The Role of Complement in Limiting Bacteremia Caused by Streptococcal L-Phase Variants 1

Abstract

Bacterial L-phase variants may participate in the pathogenesis of some infectious diseases. Previous studies performed in vitro have demonstrated that L-phase variants of Streptococcus faecalis are able to activate both the classical and alternative pathways of complement and that this activation results in death of the organism. The present study was performed in order to determine whether the complement system serves a protective role, in vivo, against L-phase variants of S. faecalis. Mice were depleted of the third component of complement (C3) by treatment with purified cobra venom factor. The C3 depleted mice had a significantly greater magnitude of bacteremia at 1 and 3 hr after the intraperitoneal injection of L-phase variants of S. faecalis than did control animals. Both groups of animals yielded sterile blood cultures at 8 hr. These studies suggest that the complement system participates in the host's defense against L-phase variants of bacteria.