COMPLEMENT-SYSTEM AND HOST-DEFENSE AGAINST STAPHYLOCOCCAL ENDOPHTHALMITIS

Purpose. The authors studied the role of the complement system in host defense against Staphylococcus epidermidis and S. aureus endophthalmi tis. Methods. Guinea pigs in the S. epidermidis model received an intr avitreal injection of 7000 viable organisms, and guinea pigs in the S. aureus model received 50 viable organisms. The experimental animals i n each model were decomplemented with intraperitoneal (IP) injections of cobra venom factor, whereas the control animals received IP injecti ons of normal saline. Mean log bacterial counts in the vitreous and me an serum complement titers were compared in the experimental and contr ol animals in each model on days 1, 2, 3, and 7. Results. In the S. ep idermidis model, mean log bacterial counts in the vitreous were signif icantly higher in the experimental group than the control group on day s 1 and 2 (P < 0.01) and on day 3 (P < 0.05). Mean serum complement ti ters were significantly lower in the experimental group at all days (P < 0.01). In the S. aureus model, mean log bacterial counts in the vit reous were significantly higher in the experimental group than the con trol group an day 2 (P < 0.05) and day 3 (P < 0.01). Mean serum comple ment titers were significantly lower in the experimental group an days 1, 2, and 3 (P < 0.01), but not on day 7. Conclusion. These results s uggest that decomplemented guinea pigs show impaired host defense to S . epidermidis and S. aureus endophthalmitis and that this defense is r estored as complement levels approach normal.