Intravitreal vancomycin and amikacin versus intravenous imipenem in the treatment of experimental Staphylococcus aureus endophthalmitis.

BACKGROUND

Controversy still surrounds the intravenous (IV) treatment of endophthalmitis. The purpose of this study was to compare IV and intraocular (IO) treatment in experimental Staphylococcus aureus endophthalmitis: intravitreal injection of vancomycin and amikacin (VA/AN) in comparison with IV imipenem (IPM) and a combination of IV and IO (IV+IO) therapy.

METHODS

The right eyes of 27 rabbits were injected with 25000 S. aureus. After 24 h, animals were either treated with IO VA/AN ( n=5; 1.0 mg/0.4 mg in 0.1 ml saline), or IV IPM ( n=9; 37 mg/kg body weight 3x daily), or IV+IO therapy ( n=7), or served as untreated controls ( n=6). Clinical appearance was evaluated daily and vitreous aspirates were obtained for bacterial culture 24 h and 6 days after therapy, when the eyes were enucleated for histopathologic examination.

RESULTS

Eyes in the IO or IO+IV treatment group had a significantly better appearance clinically and histologically than did eyes in the IV or untreated control group. Eyes in the IO+IV group had a similar appearance to the IO-treated eyes. All aspirates from the IO and IO+IV groups were culture-negative 24 hours after therapy, whereas only five of nine in the IV-treated group were culture-negative. Aspirates from all treatment groups were culture-negative by day 6 after the initiation of therapy. Untreated control eyes were culture-positive at all times.

CONCLUSION

IO therapy with VA/AN proved more effective in treating experimental S. aureus endophthalmitis than did IV therapy with IPM alone. IV+IO treatment was not superior to IO treatment alone.