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January 1996

Comparative Intravitreal Antibiotic Therapy for Experimental Enterococcus faecalis Endophthalmitis

Author Affiliations

From The Ocular Microbiology Laboratory, The Wilmer Ophthalmological Insitute, The Johns Hopkins University School of Medicine, Baltimore, Md.

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.