Type-Specific and Cross-Reactive Antibodies in Gram-Negative Bacteremia

Antibody titers to O-specific and two shared cross-reactive antigens (common entero-bacterial antigen [CA] and a determinant [Re] of rough bacilli) were related to the frequency of shock or a fatal outcome in 175 patients with gram-negative bacteremia. High titers of O antibody did not prevent development of bacteremia and were associated with only a very slight decrease in the frequency of shock and death. The height of antibody titers to CA also did not correlate with the frequency of shock or a fatal outcome. In contrast, both shock and death were 1/3 as frequent among patients with high titers (1:80 or above) of Re antibody. The apparent protective effect of Re antibody was independent of any contribution of O antibody. These observations, coupled with prior animal studies, suggest that enhancement of resistance to enterobacteria might be accomplished by immunization with shared cross-reactive antigens.