Addition of three new serotypes of Shigella boydii to the Shigella schema.

No new serotypes have been added to the Shigella schema since 1958, although several provisional serotypes have been described. We conducted biochemical and serological studies on three provisional Shigella boydii serotypes. Four strains of serotype 2710-54 from four widely separated countries, 7 strains of serotype 3615-53 from three different countries, and 31 strains of serotype 1344-78 (E10163) from six different countries were included. Reactions of all three serotypes were consistent with those of S. boydii. On the basis of these results and other published research, we propose that these three provisional serotypes be admitted to the Shigella schema as S. boydii 16, 17, and 18.