Assessment of the role of gamma-toxin in experimental endophthalmitis using a hlg-deficient mutant of Staphylococcus aureus.

Purified gamma-toxin is known to have a proinflammatory effect in the rabbit vitreous humor. To assess the biological role of the gamma-toxin, when expressed in vivo by Staphylococcus aureus strain Newman, the vitreous humor of rabbit eye was used as an infection model. A gamma-toxin-deficient mutant of strain Newman was constructed by allelic replacement. S. aureus Newman wild-type, its hlg-deficient derivative strain (N65) and the strain N65 complemented with the wild-type hlg+ gene were injected into the vitreous humor of rabbit eye. All three strains produced a strong proinflammatory effect in the eye conjunctiva, posterior and anterior chambers, suggesting a role for another unidentified proinflammatory component of strain Newman distinct from the gamma-toxin. These components are not the leucocidin of Panton-Valentine, beta-toxin or alpha-toxin which are not produced by this strain. Only the hlg-deficient mutant lacked the ability to cause inflammation in the eyelid, whereas the two Hlg-producing strains gave strong inflammation. These data suggest that in vivo, strain Newman produces as yet unidentified proinflammatory molecules and that the in vivo-produced HlgA, HlgB and HlgC molecules expressed by the gamma-toxin locus, contribute in part to the inflammatory process observed in vivo in the rabbit eye.