Figure 2

Liquid broth assay results demonstrating the susceptibility of S. pneumoniae to lysozyme and the β defensins. Antibacterial liquid broth assays for the measurement of the activity of lysozyme (Lz) and β defensins-1 and -2 (HBD1 and HBD2), alone (A) and in combination (B) (Lz+HBD2), against S. pneumoniae 6B (Sp 6B). The combination of Lz and HBD1 was not tested. The combination of lysozyme (1000 μg/ml) and β defensin-2 (1 μg/ml or 2.5 μg/ml) was significantly more effective than lysozyme (1000 μg/ml), or β defensin-2 (1 μg/ml or 2.5 μg/ml) alone. (P = 0.008 and 0.005, respectively, for the difference in the effect of the Lz-HBD2 combinations versus Lz (1 mg/ml) alone. P= 0.0007 and 0.03 for the difference in the effect of the Lz-HBD2 combinations versus 2.5 μg/ml of β defensin-2 alone). Four concentrations (1 μg/ml, 2.5 μg/ml, 5 μg/ml and 10 μg) of human β defensin-2 (HBD-2) and one concentration (1 mg/ml) of lysozyme (Lz) were tested against the bacteria – either alone, or in combination.