Search

Purpose: To determine the effect of age on the extent of pathogenesis of Staphylococcus keratitis in the mouse., Methods: Corneas of young and aged mice (BALB/c, A/J, and C57BL/6) were scarified and topically inoculated with S. aureus. Slit lamp examination (SLE) and histopathology were performed, and bacterial colony forming units and myeloperoxidase activity were determined., Results: SLE scores of infected eyes of aged mice were significantly higher at days 1 and 3 postinfection (PI) as compared to infected young mice. Histopathological changes observed in all aged mice were more severe than those in young mice. Young BALB/c and A/J mice demonstrated minimal signs of keratitis by day 3 PI, whereas aged mice of both strains demonstrated severe keratitis by day 3. Young C57BL/6 mice showed no clinical signs of keratitis, whereas aged C57BL/6 mice demonstrated moderate keratitis., Conclusions: Aged mice with S. aureus keratitis demonstrated increased pathology as compared to young mice.

Purpose: To determine the effectiveness of lysostaphin treatment of experimental endophthalmitis caused by methicillin-resistant Staphylococcus aureus (MRSA)., Methods: In one experiment, rabbits were injected in the mid-vitreous with 50 or 200 CFU of S. aureus; untreated groups and groups injected intra-vitreally at 8 or 24 hours postinfection with vehicle or lysostaphin (0.1 mg/ml) were compared in terms of CFU/ml vitreous at 24 or 48 hours postinfection. Histopathology of untreated and treated eyes was also compared. To quantify the potency of lysostaphin, additional rabbits were injected with 50 CFU of S. aureus and untreated eyes and eyes treated at 8 hours with 0.001, 0.01 or 0.05 mg/ml were compared in terms of CFU/ml vitreous at 24 hours postinfection., Results: Vitreous of untreated eyes or vehicle-treated eyes injected with 50 or 200 CFU of S. aureus contained 5-10 million CFU/ml at 24 or 48 hours postinfection. All eyes treated with lysostaphin at 8 hours postinfection had less than 1 log CFU/ml in the vitreous (P >or= 0.0001). Similarly, eyes treated with lysostaphin at 24 hours postinfection had approximately 1 log of CFU/ml at 48 hours postinfection. None of the untreated eyes were sterile and 88% or 50% of the eyes treated at 8 or 24 hours postinfection, respectively, were sterile. Eyes treated with lysostaphin at 8, but not 24, hours postinfection had less pronounced pathologic changes than the untreated eyes (P = 0.002). A significant reduction in the CFU/ml vitreous at 24 hours postinfection was obtained by treating infected eyes at 8 hours postinfection with lysostaphin at concentrations of >or=0.001 mg/ml (P

Purpose: Previous studies from this laboratory have demonstrated, in a rabbit model of keratitis, a relationship between the corneal virulence of Staphylococcus aureus and the alpha-toxin activity of the infecting bacteria. This study is a histopathological characterization of the action of purified alpha-toxin on corneal tissue., Methods: Alpha-toxin was purified by isoelectric focusing and intrastromally injected into rabbit corneas (2 micrograms per cornea). A kinetic analysis of toxin effect was performed following injection. Normal corneas and corneas injected with phosphate buffered saline (PBS) or heat-inactivated alpha-toxin in PBS served as controls. Eyes were examined from 0 to 4 h by slit lamp examination (SLE) and scored on the basis of seven ocular parameters. Corneal tissue was removed and examined for histopathological changes., Results: From 0.5 to 4 h post-injection, alpha-toxin injection induced a significant increase in the SLE score relative to untreated eyes or eyes injected with PBS (P < 0.0001). Histolo-pathological examination of corneas one-half h after alpha-toxin injection revealed edema of the central cornea and death of epithelial cells by both necrosis and apoptosis. Later times showed continued edema and loss of apparently normal epithelial cells. Development of polymorphonuclear (PMN) leukocyte infiltration from the tear film into the central cornea and from limbal vessels into the peripheral cornea was observed., Conclusions: Purified alpha-toxin mediates cell death by necrosis and apoptosis, sloughing of viable corneal epithelial cells, severe corneal edema, and PMN migration into the cornea from both the tear film and limbal vessels. The pathologic changes revealed by histological studies of corneas injected with purified alpha-toxin included death of cells by necrosis and apoptosis as well as overall changes analogous to that seen by SLE of eyes infected with wild-type, but not alpha-toxin-deficient strains of Staphylococcus aureus.