The role of adhesion molecules in the pathogenesis of Staphylococcus aureus keratitis

PURPOSE: We propose that a specific class of adhesins, called "microbial surface components recognizing adhesive matrix molecules" (MSCRAMMs), binding fibronectin and collagen has a critical role in the early events of S. aureus keratitis. METHODS: DNA insertion techniques were used to create site-specific mutants lacking either the MSCRAMM for fibronectin or for type II collagen. New soft contact lenses (Acuvue, VISTAKON) were incubated in a bacterial broth containing one of four strains of S. aureus : fibronectin mutant with its control and collagen mutant with its control. Following incubation, the contaminated lenses were placed onto the de-epithelialized cornea of 12 New Zealand rabbits separated into four experimental groups. Slit -lamp examination and corneal scrapings for culture were performed at 48 hours, and corneas were removed for histologic examination. RESULTS: 33% of fibronectin mutants were infected, while 67% of the control rabbits were infected. None of the type II collagen mutants developed keratitis, while 67% of the control rabbits exhibited infection. Cultures on blood agar and histopathologic examination confirmed bacterial infection in clinically suspected cases. DISCUSSION: MSCRAMMs binding either fibronectin or collagen are involved in the development of experimental microbial keratitis.