Figure 4.

Blood agar colonies (CFU of P. gingivalis) that gave an indication of the efficacy of the porphyrin compound. (a) A negative control blood agar plate indicating no contamination. (b) Strong growth from the intracellular and adherent P. gingivalis culture for 1.5 h. (c, d) Invaded P. gingivalis treated with metronidazole (20 or 200 μg·mL⁻¹) and gentamycin (30 or 300 μg·mL⁻¹) for an additional 1 h, respectively, to compare whether there was any differences in killing adherent (extracellular) bacterial cells. Adherent/extracellular (surface-bound) bacteria were only eliminated with a combination of high levels of metronidazole (200 μg·mL⁻¹) and gentamycin (300 μg·mL⁻¹) (d). This represented intracellular infection of P. gingivalis. (e, f) Representative of cells treated with antibiotics and porphyrin compound or porphyrin compound only, for up to 4 and 6 h. All bacteria were eliminated. Panels (g–i) showed 6 h incubations with different treatments of P. gingivalis and antibiotics as controls. Bacteria were similar amounts with early time treatments (b–d), respectively. (j) The summary of the average counting numbers of intracellular P. gingivalis colonies (CFU) from blood agar cultures (a–f) at 4 days. CFU, colony forming units.