The anti-adhesive mode of action of a purified mushroom (Lentinus edodes) extract with anticaries and antigingivitis properties in two oral bacterial phatogens.

BACKGROUND: In previous works we have shown that a low-molecular-mass (LMM) fraction from mushroom (Lentinus edodes) homogenate interferes with binding of Streptococcus mutans to hydroxyapatite and Prevotella intermedia to gingival cells. Additionally, inhibition of biofilm formation of both odonto- and periodonto-pathogenic bacteria and detachment from preformed biofilms have been described for this compound. Further purification of mushroom extract has been recently achieved and a sub-fraction (i.e. # 5) has been identified as containing the majority of the mentioned biological activities. The aim of this study was to characterise the bacterial receptors for the purified mushroom sub-fraction #5 in order to better elucidate the mode of action of this compound when interfering with bacterial adhesion to host surfaces or with bacteria-bacteria interactions in the biofilm state. METHODS: Candidate bacterial molecules to act as target of this compound were bacterial surface molecules involved in cell adhesion and biofilm formation, and, thus, we have considered cell wall associated proteins (CWPs), teichoic acid (TA) and lipoteichoic acid (LTA) of S. mutans, and outer membrane proteins (OMPs) and lipopolysaccharide (LPS) of P. intermedia. RESULTS: Fifteen S. mutans CWPs and TA were capable of binding sub-fraction #5, while LTA did not. As far as P. intermedia is concerned, we show that five OMPs interact with sub-fraction # 5. Capacity of binding to P. intermedia LPS was also studied but in this case negative results were obtained. CONCLUSIONS: Binding sub-fraction # 5 to surface molecules of S. mutans or P. intermedia may result in inactivation of their physiological functions. As a whole, these results indicate, at molecular level, the bacterial surface alterations affecting adhesion and biofim formation. For these antimicrobial properties, the compound may find use in daily oral hygiene.

Effects of mushroom and chicory extracts on the shape, physiology and proteome of the cariogenic bacterium Streptococcus mutans.

BACKGROUND: Dental caries is an infectious disease which results from the acidic demineralisation of the tooth enamel and dentine as a consequence of the dental plaque (a microbial biofilm) accumulation. Research showed that several foods contain some components with antibacterial and antiplaque activity. Previous studies indicated antimicrobial and antiplaque activities in a low-molecular-mass (LMM) fraction of extracts from either an edible mushroom (Lentinus edodes) or from Italian red chicory (Cichorium intybus). METHODS: We have evaluated the antimicrobial mode of action of these fractions on Streptococcus mutans, the etiological agent of human dental caries. The effects on shape, macromolecular syntheses and cell proteome were analysed. RESULTS: The best antimicrobial activity has been displayed by the LMM mushroom extract with a bacteriostatic effect. At the MIC of both extracts DNA synthesis was the main macromolecular synthesis inhibited, RNA synthesis was less inhibited than that of DNA and protein synthesis was inhibited only by roughly 50%. The partial inhibition of protein synthesis is compatible with the observed significant increase in cell mass. The increase in these parameters is linked to the morphological alteration with transition from cocci of the untreated control to elongated cells. Interestingly, these modifications were also observed at sub-MIC concentrations. Finally, membrane and cytosol proteome analysis was conducted under LMM mushroom extract treatment in comparison with untreated S. mutans cells. Significant changes were observed for 31 membrane proteins and 20 of the cytosol fractions. The possible role of the changed proteins is discussed. CONCLUSIONS: This report has shown an antibiotic-like mode of action of mushroom and chicory extracts as demonstrated by induced morphogenetic effects and inhibition of specific macromolecular synthesis. This feature as well as the safe use of this extract as result of its natural origin render the LMM both mushroom and chicory extracts suitable for the formulation into products for daily oral hygiene such as mouthwashes or toothpastes.

Effects of mushroom and chicory extracts on the physiology and shape of Prevotella intermedia, a periodontopathogenic bacterium.

Contrary to the common assumption that food has a negative impact on oral health, research has shown that several foods contain a number of components with antibacterial and antiplaque activity. These natural compounds may be useful for improving daily oral hygiene. In this study we evaluate the mode of antimicrobial action of fractions of mushroom and red chicory extracts on Prevotella intermedia, a periodontopathogenic bacterium. The minimal inhibitory concentration corresponded to 0.5x compared to the natural food concentration for both extracts. This concentration resulted in a bacteriostatic effect in mushroom extract and in a slightly bactericidal effect in chicory extract. Cell mass continued to increase even after division stopped. As regards macromolecular synthesis, DNA was almost totally inhibited upon addition of either mushroom or chicory extract, and RNA to a lesser extent, while protein synthesis continued. Cell elongation occurred after septum inhibition as documented by scanning electron microscopy and cell measurement. The morphogenetic effects are reminiscent of the mode of action of antibiotics such as quinolones or ß-lactams. The discovery of an antibiotic-like mode of action suggests that these extracts can be advantageously employed for daily oral hygiene in formulations of cosmetic products such as mouthwashes and toothpastes.