An earlier study examined B. melitenesis ∆vjbR and ∆babR infections in a lethal challenge of IRF-1−/− C57BL/6 mice and found that, while ∆vjbR resulted in no mortality, ∆babR resulted in a mortality between that of ∆vjbR and 16M wild type (32). This evidence concerns the gene IRF1 and infection.