Complement Component C9 Enhances the Capacity of Beta-Lactam Antibiotics to Kill Escherichia coli In Vitro and In Vivo

ABSTRACT Complement component C9 is re¬quired for rapid complement-mediated killing of Escherichia coli. In this report, the influence of supplemental C9 on the bactericidal and protec¬tive effects of beta-Iactam antibiotics in neo¬nates was assessed. By rocket immunoelectro¬phoresis, the intrinsic C9 concentrations of pooled serum from both human and rat neo¬nates was less than 20% of adult levels. Supple¬mental C9 purified from human plasma en¬hanced the capacity ofampicillin-treated serum from human neonates to impair the survival of E coli 07:K1:NM (P