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Shigella is a nonmotile gram-negative bacillus, belonging to the Enterobacteriaceae family. The organisms orally taken in invade the epithelial cells of the large intestine to cause shigellosis with (mucous and bloody) diarrhoea, fever and abdominal pain as chief complaints. Shigella is classified into the following 4 species by serological properties of somatic antigens (O antigens) and biochemical properties according to the recommendation (1984) of the International Enterobacteriaceae Grouping Subcommittee based on Ewing’s proposal in 1949:    S. dysenteriae (subgroup A), S. flexneri (subgroup B), S. boydii (subgroup C) and S. sonnei (subgroup D). S. dysenteriae is classified into 12 serologic types by antigen type, S. flexneri into 6 serotypes and 13 subtypes by antigen type and group, S boydii into 18 serotypes by antigen type. There is one serotype as for S. sonnei, which is classified into 2 antigens, phase I (smooth: S type) and phase II (rough: R type) according to the S-R mutation of the O antigen.

These products are polyvalent sera or monovalent sera used for serotyping of Shigella by slide agglutination, each of which contains a specific agglutinin. Each polyvalent serum is prepared by hyperimmunizing healthy pigs with the inactivated organisms, heating the obtained serum at 56°C for 30 minutes, removing analogous agglutinins with suction and aseptically filtrating them. As for monovalent sera, healthy rabbits are hyperimmunized to obtain sera.