title: Antibiofilm effects of azithromycin and erythromycin on Porphyromonas gingivalis.
abstract: Antibiotic resistance of biofilm-grown bacteria contributes to chronic infections, such as marginal and periapical periodontitis, which are strongly associated with Porphyromonas gingivalis. Concurrent azithromycin (AZM) administration and mechanical debridement improve the clinical parameters of periodontal tissue in situ. We examined the in vitro efficacy of AZM against P. gingivalis biofilms. The susceptibilities of adherent P. gingivalis strains 381, HW24D1, 6/26, and W83 to AZM, erythromycin (ERY), ampicillin (AMP), ofloxacin (OFX), and gentamicin (GEN) were investigated using a static model. The optical densities of adherent P. gingivalis cells were significantly decreased by using AZM and ERY at sub-MIC levels compared with those of the controls in all the strains tested, except for the effect of ERY on strain W83. AMP and OFX inhibited P. gingivalis adherent cells at levels over their MICs, and GEN showed no inhibition in the static model. The effects of AZM and ERY against biofilm cells were investigated using a flow cell model. The ATP levels of P. gingivalis biofilms were significantly decreased by AZM at concentrations below the sub-MICs; however, ERY was not effective for inhibition of P. gingivalis biofilm cells at their sub-MICs. Furthermore, decreased density of P. gingivalis biofilms was observed three-dimensionally with sub-MIC AZM, using confocal laser scanning microscopy. These findings suggest that AZM is effective against P. gingivalis biofilms at sub-MIC levels and could have future clinical application for oral biofilm infections, such as chronic marginal and periapical periodontitis.
authors.affiliation: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.  noiri@dent.osaka-u.ac.jp.
authors.forename: H
authors.initials: H
authors.lastname: Maezono
authors.forename: Y
authors.initials: Y
authors.lastname: Noiri
authors.forename: Y
authors.initials: Y
authors.lastname: Asahi
authors.forename: M
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: R
authors.initials: R
authors.lastname: Yamamoto
authors.forename: N
authors.initials: N
authors.lastname: Izutani
authors.forename: H
authors.initials: H
authors.lastname: Azakami
authors.forename: S
authors.initials: S
authors.lastname: Ebisu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D004917:Erythromycin / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000592:standards; D018613:Microscopy, Confocal; D016966:Porphyromonas gingivalis / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D004917:Erythromycin; D017963:Azithromycin