Phenotypic variations among enterotoxigenic O-groups of Escherichia coli from various human populations.

ETEC isolates from various sources (children from Ethiopia and some Asian countries, and Swedish tourists suffering from traveller's disease) were analysed with the aid of "biochemical fingerprinting", which is a highly discriminative, computerized method designed to subdivide E. coli isolates into different phenotypes. Isolates belonging to the most common ETEC O-groups and others which had not been typeable with available O-antisera were selected. It was found that certain phenotypes of O-groups 6 and 114 could be found in materials from several continents. Phenotypes of other O-groups were usually more restricted to certain geographic areas. Among children in Addis Abeba, 19 out of 25 isolates carrying O-antigen 78 belonged to the same phenotype. Some possible explanations for the fact that certain phenotypes of enterotoxigenic E. coli could be found over the whole world are that they might represent relatively recent developed clones, or they may represent unusually stable clones. Of the isolates that had been nontypeable with available antisera, some had lost their LT-productivity after one year of storage. These isolates proved to belong to a wide variety of phenotypes, whereas nontypeable isolates which were stable LT-producers could be clustered into distinct groups. It is suggested that the non-stable LT-producers are members of the normal E. coli flora of these children, which have occasionally picked up the enterotoxin-producing plasmids, whereas most stable LT-producers represent true ETEC clones.