Characterization of an Experimental Murine Model of Bacillus Endophthalmitis

Abstract

Abstract: : Purpose: To establish an experimental murine model of Bacillus endophthalmitis for the evaluation of neurophysiological, immunological, and architectural changes associated with the evolution of infection. Methods: C57BL6 mice were injected intravitreally with 2 log₁₀ cfu of vegetative Bacillus cereus. Contralateral eyes were injected with PBS or were left undisturbed. Infection courses were analyzed every 2 hours for 12 hours by biomicroscopy, electroretinography, immunohistochemistry, and quantitation of intraocular inflammatory cell influx and bacterial growth. Results: Bacillus grew rapidly to a plateau of 9 log₁₀ cfu per eye within 10 hours. Viable organisms were observed throughout the posterior segment within 8 hours, and in all parts of the eye within 12 hours. Retinal function declined precipitously and was absent by 10 hours postinfection. Cellular infiltration near the optic nerve was observed as early as 4 hours postinfection. Influx of inflammatory cells from the iris and ciliary body into the aqueous was observed at 8 hours postinfection. Retinal architecture remained intact throughout 6 hours. At 8 hours, retinal detachments and disruptions in retinal architecture began to occur. Retinal layers were indistinguishable by 12 hours postinfection. Conclusions: The murine model of Bacillus endophthalmitis was highly reproducible in terms of retinal function declines, evolving inflammation, and intraocular bacterial growth and migration, and is similar to well-established experimental rabbit models of Bacillus endophthalmitis. The murine model will greatly facilitate detailed analyses of the molecular and cellular events involved in the primary mechanisms of pathogenesis, which is essential for the development of innovative target-based therapeutics for the preservation of vision during Bacillus endophthalmitis.

Keywords: bacterial disease • endophthalmitis • animal model