Construction of a novel serotype, 1 d, of S. flexneri with serotype-converting bacteriophages SfX and SfI. (A) Illustration of construction road map of S. flexneri 036_1d strain from a serotype Y strain 036, by sequential infection of phages SfX and SfI. (B) Serological identification of S. flexneri 036_1d as serotype 1 d with agglutination test using monovalent diagnostic sera. The constructed strain S. flexneri 036_1d agglutinated with both of typing sera I and grouping sera7;8. (C) Serological identification of S. flexneri 036_1d by Western-blot assay. The LPS extracted from the tested strains was separated by SDS-PAGE and hybridized with monovalent grouping sera 7;8 (a) and 3;4 (b), and typing sera I (c), respectively. LPS of serotype X strain 014 and serotype 1a strain 019 were used as positive controls for group specific antigen 7;8 and type specific antigen I. After strain name in brackets is the serotype of the strain.