Generation ofEscherichia coliO9a Serotype, a Subtype ofE. coliO9, by Transfer of thewb* Gene Cluster ofKlebsiellaO3 intoE. colivia Recombination

Genetic characterization of the wb* gene in a series of Escherichia coli and Klebsiella strains possessing the mannose homopolymer as the O-specific polysaccharide was carried out. The partial nucleotide sequences and PCR-restriction fragment length polymorphism analysis suggested that E. coli serotype O9a, a subtype of E. coli O9, might have been generated by the insertion of the Klebsiella O3 wb* gene into a certain E. coli strain.