has role virmugen Brucella abortus gene virmugen role exsA from B. abortus NCBI_Gene_ID: 3787220; PMID: 12183550 gene Brucella DeltaexsA mutant showed decreased survival in mice compared to the survival of parental strain S2308. This demonstrated that ExsA is critical for full bacterial virulence. The B. abortus exsA deletion mutant was used as a live vaccine candidate. Challenge experiments revealed that the exsA mutant strain induced superior protective immunity in BALB/c mice compared to the protective immunity induced by strain S19 or RB51 Rebecca Racz Oliver He