Y Asahi

Publications (3)8.86 Total impact

• Article: Synergistic effects of antibiotics and an N-acyl homoserine lactone analog on Porphyromonas gingivalis biofilms.

  Y Asahi, Y Noiri, J Igarashi, H Suga, H Azakami, S Ebisu
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  ABSTRACT: To investigate the effects of the combined application of an N-acyl homoserine lactone (HSL) analog and antibiotics on biofilms of Porphyromonas gingivalis, a major pathogen of periodontal disease. Antibiotics used were cefuroxime, ofloxacin and minocycline. A flow-cell model was used for biofilm formation. Samples were divided into four groups: control, analog-treated, antibiotic-treated and combined application groups. Biofilm cell survival was determined using adenosine triphosphate (ATP) bioluminescence and confocal laser microscopy (CLSM). In the combined application group, the ATP count in biofilm cells was significantly decreased compared with the antibiotic-treated group (Games-Howell test, P < 0·05). A combination of cefuroxime and the analog was most effective against the P. gingivalis biofilm. CLSM observations revealed that the proportion of dead cells was highest in the combined application group. The combined application of the N-acyl HSL analog and antibiotics was effective at reducing the viability of P. gingivalis cells in biofilms. The combined application of the N-acyl HSL analog and antibiotics may be successful for eradicating infections involving bacterial biofilms, such as periodontitis.
  Journal of Applied Microbiology 11/2011; 112(2):404-11. · 2.34 Impact Factor
• Article: Antibiofilm effects of azithromycin and erythromycin on Porphyromonas gingivalis.

  H Maezono, Y Noiri, Y Asahi, M Yamaguchi, R Yamamoto, N Izutani, H Azakami, S Ebisu
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  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.
  Antimicrobial Agents and Chemotherapy 09/2011; 55(12):5887-92. · 4.84 Impact Factor
• Article: Effects of N-acyl homoserine lactone analogues on Porphyromonas gingivalis biofilm formation.

  Y Asahi, Y Noiri, J Igarashi, H Asai, H Suga, S Ebisu
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  ABSTRACT: The gram-negative anaerobic rod Porphyromonas gingivalis in oral biofilms is a primary etiological agent of periodontal disease. Biofilm formation of various gram-negative bacteria is regulated by a quorum-sensing circuit that relies on N-acyl homoserine lactones (HSLs). Some synthetic N-acyl HSL analogues act as quorum-sensing inhibitors and suppress biofilm formation in Pseudomonas aeruginosa. Development of chemical control agents against oral biofilms is necessary, because until now, biofilms have been removed only by mechanical debridement. The present study investigated the effect of N-acyl HSL analogues on P. gingivalis biofilm formation, with the aim of developing new drugs that inhibit oral biofilm formation. A flow-cell model was used for P. gingivalis biofilm formation. Seventeen synthetic N-acyl HSL analogues were quantitatively assessed by spectrophotometry. The effects of three antagonistic compounds against P. gingivalis biofilm formation were further examined by confocal laser scanning microscopy, and investigated for primary attachment using spectrophotometry and phase contrast microscopy. Ten out of 17 analogues affected P. gingivalis biofilm formation. Three out of 10 analogues significantly decreased biofilm-forming cells (p < 0.05), and these biofilm structures were less well formed three-dimensionally. There were no quantitative or qualitative differences in cell attachment between the control and the three analogue-treated groups. Three synthetic N-acyl HSL analogues inhibited biofilm formation in P. gingivalis. We suggest that these analogues influence the development stage of P. gingivalis biofilm formation.
  Journal of Periodontal Research 09/2009; 45(2):255-61. · 1.69 Impact Factor