The effect of steroids on the intraocular toxicity of Bacillus cereus exotoxins

Purpose. To determine whether intraocular steroids attenuate the intraocular reaction to exotoxins elaborated by Bacillus cereus. Methods. Fifteen pigmented mongrel rabbit eyes received intraocular injections of varying concentrations of crude B. cereus exotoxins with or without concomitant injections of 400 μg of dexamethasone and the animals were then sacrificed. The ophthalmoscopic and histopathologic responses were then graded as previously described (Infect Immun 63:632-639, 1995). Results. At 4 hours the ophthalmoscopic examination showed little difference between those eyes with and without dexamethasone. The eyes that had higher doses of toxin had worse inflammation. Histologically even at the lowest dose of B. cereus toxin the steroid treated eyes showed no statistical difference from the untreated eyes. Mean histologic grade in low dose toxin eyes was .80±.81 vs. .99±.73 for eyes with steroids. At higher doses again no statistically significant difference was noted. Conclusions. Steroids do not appear to attenuate the tissue response to extracted B. cereus exotoxins. Other treatment modalities including vitrectomy to decrease exotoxin load and possibly exotoxin inhibitors may be useful in the treatment of established B. cereus endophthalmitis.