Binding of complement C3 to Klebsiella pneumoniae treated with sub-MIC cefodizime and chemiluminescence response of human polymorphonuclear leukocytes.

The binding of complement C3 to the cell surface of Klebsiella pneumoniae exposed to human serum complement after treatment with or without sub-MIC of antibiotics was examined by double diffusion immunoprecipitation against anti-human complement C3, and the production of oxygen-derived radicals by human polymorphonuclear leukocytes stimulated by complement-opsonized K. pneumoniae after treatment with or without sub-MIC of antibiotics was measured using the chemiluminescence (CL) assay. Complement C3 bound to the cell surface of K. pneumoniae treated with cefodizime was detected after exposure to human serum complement. The CL response induced by complement-opsonized bacteria after treatment with cefodizime was much higher than the response induced by nontreated bacteria or complement-opsonized bacteria after treatment with other antibiotics. These findings indicate that treatment with sub-MIC cefodizime make K. pneumoniae more susceptible to opsonization by complement and promotes the specific phagocytosis mediated by complement receptors.