Figure 2

Growth curves of 23 isolates (representing each of the serotypes included in 23vPPS) following incubation in serum broth (SSI). 1 × 10³ CFU/ml (50 μl) were inoculated into 250 μl pre-warmed broth in a microtitre plate, and then incubated at 37°C in 5% CO₂. The optical density (OD 630 nm) was measured every 15 min for 18 h using a spectrophotometer.