Timing of dexamethasone treatment in experimental Staphylococcus aureus endophthalmitis.
OBJECTIVE
This study sought to determine whether intravitreal dexamethasone with vancomycin preserves retinal function in eyes with experimental Staphylococcus aureus endophthalmitis better than intravitreal vancomycin alone.


METHODS
Twenty-four rabbits received intravitreal injections in both eyes with S. aureus. Right eyes were treated with intravitreal dexamethasone plus vancomycin and left eyes were treated with vancomycin alone at 24, 36, 48, or 72 hours after inoculation. Evaluation was performed by slit-lamp biomicroscopy, indirect ophthalmoscopy, and electroretinogram. Vitreous humor cultures and histopathologic examinations were performed on the eyes after the rabbits were killed.


RESULTS
The combination of intravitreal dexamethasone and vancomycin resulted in significantly less inflammation than vancomycin alone at 24 and 36 hours after inoculation, but electroretinograms showed significantly better preservation only at 36 hours after bacterial inoculation. Viable bacteria were cultured from eyes treated 48 and 72 hours after inoculation.


CONCLUSIONS
Intravitreal dexamethasone was found to be beneficial by electroretinography when administered 36 hours after infection. In the authors' model, a single intravitreal injection of vancomycin with or without the addition of dexamethasone was insufficient to sterilize eyes 48 and 72 hours after bacterial inoculation.
Yoshizumi
M O
MO
Jules Stein Eye Institute, UCLA School of Medicine, Department of Ophthalmology 90095-7000, USA.
Lee
G C
GC
Equi
R A
RA
Kim
I T
IT
Pitchekian-Halabi
H
H
Adamu
S A
SA
Mondino
B J
BJ
D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D003907:Dexamethasone / Q000008:administration & dosage* / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D004596:Electroretinography; D009877:Endophthalmitis / Q000188:drug therapy* / Q000382:microbiology*; D007267:Injections; D009887:Ophthalmoscopy; D011817:Rabbits; D013203:Staphylococcal Infections; D013211:Staphylococcus aureus; D013997:Time Factors; D014640:Vancomycin / Q000627:therapeutic use; D014822:Vitreous Body
D000900:Anti-Bacterial Agents; D000893:Anti-Inflammatory Agents; D014640:Vancomycin; D003907:Dexamethasone