Staphylococcus Alpha-Toxin Action on the Rabbit Iris: Toxic Effects and Their Inhibition

Abstract

Purpose: Staphylococcus aureus infection of the anterior chamber can occur after cataract surgery, causing inflammation and extensive damage to the iris. Alpha-toxin, the most potent S. aureus corneal toxin, was tested as a possible mediator of damage to the iris, and alpha-toxin anti-serum and a chemical toxin inhibitor were tested as potential pathology-reducing agents.

Methods: The hemolytic activity of alpha-toxin and its inhibition by a chemical inhibitor or anti-serum were quantified in vitro. Purified alpha-toxin, heat-inactivated toxin, or alpha-toxin plus normal serum, alpha-toxin anti-serum, or the chemical inhibitor, methyl-β-cyclodextrin-cholesterol (CD-cholesterol), was injected into the rabbit anterior chamber. Pathological changes were photographed, quantified by slit-lamp examination (SLE) scoring, and further documented by histopathological analysis.

Results: At five hours post-injection, eyes injected with alpha-toxin or heat-inactivated toxin had a mean SLE score of 7.3 ± 0.59 or 0.84 ± 0.19, respectively. Active toxin caused moderate to severe iris edema, severe erosion of the iris, and mild to moderate fibrin accumulation in the anterior chamber. Alpha-toxin plus anti-serum or CD-cholesterol, in contrast to alpha-toxin alone, caused less iris edema and epithelium sloughing as well as significantly lower SLE scores than eyes receiving alpha-toxin alone (p ≤ 0.019).

Conclusion: Alpha-toxin caused extensive iris damage and inflammation, and either anti-alpha-toxin anti-serum or CD-cholesterol was able to significantly reduce toxin-mediated damage and inflammation.

• Alpha-toxin
• anterior chamber
• iris
• Staphylococcus aureus, toxin inhibitor

ACKNOWLEDGEMENTS

The authors wish to thank Dr. Mary Marquart and Dr. Anna Mathew for their review of this study.

DECLARATION OF INTEREST

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. This work was supported by NEI Grant EY010974.