Posters - CONTACT LENS INDUCED PERIPHERAL ULCERATION (CLPU) MAY BE PRODUCED BY ALPHA TOXIN DEFICIENT MUTANT OF S AUREUS AND ITS PARENT STRAIN.

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Posters

November 2001

CONTACT LENS INDUCED PERIPHERAL ULCERATION (CLPU) MAY BE PRODUCED BY ALPHA TOXIN DEFICIENT MUTANT OF S AUREUS AND ITS PARENT STRAIN.

P.Z.J. Wu, E. Hume, A. Thakur, F. Stapleton, M.D.P. Willcox
Cooperative Research Centre for Eye Research and Technology, University of New South Wales, Australia.

Purpose:

S. aureus has been suggested to be responsible for CLPU. However, the pathogenesis of CLPU is not well understood. An animal model of CLPU has been produced in rabbits. The aim of this experiment is to examine the difference of the pathogenicity of an alpha-toxin-deficient mutant and its parent strain, and the role of alpha-toxin in the production of CLPU.

Method:

S. aureus NCTC 8325-4 and its alpha-toxin-deficient mutant DU 1090 were examined for their abilities to produce proteolytic enzymes and hyaluronidase on agar plates with the corresponding substrates. The production of elastase was tested spectrophotometrically using concog-red elastin. Alpha-toxin and beta-toxin production were tested by measuring the bacteria's abilities to cause hemolysis on rabbit and sheep blood respectively. The bacterial strains were then used on rabbits with an artificial corneal epithelial defect, and corneal lesions were produced when the rabbits were allowed to wear contact lens coated with each strain of S. aureus on either eye of the same rabbit. The clinical pictures, bacteriological cultures and histology of the corneal ulceration on both eyes were examined and compared.

Results:

Both strains of S. aureus were found to be able to produce caisinase, gelatinase, hyaluronidase elastase and beta-toxin to the same extent. S. aureus DU1090 caused weak hemolysis to the rabbit red blood cells, while S. aureus 8325-4 causing strong hemolysis, which reflected their difference in alpha-toxin production. Both S. aureus strains may cause corneal ulceration in contact lens wearing eyes. In general, corneal ulceration observed in the eyes wearing DU1090 lens were milder than those seen in the eyes wearing S. aureus 8325-4 coated lenses. S. aureus 8325-4 may cause serious infectious keratitis in the rabbit eyes under the condition in which only CLPU-like lesions were observed with DU1090.

Conclusions:

The enzyme production profile of S. aureus DU 1019 was the same as its parent strain (S. aureus 8325-4). S. aureus strains may produce CLPU-like lesions regardless the presence of alpha-toxin, but the corneal lesions caused by alpha-toxin deficient S. aureus were much milder. S. aureus 8325-4 may cause serious infectious keratitis.

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