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摘要
alpha-Mangostin (alpha MG) has been reported to be an effective antimicrobial agent against planktonic cells of Streptococcus mutans, a biofilm-forming and acid-producing cariogenic organism. However, its anti-biofilm activity remains to be determined. We examined whether alpha MG, a xanthone purified from Garcinia mangostana L grown in Vietnam, disrupts the development, acidogenicity, and/or the mechanical stability of S. mutans biofilms. Treatment regimens simulating those experienced clinically (twice-daily, 60 s exposure each) were used to assess the bioactivity of alpha MG using a saliva-coated hydroxyapatite (sHA) biofilm model. Topical applications of early-formed biofilms with alpha MG (150 mu M) effectively reduced further biomass accumulation and disrupted the 3D architecture of S. mutans biofilms. Biofilms treated with alpha MG had lower amounts of extracellular insoluble and intracellular iodophilic polysaccharides (30-45%) than those treated with vehicle control (P<0.05), while the number of viable bacterial counts was unaffected. Furthermore, alpha MG treatments significantly compromised the mechanical stability of the biofilm, facilitating its removal from the sHA surface when subjected to a constant shear stress of 0.809 N/m(2) (. 3-fold biofilm detachment from sHA vs. vehicle-treated biofilms; P<0.05). Moreover, acid production by S. mutans biofilms was disrupted following alpha MG treatments (vs. vehicle-control, P<0.05). The activity of enzymes associated with glucan synthesis, acid production, and acid tolerance (glucosyltransferases B and C, phosphotransferase-PTS system, and F1F0-ATPase) were significantly inhibited by alpha MG. The expression of manL, encoding a key component of the mannose PTS, and gtfB were slightly repressed by alpha MG treatment (P<0.05), while the expression of atpD (encoding F-ATPase) and gtfC genes was unaffected. Hence, this study reveals that brief exposures to alpha MG can disrupt the development and structural integrity of S. mutans biofilms, at least in part via inhibition of key enzymatic systems associated with exopolysaccharide synthesis and acidogenicity. alpha MG could be an effective anti-virulence additive for the control and/or removal of cariogenic biofilms.
- 出版日期2014-10-28
