The contribution of the pADI-encoded cytolysin to Enterococcus faecalis virulence in an experimental endophthalmitis model was studied by using isogenic strains differing only in the location of transposon Tn917. The course of experimental endophthalmitis in New Zealand White rabbits was evaluated by postoperative reduction in retinal neuroresponsiveness, thin-section histopathology, and transmission electron microscopy. Infections caused by cytolytic E. faecalis resulted in 99% loss of retinal function at postoperative day 3, while isogenic, noncytolytic strains produced reductions of only 74.2%. Light microscopy revealed near-total destruction of retinal architecture at 24 h postinfection with cytolytic E. faecalis, while noncytolytic strains produced few or no destructive changes. Transmission electron microscopy revealed tissue destruction in retinal layers as eariy as 6 h postinfection with cytolytic E. faecalis. In vivo and in vitro growth rates of cytolytic and noncytolytic E. faecalis showed similar kinetics. These data demonstrate the contribution of the pADI-encoded cytolysin to both the course and the severity of experimental E. faecalis endophthalmitis.

The fluoroquinolones ofloxacin, ciprofloxacin, and norfloxacin had higher overall in vitro efficacy than the other antibiotics tested. Of the fluoroquinolones, ofloxacin had the highest in vitro efficacy against gram-positive organisms. All three fluoroquinolones were equivalent in efficacy against gram-negative organisms.

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