Aquatic ecology of the oyster pathogens Vibrio splendidus and Vibrio aestuarianus.

The ecology of the oyster pathogens Vibrio splendidus and Vibrio aestuarianus in the brackish aquatic environment was extensively investigated in this study. By conducting laboratory experiments under natural setting conditions, it was shown that V. splendidus LGP32 strain generally exhibits longer persistence in both seawater and sediment than V. aestuarianus 01/32 strain. Both strains maintained viability and culturability for longer times in the sediment, suggesting that this compartment may represent a suitable niche for their persistence in the environment. In addition, both strains attached to chitin particles and copepods, the efficiency of attachment being higher in V. splendidus than in V. aestuarianus. Similarly, LGP32 strain showed a greater capability to form biofilm on poly-vinyl chloride (PVC) surfaces than 01/32 strain. LGP32 and 01/32 strains were also capable of entering a viable but non-culturable state after extended incubation at 5°C, a condition commonly found during cold season in the aquatic brackish environment. These results are consistent with field data collected during a 2-year sampling campaign in the northern Adriatic Sea and provide background information on the mechanisms promoting V. splendidus and V. aestuarianus persistence in coastal water, thus contributing to a better understanding of the epidemiology of the associated diseases.

In vitro assessment of shiitake mushroom (Lentinula edodes) extract for its antigingivitis activity.

Gingivitis is a preventable disease characterised by inflammation of the gums due to the buildup of a microbial biofilm at the gingival margin. It is implicated as a precursor to periodontitis, a much more serious problem which includes associated bone loss. Unfortunately, due to poor oral hygiene among the general population, gingivitis is prevalent and results in high treatment costs. Consequently, the option of treating gingivitis using functional foods, which promote oral health, is an attractive one. Medicinal mushrooms, including shiitake, have long been known for their immune system boosting as well as antimicrobial effects; however, they have not been employed in the treatment of oral disease. In the current study, the effectiveness of shiitake mushroom extract was compared to that of the active component in the leading gingivitis mouthwash, containing chlorhexidine, in an artificial mouth model (constant depth film fermenter). The total bacterial numbers as well as numbers of eight key taxa in the oral community were investigated over time using multiplex qPCR. The results indicated that shiitake mushroom extract lowered the numbers of some pathogenic taxa without affecting the taxa associated with health, unlike chlorhexidine which has a limited effect on all taxa.

The effects of fractions from shiitake mushroom on composition and cariogenicity of dental plaque microcosms in an in vitro caries model.

The aim of the current study was to investigate the anticariogenic potential of the (sub)fractions obtained from the edible mushroom shiitake (Lentinula edodes) in in vitro caries model. We used a modified constant depth film fermentor (CDFF) with pooled saliva as the inoculum and bovine dentin as a substratum. The test compounds were low molecular weight fraction (MLMW) of the shiitake extract and subfractions 4 and 5 (SF4 and SF5) of this fraction. Chlorhexidine (CHX) and water served as a positive and a negative control, respectively. Dentin mineral loss was quantified (TMR), microbial shifts within the microcosms were determined (qPCR), and the acidogenicity of the microcosms was assessed (CIA). From the compounds tested, the SF4 of shiitake showed strong inhibiting effect on dentin demineralization and induced microbial shifts that could be associated with oral health. The acid producing potential was increased, suggesting uncoupling of the glycolysis of the microbiota by the exposure to SF4. In conclusion, the results suggest that SF4 of shiitake has an anticariogenic potential.

Effects of fruit and vegetable low molecular mass fractions on gene expression in gingival cells challenged with Prevotella intermedia and Actinomyces naeslundii.

Low molecular mass (LMM) fractions obtained from extracts of raspberry, red chicory, and Shiitake mushrooms have been shown to be an useful source of specific antibacterial, antiadhesion/coaggregation, and antibiofilm agent(s) that might be used for protection towards caries and gingivitis. In this paper, the effects of such LMM fractions on human gingival KB cells exposed to the periodontal pathogens Prevotella intermedia and Actinomyces naeslundii were evaluated. Expression of cytokeratin 18 (CK18) and ß4 integrin (ß4INT) genes, that are involved in cell proliferation/differentiation and adhesion, and of the antimicrobial peptide ß2 defensin (HßD2) in KB cells was increased upon exposure to either live or heat-killed bacteria. All LMM fractions tested prevented or reduced the induction of gene expression by P. intermedia and A. naeslundii depending on the experimental conditions. Overall, the results suggested that LMM fractions could modulate the effects of bacteria associated with periodontal disease in gingival cells.

Inhibitory activity by barley coffee components towards Streptococcus mutans biofilm.

