Comparative analysis of antibodies to the lipopolysaccharides and to cross-reactive enterobacterial outer membrane proteins in patients with enteritis caused by Salmonellae or Yersinia enterocolitica

Abstract

Sera from patients with recent or ongoing Salmonella ( n = 25) or Yersinia enterocolitica O3 enteritis ( n = 32), were tested by ELISA for antibodies cross-reacting with outer membrane (OM) proteins from an Escherichia coli O55 strain. In addition, the sera were tested by ELISA for serotype-specific antibodies against lipopolysaccharides (LPS ELISA) from Salmonellae or Y. enterocolitica O3. The results were matched against those obtained by testing healthy controls ( n = 30). The LPS ELISAs proved their efficacy in diagnosing enteritis caused by the Salmonellae or Yersinia with positive tests in 96% and 100% respectively. Significantly elevated means of the levels of cross-reacting anti-OM protein antibodies were shown for all of the immunoglobulin classes IgA, IgG, and IgM. These antibody rises were less marked than those of the anti-LPS antibody rises. Levels of the two groups of antibodies showed no correlation in individual patients. The cross-reacting antibodies were directed against OM proteins which varied from one individual to another and which included the porin protein, OmpA, the peptidoglycan-associated lipoprotein, and Braun's lipoprotein. The findings emphasize that cross-reacting antibodies may reduce specificity of serodiagnostic test for Salmonella or Yersinia-induced enteritis unless highly purified antigens are used.