Az inhibition of intracellular F. novicida mutants. A) J774A.1 and B) A549 cells were infected with various mutants at an MOI 500. At 22 hours, the number of CFUs/ml recovered from F. novicida multidrug efflux mutants ftlC, tolC, acrA, and acrB and LPS O-antigen mutant wbtA decreased as Az concentrations increased and was near 0 CFU/ml at 35 μg/ml Az (p-value < 0.005 for all Az treatments compared to 0 μg/ml Az for each mutant). The recovery of mutant strains after Az treatments were significantly different from the wild-type F. novicida with a p-value < 0.05 (1.76 × 105 ± 6.36 × 103 CFU/ml in J774A.1 at 0 μg/ml Az which decreased to 0 CFU/ml at 5 μg/ml Az and 1.80 × 105 ± 1.41 × 104 CFU/ml in A549 cells at 0 μg/ml Az which decreased to 0 CFU/ml at 25 μg/ml Az). J774A.1 cells had higher bacterial counts than A549 cells.