Failure of intravitreal dexamethasone to diminish inflammation or retinal toxicity in an experimental model of Bacillus cereus endophthalmitis.
OBJECTIVE
To determine whether the usual clinical dose of intravitreal dexamethasone can attenuate intraocular inflammation and retinal necrosis in a rabbit model of fulminant Bacillus cereus endophthalmitis induced by crude exotoxins.


METHODS
Thirty-six eyes from pigmented mongrel rabbits received intravitreal injections of varying concentrations of crude B. cereus exotoxins with or without concomitant injections of 400 microg of dexamethasone sodium phosphate (0.1% solution). After ophthalmoscopic examination at 4 or 18 hr postinjection, the animals were killed and histopathologic findings graded.


RESULTS
Intraocular inflammation and retinal necrosis scores in eyes receiving both exotoxins and dexamethasone did not differ significantly from eyes receiving exotoxins alone for any exotoxin dose at 4 or 18 hr. The severity of retinal necrosis increased with toxin dose and was nearly maximal after 4 hr. Intraocular inflammation also generally increased with dose, but continued to increase until 18 hr.


CONCLUSIONS
Standard clinical doses of intravitreal dexamethasone do not appear to attenuate the intraocular inflammatory or tissue response to secreted B. cereus exotoxins. Other treatment modalities including vitrectomy, to decrease exotoxin load, and exotoxin inhibitors may be necessary for the effective treatment of B. cereus endophthalmitis.
Pollack
John S
JS
Illinois Retina Associates S.C., Chicago, Illinois, USA.
Beecher
Douglas J
DJ
Pulido
Jose S
JS
Lee Wong
Amy C
AC
D000818:Animals; D001409:Bacillus cereus / Q000502:physiology*; D003907:Dexamethasone / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D004195:Disease Models, Animal; D009877:Endophthalmitis / Q000382:microbiology / Q000517:prevention & control*; D015818:Eye Infections, Bacterial / Q000382:microbiology / Q000517:prevention & control*; D005938:Glucocorticoids / Q000008:administration & dosage*; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology / Q000517:prevention & control*; D007249:Inflammation / Q000517:prevention & control; D007267:Injections; D009336:Necrosis; D011817:Rabbits; D012160:Retina / Q000187:drug effects* / Q000473:pathology; D014822:Vitreous Body
D005938:Glucocorticoids; C004180:dexamethasone 21-phosphate; D003907:Dexamethasone