NOS2 and infection: Like Mycobacterium tuberculosis[34], [35],[36], and in contrast to other intracellular bacteria such as Listeria monocytogenes[37] or Legionella pneumophila[38], B. melitensis does not irreversibly affect the health status of the majority of mice genetically deficient for key element of Th1 protective immune response (such as MyD88 [10],[39], IL-12p40 [11], IFN-γ [12] and iNOS [11]) during the first four weeks of infection.