Relative effectiveness of azithromycin in killing intracellular Porphyromonas gingivalis

• Published in: Clinical and experimental dental research 2016-06, Vol.2 (1), p.35-43
• Main Authors: Lai, Pin‐Chuang, Walters, John D.
• Format: Article
• Language: English
• Subjects: Antibiotics; Antimicrobial agents; Bacteria; Fibroblasts; Gum disease; Immune system; invasive microorganisms; Laboratories; Original; periodontitis; pharmacokinetics; Studies
• ISSN: 2057-4347; 2057-4347
• DOI: 10.1002/cre2.17

Invasive infections by Porphyromonas gingivalis are associated with persistent periodontal attachment loss and can be difficult to eliminate by scaling and root planing. Azithromycin (AZM) inhibits P. gingivalis and is actively accumulated by most human cells. We used an in vitro infection model to compare the effectiveness of AZM in killing intracellular P. gingivalis to the combined regimen of amoxicillin (AMX) and metronidazole (MET). Transport of [3H]‐AZM by human gingival fibroblasts was characterized. Monolayers of Smulow–Glickman gingival epithelial cells or gingival fibroblasts were infected with P. gingivalis (strain 33277 or W83). After extracellular bacteria were eliminated with teicoplanin, infected cells were treated with therapeutic concentrations of AZM, AMX, or AMX + MET. Viable intracellular bacteria were released by cell lysis and plated on blood agar for enumeration. Antimicrobial activity against planktonic P. gingivalis was also evaluated. While survival of intraepithelial P. gingivalis 33277 was not significantly different after treatment with the three regimens, survival in infected fibroblasts was significantly lower after AZM treatment (65.9 ± 5.5%) compared with AMX (92.2 ± 3.5%) or AMX + MET (79.8 ± 5.2%, P