Serological variety of flagellar antigen H1 in natural Escherichia coli population.

Variation of the Escherichia coli flagellar antigen H1 was studied among 120 human isolates belonging to more than 25 O:K serovars. Factor-specific antisera were prepared and shown to be useful in the identification of serological subtypes of H1. The three subtypes found were defined as H1abc, H1acd and H1abe. The H1abc corresponded to the standard flagellar antigen H1 present in 84% of all strains. It was found in all O groups except O15, O17 and O83. Eight O15 and two O17 strains studied were of subtype H1abe, while the one O83 strain studied was H1acd. Both subtypes H1abc and H1acd were found among strains within O6:K5, O6:K13 or O-non-typeable:K5 serovars.