Role of antibodies and antibiotics in aerobic gram-negative septicemia: possible synergism between antimicrobial treatment and immunotherapy.

Recovery from gram-negative septicemia depends on the successful joint action of antibiotics and host defense mechanisms. The possible enhancement of host defense with either immunotherapy or antibiotic treatment has been the subject of numerous investigations. Because of the great similarity of core epitopes within different species of Enterobacteriaceae, most studies have focused on the development of cross-reactive and/or cross-protective antibodies to these common epitopes. The majority of strains that cause severe gram-negative septicemia, however, possess a complete O antigen (and often a K antigen) that may camouflage the common antigenic determinants. Antibodies to these common antigens therefore may be unable to recognize their targets. Subinhibitory concentrations of certain antibiotics have been shown to alter surface structures of Enterobacteriaceae to such an extent that the structures no longer camouflage underlying epitopes, allowing binding of cross-reactive or cross-protective antibodies to these epitopes. Thus antibiotics and antibodies may synergistically fight infection.