Fig. 3. Adhesion versus internalization of N. meningitidis. Approximately 10⁷ bacteria (ROU strain of N. meningitidis) in culture medium were added to the HUVECs and allowed to adhere for 15-30 minutes. The medium was changed every hour to avoid reinfection from the supernatant. At the indicated times (4 hours or 8 hours), monolayers were harvested and adherent bacteria counted. The number of internalized bacteria was determined by gentamicin protection assay, as described in Materials and Methods. Results are in Log CFU/ml.