Bacillus causes one of the most explosive and devastating forms of post-traumatic or endogenous endophthalmitis that, despite aggressive antibiotic and surgical intervention, almost always results in blindness, if not loss of the eye itself. The regularity of treatment failures highlights the need for identification and characterization of the specific virulence factors involved in pathogenesis and significant improvements in existing treatment regimens. Studies conducted during the initial funding period addressed the contributions of bacterial factors to Bacillus endophthalmitis, namely bacterial cell walls, toxins, and intraocular motility. Results suggested that all factors contributed to virulence, to varying degrees. We identified the most important bacterial intraocular virulence factors to be quorum sensing regulation of toxin production and migration of Bacillus throughout the eye during infection. The most important host contributor to virulence appears to be the rapid influx of inflammatory cells into the posterior segment at the early stages of infection. These factors represent important potential targets for the development of novel therapeutics for Bacillus endophthalmitis. This proposal extends the identification of critical bacterial factors involved in virulence to identify additional therapeutic targets. To do this, we propose to analyze the virulence of strains deficient in metalloproteases, motility, or surface components, and Bacillus spores as infective agents in the eye. The proposal then shifts toward the development of improved antibiotic/anti-inflammatory therapeutic regimens for the treatment of Bacillus endophthalmitis. We propose to directly target the bacterium and the host inflammatory response during the critical, early stages of intraocular infection when initial retinal function changes are occurring. Agents designed to interfere with Bacillus growth or host inflammation will be evaluated during the course of this project, the results of which are expected to be of immediate clinical relevance in designing more rational therapeutic regimens aimed at limiting the sight-threatening consequences of intraocular infection and inflammation. These studies are a logical consequence of the original proposal, and as such will greatly advance our long-range goal of understanding the pathogenic mechanisms of disease and developing successful treatment strategies for the preservation of vision during Bacillus endophthalmitis. [unreadable] [unreadable] [unreadable]