The distribution of, and antibody response to, the core lipopolysaccharide region of Escherichia coli isolated from the faeces of healthy humans and cattle.

There are five different core types of Escherichia coli lipopolysaccharide (LPS), and enterohaemorrhagic E. coli tend to have the R3 core type. It has been hypothesized that increased carriage of bacteria with a specific core type will induce higher levels of antibodies and protect against disease caused by bacteria carrying that specific LPS core. Approximately 320 isolates of E. coli, half from healthy human faeces and half from healthy bovine faeces have been core typed both by core-specific monoclonal antibodies, and by PCR for genes encoding the enzymes responsible for the biosynthesis of the specific core structures. Results showed that E. coli possessing R1 core LPS were most frequently detected in both human and cattle populations (63 and 49%, respectively). Compared to the human isolates a significantly higher level of bacteria with R3 core LPS was detected among the bovine commensal E. coli (11% compared to 4%; P < 0.05). Antibody levels to each of the specific core types were measured in serum samples from healthy humans (n = 91) and healthy cattle (n = 39). In each population the highest level of antibody detected was reactive to the R4 core. In cattle the level of anti-R3 core antibody was significantly higher than the level of anti-R1, -R2 and -K12 antibodies (P < 0.01). In summary there was a greater proportion of E. coli with R3 core type in cattle, together with a corresponding higher anti-R3 antibody level. This suggests that cattle may have greater immunity to E. coli strains with an LPS of R3 core type.