a, dot immunoblot of purified O157 lipopolysaccharide (LPS) spotted in duplicate and screened with pooled unadsorbed hyperimmune bovine sera. b, 1, dot immunoblot of O157 lipopolysaccharide spotted in duplicate (test); 2, colony immunoblot of four recombinant clones expressing PilA of Vibrio cholerae, an irrelevant protein (control); and 3, colony immunoblot of four recombinant clones expressing EspB of E. coli O157 (test) screened with pooled hyperimmune bovine sera adsorbed against purified E. coli O157 lipopolysaccharide.