FIG. 9.

F. tularensis ΔpyrF mutants retain the ability to replicate in normal fibroblasts. NHDF cells were infected with the designated LVS (A) or Schu S4 (B) strains (MOI, 500) using a gentamicin protection assay. NHDF cells were lysed at the indicated times, and the lysates were diluted and plated to enumerate CFU. Data shown are means ± SEM of results from triplicate wells within one experiment and are representative of at least three independent experiments. The abbreviations are the same as those in Fig. 4.