MMP8 and infection: HBMEC were infected with both strains MC58 and MC58 siaD using different bacterial concentrations and MMP-8 activity was assayed at 2, 4, 8, and 24 h p.i. As shown in Figure 5, infection of HBMEC with both strains induced a time and dose-dependent secretion of active MMP-8 in the supernatant.