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Emma B. H. Hume, Joseph J. Dajcs, Judy M. Moreau, Gregory D. Sloop, Mark D. P. Willcox, Richard J. O’Callaghan; Staphylococcus Corneal Virulence in a New Topical Model of Infection. Invest. Ophthalmol. Vis. Sci. 2001;42(12):2904-2908.
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© ARVO (1962-2015); The Authors (2016-present)
purpose. To develop a topical inoculation model of Staphylococcus
aureus keratitis in which scarification, contact lenses, and
spermidine are used to inhibit the host defenses and to investigate the
role of α-toxin in this infection.
methods. An α-toxin–positive parent strain (8325-4), its isogenicα
-toxin–negative mutant (DU1090), and a genetically rescued form of
the mutant (DU1090/pDU1212) were bound to rabbit-specific contact
lenses, treated with spermidine (50 mM), and applied to scarified
rabbit corneas. Eyes were treated topically with spermidine before and
after lens application. Eyes were graded for disease by slit lamp
examination (SLE) every 6 hours until 24 hours PI (PI), and erosion
diameters were measured. Histopathologic changes and colony forming
units (CFUs) of bacteria were determined.
results. Spermidine treatment and inoculation of eyes with Staphylococcus on contact lenses resulted in significant
increases in both CFUs per cornea (P = 0.0041) and
SLE score (P ≤ 0.0001), compared with eyes
inoculated without spermidine treatment. The CFUs in eyes infected with
8325-4, DU1090, or DU1090/pDU1212 demonstrated a similar
(P ≥ 0.1959) multilog increase in CFUs over the
inoculum at 24 hours PI. The α-toxin–producing strains, 8325-4 and
DU1090/pDU1212, caused significantly more disease than theα
-toxin–deficient mutant DU1090 at 24 hours PI
(P ≤ 0.0001). Histopathology revealed bacteria in
scarified regions of the corneas and, for 8325-4 and DU1090/pDU1212,
extensive epithelial sloughing and severe inflammation.
conclusions. A new topical model of infection has been developed, and α-toxin is
an important virulence factor in this model.
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