohistochemistry, scanning and transmission electron microscopy), various
biochemical assays and molecular genetics. Although much of this work is performed using primary epithelial cell cultures, we have
developed several other models for these studies. These include in vitro models for the study of bacterial interaction with human
corneal cells and whole cornea of rat, rabbit and mouse, and an in vivo model for infection in mice.
Zolfaghar I, Angus AA, Kang PJ, To A, Evans DJ, Fleiszig SM. Mutation of retS, encoding a putative hybrid two-component regulatory protein in Pseudomonas aeruginosa, attenuates multiple virulence mechanisms. Microb. Infect. 2005 Oct;7(13):1305-16. Epub 2005 Jun 13.
Cowell BA, Evans DJ, Fleiszig SM. Actin cytoskeleton disruption by ExoY and its effects on Pseudomonas aeruginosa invasion. FEMS Microbiol Lett. 2005 Sep 1;250(1):71-6.
McNamara NA, Andika R, Kwong M, Sack RA, Fleiszig SM. Interaction of Pseudomonas aeruginosa with human tear fluid components. Curr Eye Res. 2005 Jul;30(7):517-25.
Ni M, Evans DJ, Hawgood S, Anders EM, Sack RA, Fleiszig SM. Surfactant protein D is present in human tear fluid and the cornea and inhibits epithelial cell invasion by Pseudomonas aeruginosa. Infect Immun. 2005 Apr;73(4):2147-56.
Lee EJ, Evans DJ, Fleiszig SM. Role of Pseudomonas aeruginosa ExsA in penetration through corneal epithelium in a novel in vivo model. Invest Ophthalmol Vis Sci. 2003 Dec;44(12):5220-7.
Lee EJ, Truong TN, Mendoza MN, Fleiszig SM. A comparison of invasive and cytotoxic Pseudomonas aeruginosa strain-induced corneal disease responses to therapeutics. Curr Eye Res. 2003 Nov;27(5):289-99.
Zolfaghar I, Evans DJ, Fleiszig SM. Twitching motility contributes to the role of pili in corneal infection caused by Pseudomonas aeruginosa. Infect Immun. 2003 Sep;71(9):5389-93.
Lee EJ, Cowell BA, Evans DJ, Fleiszig SM. Contribution of ExsA-regulated factors to corneal infection by cytotoxic and invasive Pseudomonas aeruginosa in a murine scarification model. Invest Ophthalmol Vis Sci. 2003 Sep;44(9):3892-8.
Cowell BA, Twining SS, Hobden JA, Kwong MS, Fleiszig SM. Mutation of lasA and lasB reduces Pseudomonas aeruginosa invasion of epithelial cells. Microbiology. 2003 Aug;149(Pt 8):2291-9.
Fleiszig SM, Kwong MS, Evans DJ. Modification of Pseudomonas aeruginosa interactions with corneal epithelial cells by human tear fluid. Infect Immun. 2003 Jul;71(7):3866-74.
Cowell BA, Weissman BA, Yeung KK, Johnson L, Ho S, Van R, Bruckner D, Mondino B, Fleiszig SM. Phenotype of Pseudomonas aeruginosa isolates causing corneal infection between 1997 and 2000. Cornea. 2003 Mar;22(2):131-4.
Fleiszig SM, Evans DJ. Contact lens infections: can they ever be eradicated? Eye Contact Lens. 2003 Jan;29(1 Suppl):S67-71; discussion S83-4, S192-4.
Evans DJ, Kuo TC, Kwong M, Van R, Fleiszig, SMJ. Mutation of csk, encoding the C-terminal Src kinase, reduces Pseudomonas aeruginosa internalization by mammalian cells and enhances bacterial cytotoxicity. Microbial Pathogenesis, 2002: 33; 135-43.
Fleiszig SM, Evans DJ. The pathogenesis of bacterial keratitis: studies with Pseudomonas aeruginosa. Clin Exp Optom. 2002 Sep;85(5):271-8. Review.
Evans D, Kuo T, Kwong M, Van R, Fleiszig S. Pseudomonas aeruginosa strains with lipopolysaccharide defects exhibit reduced intracellular viability after invasion of corneal epithelial cells. Exp Eye Res. 2002 Dec;75(6):635-43.
Evans DJ, Maltseva IA, Wu J, Fleiszig SMJ. Pseudomonas aeruginosa internalization by corneal epithelial cells involves MEK and ERK signal transduction proteins. FEMS Microbiology Letters, 2002: 213; 73-9.
Srinivas SP, Mutharasan R, Fleiszig S. Shear-induced ATP release by cultured rabbit corneal epithelial cells. Adv Exp Med Biol. 2002;506(Pt A):677-85.
Fleiszig SMJ, McNamara NA, Evans DJ. The tear film and defense against infection. Adv Exp Med Biol 506: 523-530, 2002.
Fleiszig SMJ, Arora SK, Van R, Ramphal R. FlhA, a component of the flagellum assembly apparatus of Pseudomonas aeruginosa, plays a role in internalization by corneal epithelial cells. Immun 69:4931-4937, 2001.
Lakkis C, and Fleiszig SMJ. Resistance of Pseudomonas aeruginosa isolates to hydorgel contact lens disinfection correlates with cytotoxic activity. J. Clin Microbiol. 39: 1477-1486, 2001.
Cowell BA, Chen DY, Frank DW, Vallis AJ, Fleiszig SM. ExoT of cytotoxic Pseudomonas aeruginosa prevents uptake by corneal epithelial cells. Infect Immun. 2000 Jan;68(1):403-6.
McNamara NA, Sack RA, Fleiszig SM. Mucin-bacterial binding assays. Methods Mol Biol. 2000;125:429-37. Review.
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