The reference strains belonging to various O- and H-antigen groups representing the flagella antigens H1 to H56 were included in this study, (10) and they were obtained from the E.
(11) The production and absorption of antisera and tube H-antigen agglutination were carried out as described previously by Ewing (1986).
Antibody cross-absorption assays were carried out, and the H-antigen agglutination tests were performed in tubes.
To correlate the H-antigen pattern with fliC polymorphisms, PCR-amplified fliC fragments were subjected to RFLP analysis.
coli strains were motile but, non-typeable by serotyping, the determination of fliC polymorphism might be a quick altenative for H-antigen typing.
(7,8) However, non-typeable strains have fliC RFLP patterns that did not correspond to the pattern identified for the H1 to H56 antigens and might therefore represent novel H-antigen types.
Species-wide variation in the Escherichia coli flagellin (H-antigen) gene.
coli is applied as routine laboratory standard: (I) the expression of H-antigens can be dependent on various environmental signals and identification of the complete set of serotypes is a time-consuming process and requires the use of 53 specific antisera; and (II) there is a great deal of cross-reactions among E.
To determine the O- and H-antigens, we used antisera against reference E.
H antigens associated with O91 were H8 (n = 1), H10 (n = 2), H14 (n = 52), H21 (n = 20), Hnt (H-antigen nontypeable) (n = 10), and H- (H-antigen nonmotile) (n = 15).
MLST analysis divided the O91 isolates into 10 different STs, whereas classical serotyping identified only 4 complete serotypes (O- and H-antigen).
(n = 4) (n = 8) (n = 79) (n = 9) strains ST33 (O91:H14/ [H.sup.-]/Hnt) 0 5 51 7 63 ST442 (O91:H21) 4 3 12 1 20 ([dagger]) ST641 (O91:H10) 0 0 2 0 2 ST690 (O91:H14) 0 0 8 1 9 ST1020 (O91:H8) 0 0 1 0 1 ST1048 (O91:H14) 0 0 1 0 1 ST1051 (O91:H14) 0 0 1 0 1 ST1052 (O91:H14) 0 0 1 0 1 ST1053 (O91:H14) 0 0 1 0 1 ST1054 (O91:Hnt) 0 0 1 0 1 * ST, sequence type; STEC, Shiga toxin-producing Escherichia coli; H, H-antigen nonmotile strains; Hnt, H-antigen nontypeable strains; HUS, hemolytic uremic syndrome; BD, bloody diarrhea; D, diarrhea without visible blood; A, asymptomatic infection (1 patient infected with ST442 [STEC O91:H21] had abdominal cramps without diarrhea).