It was shown that barley coffee (BC) interferes with Streptococcus mutans adsorption to hydroxyapatite. After BC component fractionation by dialysis and gel filtration chromatography (GFC), it was found that the low molecular mass (<1,000 Da) fraction (LMM fraction) containing polyphenols, zinc and fluoride ions and, above all, a high molecular mass (HMM > 1,000 kDa) melanoidin fraction display strong anti-adhesive properties towards S. mutans. In this study, we have further examined the potential of BC, BC LMM fraction and BC HMM melanoidin fraction as caries controlling agents by evaluating their anti-biofilm activity.The effects of BC and BC fractions on biofilm formation by S. mutans ATCC 25175 and its detachment from pre-developed biofilms were evaluated by microtiter plate assay. It was found that BC and its fractions, at concentrations ranging from 60 to 15 mg ml(-1) that are devoid of antimicrobial activity, inhibited S. mutans biofilm formation. An increase of S. mutans ATCC 25175 detachment from 24 h developed biofilm was observed at the highest tested concentrations. Interestingly, BC and BC fractions also showed anti-biofilm activity towards a variety of S. mutans clinical strains isolated from saliva, plaque and caries lesions of adult donors. In general, the HMM melanoidin fraction was more active than the LMM fraction. These findings, classifying BC LMM fraction and BC HMM melanoidin fractions as natural anti-biofilm agents, represent the basis for studying their possible use as anti-caries agents.

Identification of organic acids in Cichorium intybus inhibiting virulence-related properties of oral pathogenic bacteria.

The low molecular mass (LMM) extract of Cichorium intybus var. silvestre (red chicory) has been shown to inhibit virulence-linked properties of oral pathogens including Streptococcus mutans, Actinomyces naeslundii and Prevotella intermedia. In the present study HPLC-DAD-ESI/MS(2) was used to investigate the compounds contained in this extract for their anti-virulence activity. The extract contained a number of components, including oxalic, succinic, shikimic and quinic acids, which interfere with the growth and virulence traits (i.e., biofilm formation, adherence to epithelial cells and hydroxyapatite) of oral pathogens involved in gingivitis and tooth decay. Succinic and quinic acid seem to be the most potent, mainly by interfering with the ability of oral pathogens to form biofilms (either through inhibition of their development or promotion of their disruption). Our findings suggest that one or more of these compounds may modulate plaque formation in vivo, which is a prerequisite for the development of both caries and gingivitis.

Functional foods and strategies contrasting bacterial adhesion.

Antibacterial strategies targeting bacterial adhesion to substrates are considered a valuable alternative to traditional antibiotic therapy, in view of the great advantage they bring in combating the infectious process at the very early stage without selecting for drug resistant cells. Amongst bioactive compounds with activity against bacterial adhesion, several are found in natural food and beverages, such as cranberry, tea, coffee, wine and milk. For the analysis of their anti-infective potential, successful experimental models can be conducted using different substrates from the oral cavity. Studies conducted so far in this field allowed the discovery of a variety of anti-adhesive fractions and compounds proven to be effective against bacterial traits involved in the development of oral pathologies such as caries and gingivitis/periodontitis. Discovering new anti-adhesive compounds from natural products, unravelling and testing their prophylactic and therapeutic values, and improving their use in the general population are promising new frontiers in the global fight against human infectious diseases.

Antiadhesion and antibiofilm activities of high molecular weight coffee components against Streptococcus mutans.

In previous studies we demonstrated that green and roasted coffee contains low molecular weight (LMW) compounds capable of inhibiting the ability of Streptococcus mutans, the major causative agent of human dental caries, to adhere to hydroxyapatite (HA) beads. This study addressed the ability of the whole high molecular weight coffee fraction (cHMW) and of its melanoidin and non-melanoidin components (GFC1-5), applied at concentrations that occur in coffee beverages, to (i) inhibit S. mutans growth; (ii) affect S. mutans sucrose-dependent adhesion to and detachment from saliva-coated HA beads (sHA); and (iii) inhibit biofilm development on microtiter plates. The results indicated that only cHMW is endowed with antimicrobial activity. The cHMW fraction and each of the five GFC components inhibited S. mutans adhesion, the strongest effect being exerted by cHMW (91%) and GFC1 (88%). S. mutans detachment from sHA was four times greater (∼20%) with cHMW and the GFC1 and GFC4 melanoidins than with controls. Finally, biofilm production by S. mutans was completely abolished by cHMW and was reduced by 20% by the melanoidin components GFC2 and GFC4 and by the non-melanoidin component GFC5 compared with controls. Altogether these findings show that coffee beverage contains both LMW compounds and HMW melanoidin and non-melanoidin components with a strong ability to interfere in vitro with the S. mutans traits relevant for cariogenesis.