The defect in the metabolism of erythritol of the Brucella abortus B19 vaccine strain is unrelated with its attenuated virulence in mice.

The role of the defect in erythritol catabolism in the attenuated virulence of Brucella abortus B19 vaccine strain in mice was investigated by means of five different strains: (i) the erythritol sensitive B19 vaccine strain; (ii) a natural erythritol tolerant (NET) mutant obtained spontaneously from B19; (iii) an erythritol resistant derivative from B19 (FJS19) obtained by gene replacement of the deleted ery region; (iv) the erythritol resistant B. abortus 2308 reference virulent strain; and (v) an erythritol sensitive mutant (227 strain) obtained from strain 2308 by transposon insertion in the chromosomal ery region. Besides virulence for mice, erythritol oxidation as well as other phenotypic markers were tested in all the strains. The 2308 and FJS19 strains grew in the presence of erythritol and oxidized the sugar, whereas the B19 and 227 strains did not. The NET strain grew in presence of erythritol but was unable to oxidize it. The B19 vaccine strain and its two erythritol resistant derivatives, NET and FJS19, showed similar residual virulence and splenic time courses in mice. Moreover, the virulent strain 2308 and its erythritol sensitive derivative (227 strain) exhibited similar levels of splenic infection. Altogether, these results demonstrate that the genetic region implicated in erythritol catabolism is not related to the low virulence exhibited by B19 in mice.