In vitro markers and biological activity in mice of seed lot strains and commercial Brucella melitensis Rev 1 and Brucella abortus B19 vaccines.

Four seed lots and fourteen batches of Brucella melitensis Rev 1 and B. abortus B19 living anti-Brucella commercial vaccines obtained from six Spanish laboratories were tested in vitro and in vivo in the reference mouse model for quality control. All the strains tested showed the characteristic morphology of their respective Rev 1 or B19 reference strains with the exception of three Rev 1 strains: seed lot SL2 and commercial vaccine R3, in which giant colonies were predominant, and commercial vaccine R5, in which 5% rough colonies were detected. Strains SL2 and R5 (but not the R3) had a deficient activity when tested in the mouse model. All strains but two (Rev 1 strain R1 and B19 strain B2) had standard resistance/ sensitivity patterns to streptomycin and penicillin G. Strains R1 and B2 had an increased resistance to penicillin when incubated in a 10% CO2 atmosphere and both strains showed an increased residual virulence in mice. As residual virulence and immunogenicity in mice were not always correlated one another nor with the in vitro tests, all tests should be performed to control properly the anti-Brucella live vaccines. A computerized statistical procedure to calculate the residual virulence of vaccines is proposed as an alternative to that used in the current method.