Functional Foods, a new approach in treatment and prevention of oral infections

Aim Current drug therapies against biofilm-mediated diseases e.g. periodontitis, caries, endodontic infection and peri-implantitis, are reaching their limits due the worrying emergence of bacteria drug resistance. This leads to care failure, decrease of quality life and cost increase. Facing the lack of alternative treatments, scientists are searching after natural compounds to help fighting the above mentioned diseases. To suit this purpose, Pistacia lentiscus, a plant growing in Mediterranean maquis and Lentinula edodes (Shiitake), an edible mushroom were selected. Preliminary studies have showed that extracts of these plants have an inhibitory action against oral pathogens. However, little is known if these substances interact with the biofilm formation in the oral cavity. The aim of the present study was therefore to test the efficacy of these extracts as a modulator of the oral biofilm growth in vitro. Methods Different bacterial species belonging to the Streptococci family were selected because they play a key-role in the formation of biofilm in the oral cavity or in other systemic affections. They were: S. hominis , S. intermedius, S. mitis, S. mutans, S. pyogenes, S. agalatiae, in addition we have used as control an oral probiotic strain S. salivarius K12. Pistacia lentiscus oil (LBO) (Mediflora, Cagliari, Italy) and an aqueous extract of Shiitake (Miconet-Pavia) 1/7 v/v, were studied as functional foods. The bacteria were cultivated in Schaedler broth and grown under 37°C and 5% of CO2 conditions in a particular bioreactor to mimic the oral cavity. The first step was to establish the antibiotic sensitivity expressed in terms of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) following the National Committee for Clinical Laboratory Standard protocols (NCCLS). These quantitative results are useful for predicting in the oral tissues (i.e periodontal pocket), the antimicrobial concentration that must be attained to insure the inhibition or kill the pathogen microbiota. The second step was to evaluate the minimal biofilm inhibitory concentration (MBIC). Each strain was exposed at different concentrations of extract, previously mixed with growth medium from ½ to 1/128, extract/liquid medium . After 4 days of incubation, the biofilm was evaluated by a staining method and expressed as 550 nm of absorbance . Results LBO and Shitake showed a different antimicrobial profile against oral Streptococcus spp. In fact only S. intermedius and S. mitis resulted sensitives to LBO (MIC = 25%, MCB < 50%). Despite by using the Shiitake all tested Streptococci resulted inhibits , MICs from 50% to 12.5 %. Only the probiotic strain S. salivarius was insensitive at these functional extracts . The experiments performed in vitro with a simulating oral biofilm bioreactor, showed that all extracts were able to inhibit the biofilm for all pathogens, except for the probiotic strain. The MBICs were comprised: (i) LBO from 25 to 3.1 % and (ii) Shiitake from 25 to 1.12%. These experiments suggesting a different mechanism of bacterial inhibition between these functional foods . Conclusions This opens new ways on the possible treatments of oral pathologies based on the modulation pathogens/probiotics with subsequent formation of an new physiological oral microbiota. Furthermore, being foods, these substances have limited side-effects and might be considered as potential candidates to support existing no surgical therapies