Postoperative Enterococcus faecalis endophthalmitis: virulence factors leading to poor visual outcome

Purpose Postoperative endophthalmitis caused by Enterococcus faecalis often results in poor visual outcome due to retinal destruction. We evaluated the virulence factors of Enterococcus faecalis clinical isolates and analyzed their relationship with retinal destruction and poor visual outcomes in postoperative bacterial endophthalmitis (PBE) following cataract surgery.

Retrospective.

E. faecalis isolates from nine acute-onset PBE cases were examined using pulsed-field gel electrophoresis of genomic DNA, plasmid isolation and pheromone response experiments. Virulence determinant genes, including cytolysin (cylA), aggregation substance (asa1), enterococcal surface protein (esp), gelatinase (gelE) and adhesin of collagen from enterococci (ace), were examined by polymerase chain reaction. Expression of cytolysin and secreted protease were also tested. Retinal findings observed during vitrectomy surgery and final visual acuities were compared to obtained microbiological data. Poor visual outcome was defined as final visual acuity of less than 0.1 (decimal).

Although nine isolates were collected, two were identical. Out of the eight different isolates, three were positive for both expressions of cytolysin and secreted proteases. Plasmid DNAs were isolated from six of eight isolates, while pheromone response was observed in five isolates. The asa1, esp and ace genes were positive in six, five and eight of the isolates, respectively. Patients with retinal destruction exhibited significantly higher prevalence of secreted protease expression versus those without (P < 0.05), and retinal destruction was related to poor visual outcome (P < 0.05).

Our data suggest that enterococcal secreted proteases were correlated to retinal destruction, thereby fostering poor visual outcomes in eyes with enterococcal endophthalmitis.