IFNG and infection: While in vitro studies revealed no difference between growth of wild-type MAC104, MAV_4644 gene knockout and complemented strains in the liquid culture medium (Figure 3A); the MAV_4644:Tn mutant was attenuated with approximately 1.5 log to grow within IFN-γ stimulated RAW264.7 macrophages when compared to the wild-type MAC104 infection (Figure 3B).