Serological assay for diagnosis of verotoxin-producing Escherichia coli (VTEC) infection in the patients with diarrhea

Abstract

A total of 239 serum samples from 136 persons were used for bacterial agglutination assay (BA) against predominant three O-antigens of VTEC. All VTEC isolates from stools of 30 patients were only O157:H7 serotype (these patients are called group I). The levels of positive BA antibody titers (over 1:160) to O157-antigen were recognized in each patients as follows. The VTEC isolated patients with HUS or without HUS in group I were all of 13 (100%) and 14 (82.4%) in 17 patients, respectively. And 21 (65.6%) patients of group II (HUS patients with stool negative cultures, or stool cultures were not performed in 32 patients), and 6 (15.0%) patients of group III (family members of group I and II; 40 persons), were also recognized. In group IV (patients with diarrhea due to other pathogen than VTEC; 11 patients), and V (clinically healthy persons; 23 persons), none were recognized as positive BA antibody titers. All patients in the group II except one who had a positive BA antibody titer to O111, were not recognized to O111 and O26. A few VTEC-positive patients without gastrointestinal syndrome did not have significant agglutinating titers to O157-antigen on the days after VTEC isolation. However, almost all patients with diarrhea due to VTEC and HUS, and with VTEC but no HUS, had a level of positive BA antibody titer on the 5 day after onset of diarrhea. These results suggest that this serological assay is a very simple and useful tool for diagnosis of VTEC infection when VTEC are not detected by culture method due to antimicrobial treatment, or due to the lapse of many days after onset of diarrhea.