Purpose To evaluate the efficacy of vitrectomy with vancomycin for the treatment of experimental Bacillus cereus endophthalmitis. Methods Endophthalmitis was initiated in rabbits via intravitreal injection of 100 CFU B. cereus. Treatment groups included included 25-gauge transconjunctival sutureless vitrectomy with intravitreal vancomycin (1 mg) or vancomycin alone. Groups were treated at 4 h, 5 h, or 6 h postinfection. At 48 h (for 4 h and 5 h groups) or 36 h (for the 6 h group) postinfection, eyes were analyzed by electroretinography, histology, and inflammatory cell counts. Results Treatment with vitrectomy/vancomycin at 4 h resulted in significantly greater retinal function compared to that of vancomycin alone. Intraocular inflammation following treatment at 4 h was minimal for both treatment groups. Treatment with vitrectomy/vancomycin or vancomycin alone at 5 h or 6 h postinfection resulted in similar levels of retinal function loss (i.e. >90%) and significant intraocular inflammation. Conclusions These results demonstrate that vitrectomy may be of therapeutic benefit in the treatment of B. cereus endophthalmitis, but only during the early stages of infection.

Purpose/Aim Klebsiella pneumoniae causes a blinding infection called endogenous endophthalmitis. The role of innate immune recognition of K. pneumoniae in the eye during infection is not known. We hypothesized that intraocular recognition of K. pneumoniae was mediated by TLR4 and may be dependent on MagA-regulated hypermucoviscosity. Materials and Methods Experimental endophthalmitis was induced in C57BL/6J or TLR4−/− mice by intravitreal injection of 100 CFU of wild type or ΔmagA K. pneumoniae. Infection and inflammation were quantified by determining viable K. pneumoniae per eye, retinal responses via electroretinography, myeloperoxidase activity of infiltrating neutrophils, and the proinflammatory cytokine and chemokine response. Results C57BL/6J and TLR4−/− mice could not control intraocular wild type K. pneumoniae growth. TLR4−/− mice were less able than C57BL/6J to control the intraocular growth of ΔmagA K. pneumoniae. Retinal function testing suggested that infection with ΔmagA K. pneumoniae resulted in less retinal function loss. There was a TLR4-dependent delay in initial neutrophil recruitment, regardless of the infecting organism. The proinflammatory cytokine/chemokine data supported these results. These findings were not due to an inability of TLR4−/− neutrophils to recognize or kill K. pneumoniae. Conclusions These studies suggest that TLR4 is important in the early intraocular recognition and host response to K. pneumoniae. However, the role of MagA in TLR4-mediated intraocular recognition and subsequent inflammation is less clear.