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.