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January 1996

Comparative Intravitreal Antibiotic Therapy for Experimental Enterococcus faecalis Endophthalmitis

Arch Ophthalmol. 1996;114(1):61-65. doi:10.1001/archopht.1996.01100130057009

Objective:  To evaluate the most effective intravitreal antibiotic treatment of vancomycin-sensitive and -resistant Enterococcus faecalis endophthalmitis.

Design:  Animal experiment.

Setting:  Seventy-eight New Zealand white rabbits received an intravitreal injection of 105 vancomycin-sensitive or -resistant E faecalis organisms in one eye. Infections were allowed to proceed 3 hours before dividing animals randomly into the following treatment groups (n=6, each): the vancomycin-sensitive E faecalis model—(1) vancomycin (1 mg/0.1 mL), (2) combined vancomycin (1 mg/0.1 mL) and amikacin (0.4 mg/0.1 mL), (3) combined vancomycin (1 mg/0.1 mL) and gentamicin (0.1 mg/0.1 mL), (4) combined vancomycin (1 mg/0.1 mL) and ceftazidime (2 mg/0.1 mL), (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, vitreous humor was collected for quantitative bacteriological studies.

Results:  Intravitreal therapy with combined vancomycin and amikacin provided the most effective reduction of vancomycin-sensitive E faecalis organisms compared with combined vancomycin and gentamicin therapy (P=.10, Wilcoxon's rank sum test) or any other treatment group (P<.01, Wilcoxon's rank sum test). For vancomycin-resistant E faecalis endophthalmitis model, the combined ampicillin and gentamicin therapy was the most effective, followed by the combined vancomycin and amikacin therapy (P<.01, Wilcoxon's rank sum test).

Conclusions:  Treatment with intravitreal vancomycin plus amikacin and with intravitreal ampicillin plus gentamicin provide an effective bactericidal therapy for severe experimental vancomycin-sensitive and -resistant E faecalis endophthalmitis, respectively.