A new provisional serovar of Shigella dysenteriae.

Bacterial isolates obtained in Israel from stool cultures of 17 sporadic cases of acute diarrhea during the years 1972 to 1980 and from 14 patients involved in an institutional outbreak in 1984 are described. These cultures gave the biochemical reactions and pathogenicity tests characteristics of the genus Shigella but failed to agglutinate, living or boiled, in any of the recognized or provisional Shigella antisera. All 31 cultures were biochemically and serologically identical, and owing to their inability to ferment mannitol, it is proposed that they be regarded as belonging to a new provisional serovar of Shigella dysenteriae. The strain I9809-73 is designated as the test strain for this new serovar.