May 2006
Volume 47, Issue 13
ARVO Annual Meeting Abstract  |   May 2006
Alpha–Toxin Susceptibility Impacts Age–Related Differences in Experimental S. aureus Keratitis
Author Affiliations & Notes
  • K.S. Monds
    Microbiology, UMC, Jackson, MS
    Microbiology, Immunology, and Parasitology, LSU Health Sciences Center, New Orleans, LA
  • M.E. Marquart
    Microbiology, UMC, Jackson, MS
  • J.M. Reed
    Microbiology, UMC, Jackson, MS
  • A.R. Caballero
    Microbiology, UMC, Jackson, MS
  • R.J. O'Callaghan
    Microbiology, UMC, Jackson, MS
  • Footnotes
    Commercial Relationships  K.S. Monds, None; M.E. Marquart, None; J.M. Reed, None; A.R. Caballero, None; R.J. O'Callaghan, None.
  • Footnotes
    Support  NEI Grant EY10974
Investigative Ophthalmology & Visual Science May 2006, Vol.47, 1883. doi:
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      K.S. Monds, M.E. Marquart, J.M. Reed, A.R. Caballero, R.J. O'Callaghan; Alpha–Toxin Susceptibility Impacts Age–Related Differences in Experimental S. aureus Keratitis . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1883.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : Define and analyze age–related changes in susceptibility to experimental keratitis

Methods: : Intrastromal injections of 100 colony–forming units (CFU) of S. aureus strain 8325–4 were used to induce keratitis in young (8 – 10 weeks) and aged (approximately 36 months) New Zealand white rabbits (n = 6 corneas per group). Purified staphylococcal alpha–toxin (0.37 µg; 25.6 hemolytic units) was intrastromally injected into corneas of both young and aged rabbits (n = 6 corneas per group). Pathology was scored by two masked observers based on gross and slit–lamp examinations at 15, 20, and 25 hours post–infection, and at 1 and 3 hours following injection of toxin. Additionally, alpha–toxin–mediated hemolytic assays were performed using erythrocytes obtained from young and aged rabbits.

Results: : Slit–lamp examinations of pathology due to S. aureus keratitis produced scores significantly lower in aged than in young animals at 15, 20, and 25 hours post–infection (P ≤ 0.001). Log CFU’s were not significantly different between young and aged animals at the time of sacrifice (25 hours post–infection; P = 0.896). Intrastromal injection of purified alpha–toxin demonstrated significantly more pathology in young, as compared to aged, rabbit corneas (P ≤ 0.0005). Hemolysis assays revealed that erythrocytes of young rabbits were four–fold more susceptible to the action of staphylococcal alpha–toxin than those of their aged counterparts.

Conclusions: : Corneas and erythrocytes of aged rabbits, relative to those of young rabbits, were significantly less susceptible to S. aureus keratitis and to alpha–toxin; this difference likely being mediated by decreased response to the action of alpha–toxin.

Keywords: aging • keratitis • Staphylococcus 

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