Fig. 1

Fn survives inside human neutrophils. Human neutrophils from healthy donors were exposed to Fnn, Fnp, and Fn with deletion of the Fap2 or RadD genes at MOI of 1, 20, or 100. After exposure, the neutrophils were washed to remove all Fn that was not phagocytosed. To confirm the viability of intracellular bacteria, we treated Fn-laden neutrophils with gentamicin for 1 hour, washed them out of the drug, and incubated them for a further 3.5 hours. At 5 hours post-infection, we centrifuged samples and plated out the supernatant and the lysed neutrophil pellet on blood agar media to compare the viability of escaped (extracellular) bacteria in the supernatant to intracellular bacteria in the neutrophil pellet. Intracellular bacteria viability was measured four days after plating and expressed as square root transformation of colony-forming units (CFU). S. mitis, readily killed by neutrophils, was used as a control (N > 14). Plots show individual data points, mean and standard error of the mean (SEM).