Some characteristics of a urease-negative, temperature- sensitive strain of Bordetella bronchiseptica as a live, attenuated vaccine.

Strain ts-S34 of Bordetella bronchiseptica was treated jointly with two mutagens, nitrosoguanidine and UV irradiation, and a urease-negative (u-), temperature-sensitive (ts) mutant strain indistinguishable from Alcaligenes faecalis in its biochemical characteristics was isolated. However, the mutant isolated was a phase III organism. By repeating selection of smaller, hemolytic colonies observed among phase III colonies after prolonged incubation, a phase I organism, strain ts-S34.u-, was isolated. The u- and ts properties of the mutant strain were hereditarily stable, and heat-labile toxin production was very low. Growth in KCN broth and on Simmons citrate agar was reduced. Agglutinability of the strain against anti-S1 and anti-ts-S34.u- hyperimmune sera was as high (X20,480) as that of wild-type strain S1. The live ts-S34.u- strain vaccination protected guinea pigs from challenge exposure with 15,000 X the 50% lethal dose of virulent strain S1 of B. bronchiseptica. In these studies, it appeared that the ts-S34.u- strain has favorable properties, including a useful hereditary marker and low heat-labile toxin production, for use as a live attenuated vaccine.