Heterogeneity of immunotypes of heat-labile enterotoxins of enterotoxigenic Escherichia coli of human origin

Abstract

A new technique, checkerboard immunoblotting (CBIB), has been applied to detect and to differentiate heat-labile enterotoxins, (LTs), from enterotoxigenic strains of Escherichia coli of human origin using polyclonal and monoclonal antibodies. Optimal conditions of production and release of LTs were defined using CBIB. LT release was enhanced when E. coli cells were treated with 8 M urea. LT production was highest when E. coli strains were incubated with shaking (200 rpm) at 37 degrees C for 12 h in CAYE-2 medium. Two hundred and five strains of E. coli, isolated from patients with diarrhea in Japan, Thailand, the United States, Mexico, and Brazil, were examined for LT. Of 133 LT-positive strains, 4 (3%) produced an LT that reacted like H-LT-1 (originally isolated from E. coli strain H-74-114) while 126 strains (94.7%) produced LT that reacted like H-LT-2 (originally isolated from strain H-10407) or H-LT-3 (from strain H-240-3). Three strains of human origin (2.3%) produced an LT that reacted like P-LT (produced by E. coli strains of porcine origin). This study shows that CBIB, a simple, efficient, and practical assay, might be useful for epidemiologic surveys and for evaluation of serologic responses to LTs and antitoxic vaccines.