Antibiofilm Effects of Azithromycin and Erythromycin on Porphyromonas gingivalis

Abstract

ABSTRACTAntibiotic resistance of biofilm-grown bacteria contributes to chronic infections, such as marginal and periapical periodontitis, which are strongly associated withPorphyromonas gingivalis. Concurrent azithromycin (AZM) administration and mechanical debridement improve the clinical parameters of periodontal tissuein situ. We examined thein vitroefficacy of AZM againstP. gingivalisbiofilms. The susceptibilities of adherentP. gingivalisstrains 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 adherentP. gingivaliscells 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 inhibitedP. gingivalisadherent 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 ofP. gingivalisbiofilms were significantly decreased by AZM at concentrations below the sub-MICs; however, ERY was not effective for inhibition ofP. gingivalisbiofilm cells at their sub-MICs. Furthermore, decreased density ofP. gingivalisbiofilms was observed three-dimensionally with sub-MIC AZM, using confocal laser scanning microscopy. These findings suggest that AZM is effective againstP. gingivalisbiofilms at sub-MIC levels and could have future clinical application for oral biofilm infections, such as chronic marginal and periapical periodontitis.