Antibiotic resistance pattern and visual outcome in experimentally-inducedStaphylococcus epidermidis endophthalmitis in a rabbit model

Objective: To study whether the clinical outcome of Staphylococcus epidermi dis-induced endophthalmitis in rabbits is related to the antibiotic resista nce pattern of the infecting strain. Design: Experimental animal study. Participants: The right eyes of 36 New Zealand white albino rabbits were in oculated with strains of S. epidermidis that displayed various patterns of antibiotic resistance. Methods: There were 12 rabbits in each of three study groups: fully antibio tic susceptible (FS), partially antibiotic resistant (PR), and multiresista nt (MR). Five days after inoculation, the eyes were enucleated and prepared for histologic studies. Main Outcome Measures: Comparisons among the three groups were made based o n electroretinographic (ERG) findings, histologic evaluation by a masked ob server, and clinical examination. Results: Electroretinographic findings on all rabbits were made by an unmas ked observer. At 30 hours after inoculation, the ERG was diminished to 65% of normal for group FS, compared with a fiat ERG waveform for groups PR (P < 0.05) and MR (P < 0.05). The ERG waveform was flat for all three groups a t 72 hours after inoculation. Histologic evaluation by use of a histologic score revealed that the degree of inflammation and destruction of the retin a was less for group FS (n = 10) compared with groups PR (n = 8) and MR (n = 8). Clinical examination revealed that there was a trend of less ocular i nflammation for group FS compared with groups PR and MR. Conclusions: in a rabbit model of S. epidermidis-induced endophthalmitis, a ntibiotic-susceptible strains caused less inflammation and destruction of t he infected retina than did antibiotic-resistant strains. (C) 2001 by the A merican Academy of Ophthalmology.