Isolation and pathogenicity of provisional serovar 1621-54 of "Shigella" from imported cynomolgus monkeys.

The provisional serovar 1621-54 of "Shigella" was isolated from 36 (13.2%) of 273 cynomolgus monkeys newly imported into Tsukuba Primate Center for Medical Science (TPC) from Indonesia during the period from 1980 through 1981. The biochemical properties of the isolates were in good agreement with those of previously described provisional "Shigella" serovar 1621-54. Clinically, 13 (36.1%) of 36 monkeys being positive for the organisms excreted diarrheal stools on arrival at TPC. In addition, the organisms were isolated also from three other monkeys contracting dysentery during the quarantine period at TPC. One of them died 2 days after the onset of dysentery. Histopathological findings of this case were essentially the same as those of Shigella-infected monkeys. Pathogenicity of the isolates was examined in three experimental infection models; (1) the infection model using cultured HeLa-S3 cells, (2) the keratoconjunctival infection model of the guinea pig, and (3) the intestinal infection model of the cynomolgus monkey. All the strains tested showed positive results in these experimental models, causing intracellular penetration and multiplication in HeLa-S3 cell cultures, keratoconjunctivitis in guinea pigs, and dysentery in cynomolgus monkeys. These results indicate that provisional "Shigella" serovar 1621-54 is a causative agent of dysentery in man as well as in monkeys.