The Effect of Intravitreous Injection of Vancomycin on Postoperative Enterococcus Faecalis Endophthalmitis Model

Abstract

Purpose: : Post-cataract Enterococcus faecalis endophthalmitis is seen relatively often in Japan and carries a poor prognosis for vision. In this study, we examined the effect of intravitreous injection of vancomycin (VCM) on E. faecalis endophthalmitis using an aphakic rabbit endophthalmitis model we established.

Methods: : Japanese albino rabbits underwent lensectomy of the left eye by phacoemulsification and aspiration, and 1×10⁴colony-forming units (CFU) of E. faecalis OG1S (secreted protease-positive) were inoculated into each lens bag. One group of eyes received intravitreous injection of saline 6 hours later after inoculation (VCM(-)), and four other groups received intravitreous injection of VCM (1mg/0.1ml) 6, 12, 18, and 24 hours after inoculation. The severity of endophthalmitis was scored on a scale of 0-4, and electroretinography (ERG) was monitored over the course of the infection. The eyeballs were enucleated 48 hours after inoculation, the pathology of each group of eyes was comparatively monitored, and the bacteria in the aqueous humor and vitreous body were quantified.

Results: : Forty-eight hours after inoculation, the results for the VCM(-) group and the 6, 12, 18, and 24 hour VCM(+) groups, respectively, were as follows. The average endophthalmitis scores were 3.60, 2.25, 3.36, 3.33, and 3.45, and the ERG results (b-wave; test/control eye ratio) were 39.7, 138.0, 75.3, 92.8, and 51.8%. The viable bacteria counts (log10 CFU/tissue) were 5.74, 1.25, 1.09, 2.80, and 2.86 in the aqueous humor and 6.96, 2.91, 3.55, 5.32, and 5.52 in the vitreous body. From a pathological standpoint, groups that received intravitreous VCM earlier tended to show greater inhibition of inflammatory cell infiltration and tissue damage.The average endophthalmitis scores and reduction of ERG b-wave amplitudes in the 6 hour VCM(+) group improved significantly compared to those of the VCM(-) group (p<0.01). In the aqueous humor, there was significantly less bacterial growth in each of the VCM(+) groups compared to the VCM(-) group. In the vitreous body, bacterial growth in the 6 and 12 hour VCM(+)groups was significantly reduced (p<0.05).

Conclusions: : Early intravitreous injection of VCM may be able to suppress the progression of E. faecalis endophthalmitis.

Keywords: antibiotics/antifungals/antiparasitics • pathobiology • electroretinography: non-clinical