COMPARATIVE INTRAVITREAL ANTIBIOTIC-THERAPY FOR EXPERIMENTAL ENTEROCOCCUS-FAECALIS ENDOPHTHALMITIS

Objective: To evaluate the most effective intravitreal antibiotic trea tment of vancomycin-sensitive and -resistant Enterococcus faecalis end ophthalmitis. Design: Animal experiment. Setting: Seventy-eight New Ze aland white rabbits received an intravitreal injection of 10(5) vancom ycin-sensitive or -resistant E faecalis organisms in one eye. Infectio ns were allowed to proceed 3 hours before dividing animals randomly in to the following treatment groups (n=6, each): the vancomycin-sensitiv e E faecalis model-(1) vancomycin (1 mg/0.1 mL), (2) combined vancomyc in (1 mg/0.1 mL) and amikacin (0.4 mg/ 0.1 mL), (3) combined vancomyci n (1 mg/0.1 mL) and gentamicin (0.1 mg/0.1 mL), (4) combined vancomyci n (1 mg/0.1 mL) and ceftazidime (2 mg/0.1 mt), (5) combined ampicillin (5 mg/0.1 mL) and gentamicin (0.1 mg/ 0.1 mL), and (6) pristinamycin (1 mg/0.1 mL); and the vancomycin-resistant E faecalis model-(1) same as above, excluding group 4. Control groups received sterile balanced salt solution. Twenty-four hours following intravitreal treatment, vit reous humor was collected for quantitative bacteriological studies.Res ults: Intravitreal therapy with combined vancomycin and amikacin provi ded the most effective reduction of vancomycin-sensitive E faecalis or ganisms compared with combined vancomycin and gentamicin therapy (P=.1 0, Wilcoxon's rank sum test) or any other treatment group (P<.01, Wilc oxon's rank sum test). For vancomycin-resistant E faecalis endophthalm itis model, the combined ampicillin and gentamicin therapy was the mos t effective, followed by the combined vancomycin and amikacin therapy (P<.01, Wilcoxon's rank sum test). Conclusions: Treatment with intravi treal vancomycin plus amikacin and with intravitreal ampicillin plus g entamicin provide an effective bactericidal therapy for severe experim ental vancomycin-sensitive and -resistant E faecalis endophthalmitis, respectively.