Figure 3: Replication by F. novicida and mutant strains in A549 lung epithelial cells. Replication of U112 in A549 lung epithelial cells was compared to mutant strains ΔiglC, Δtul4, ΔmglA, Δ58kDa and ΔripA. U112 showed a significantly higher level of replication after 2hrs than ΔiglC, Δtul4, ΔmglA and ΔripA P< 0.0005, P< 0.005, P< 0.0005 and P< 0.005 respectively. After 6 hrs U112 replication level remains significantly higher than all of the mutant strains tested. P< 0.0005, P< 0.05, P< 0.0005, P<0.005 and P< 0.005. After 24 hrs the U112 replication level remained higher than attenuated mutants ΔiglC, ΔmglA, Δ58kDa and ΔripA P<0.0005 in all cases. On the other hand, U112 showed a lower level of replication than its non-attenuated mutant Δtul4 but the difference was not statistically significant. Comparing the 2 hrs time point with 6 and 24 hrs, we observed that U112, Δtul4 and ΔripA significantly increase their replication levels at 6 and 24 hrs P< 0.05. The Δ58kDa strain showed a significant increase in replication only after 24 hrs P<0.05. On the other hand, attenuated mutant strains ΔiglC and ΔmglA do not show any significant replication differences throughout the time points. (The statistical significance of increased replication between time points is not shown in the graph). The values are given in a log scale. * = P< 0.05, ** = P< 0.005 and *** = P< 0.0005