Fig 2. Growth of Hb and Tf receptor mutants of N. meningitidis in whole human blood.

Bacterial strains (8047, MC58 and mutants thereof) were grown to mid-log (OD600 = ~ 0.6) in MHB supplemented with 20 μM CMP-NANA and then added to freshly-collected human blood. Cultures were incubated at 37°C, 5% CO₂ for 4 hours. Samples, collected from the inoculum and at 0, 60, 120, 180 and 240 minutes from blood cultures, were plated in duplicate onto supplemented BHI agar. The Fig shows a representative experiment. Each strain and mutant was tested in triplicate and intra-assay variation was measured by calculating the standard error of the mean of the CFU counts obtained at each timepoint. Blood samples were collected from two healthy MBL-deficient volunteers (V1 and V2) and an uncharacterised volunteer (V3). (A) strain 8047 (wt) in blood from V2 and V3, which was treated with either 5 mM or 10 mM EDTA; (B) wild-type and mutants of strain MC58 in untreated blood from V1; (C) wild-type and mutants of strain MC58 in untreated blood from V2.