Description of a Multimetric Phytoplankton Index (MPI) for the assessment of transitional waters.

A Multimetric Phytoplankton Index (MPI) is proposed to support management policies for the assessment of transitional ecosystems and the implementation of the European Water Framework Directive. The MPI incorporates Hulburt's dominance index, bloom frequency and Menhinick's diversity index, calculated on the basis of phytoplankton species composition. Chlorophyll a concentrations were also included, to provide biomass data and to guarantee continuity and comparison with past evaluations. The MPI was calculated by averaging the ratios of the resulting values of each metric to those of a reference site characterised by low anthropogenic impact. The MPI was set up using data from over a 10-year period in several stations in Venice Lagoon (North-western Adriatic region), a highly valuable and heterogeneous transitional environment, subject to significant anthropogenic pressures. The dataset included physico-chemical data, nutrient and contaminant concentrations. Statistical analyses allowed us to gauge the MPI's responses to anthropogenic pressures and to verify its reliability.

Integrated evaluation of environmental parameters influencing Vibrio occurrence in the coastal Northern Adriatic Sea (Italy) facing the Venetian lagoon.

In the marine environment, the persistence and abundance of Vibrio are related to a number of environmental parameters. The influence of the different environmental variables in determining the Vibrio occurrence could be different in the specific geographic areas around the world. Moreover, oceanographic parameters are generally interdependent and should not be considered separately when their influence on bacterial presence and concentration is tested. In this study, an integrated approach was used to identify key parameters determining the abundance of Vibrio spp in marine samples from the Venetian Lagoon in Italy, which is an important area for fish farming and tourism. Multivariate techniques have been adopted to analyze the dataset: using PCA, it was shown that a relatively high proportion of the total variance in this area was mainly due to two independent variables, namely salinity and temperature. Using cluster analysis, it was possible to categorize different groups with homogeneous features as regards space ("stations") and time ("seasons") distribution, as well as to quantify the values of environmental variables and the Vibrio abundances in each category. Furthermore, integrating key environmental factors and bacterial concentration values, it was possible to identify levels of salinity and sea surface temperature which were optimal for Vibrio concentration in water, plankton, and sediment samples. The identification of key environmental variables conditioning Vibrio occurrence should facilitate ocean monitoring, making it possible to predict unexpected variations in marine microflora which determine possible public health risks in coastal areas.

Phytoplankton-bacterioplankton interactions and carbon fluxes through microbial communities in a microtidal lagoon.

The strength of the bacteria-phytoplankton coupling and the importance of the microbially mediated carbon fluxes have been investigated in a microtidal lagoon (Lagoon of Venice), with emphasis on the trophic variations, in a within-system perspective. The large trophic heterogeneity of the three stations considered corresponded to an elevated variability of phytoplankton biomass and production (from 0.1 up to 300 microg C L(-1) h(-1)), while bacteria standing stock and production (from 2 to 8 microg C L(-1) h(-1)) appeared, in comparison, to be much more constant. The relationships between bacteria and the phytoplankton community could not be related to the trophic state in a straightforward way; rather, some patterns common to the three stations could be evidenced. In particular, the two communities appeared to be clearly uncoupled, bacterial carbon demand (BCD) always exceeding dissolved primary production (DPP) and, mostly, also total primary production, independent of the station and the season considered. The occurrence of situations in which bacterial production was larger than primary production and the continuous prevalence of BCD over DPP implied that, quite independent of the trophic variability, sources of organic carbon other than phytoplankton production were necessary and available to sustain the bacterial metabolism in the Lagoon of Venice.

Drinking habits are associated with changes in the dental plaque microbial community.

Caries and gingivitis are the most prevalent oral infectious diseases of humans and are due to the accumulation of dental plaque (a microbial biofilm) on the tooth surface and at the gingival margin, respectively. Several in vitro and in vivo studies have shown that many natural components of foods and beverages inhibit the adhesion of and/or exert activity against oral bacteria. These biological activities have mainly been attributed to the polyphenol fraction. In order to explore the possibility that diet can alter the dental plaque community, in this study we evaluated the composition of the microbiota of supra- and subgingival plaque samples collected from 75 adult subjects with different drinking habits (drinkers of coffee, red wine, or water for at least 2 years) by analyzing the microbial population through the separation of PCR-amplified fragments using the denaturing gradient gel electrophoresis (DGGE) technique. The mean numbers of bands of the DGGE profiles from all three categories were evaluated. There were no significant differences between the two kinds of plaque collected from the control group (water drinkers), and this group showed the highest number of bands (supragingival plaque, 18.98 +/- 3.16 bands; subgingival plaque, 18.7 +/- 3.23 bands). The coffee and wine drinker groups generated the lowest numbers of bands for both supragingival plaque (coffee drinkers, 8.25 +/- 3.53 bands; wine drinkers, 7.93 +/- 2.55 bands) and subgingival plaque (coffee drinkers, 8.3 +/- 3.03 bands; wine drinkers, 7.65 +/- 1.68 bands). The differences between coffee drinkers or wine drinkers and the control group (water drinkers) were statistically significant. A total of 34 microorganisms were identified, and the frequency of their distribution in the three subject categories was analyzed. A greater percentage of subjects were positive for facultative aerobes when supragingival plaque was analyzed, while anaerobes were more frequent in subgingival plaque samples. It is noteworthy that the frequency of identification of anaerobes was significantly reduced when the frequencies for coffee and wine drinkers were compared with the frequencies for subjects in the control group. The DGGE profiles of the organisms in both plaque samples from all groups were generated and were used to construct dendrograms. A number of distinct clusters of organisms from water, coffee, and wine drinkers were formed. The clustering of some of the DGGE results into cohort-specific clusters implies similarities in the microbiotas within these groups and relevant differences in the microbiotas between cohorts. This supports the notion that the drinking habits of the subjects may influence the microbiota at both the supragingival and the subgingival levels.

Microbiological evaluation of the effects of hyperbaric oxygen on periodontal disease.

The term periodontitis indicates a variety of clinical manifestations of infectious disorders in which the supporting tissues of the teeth are attacked. The initiation and progression of periodontal disease are attributed to the presence of elevated levels of pathogenic bacteria within the gingival crevice. Approaches to periodontal treatment range from surgical to regenerative therapy and anti-infective chemotherapy. Anti-infective drug therapy should be rationally based on the composition of the pathogenic microbiota. It is also important to recognize that the periodontopathic plaque constitutes a bacterial biofilm infection that may render the resident microorganisms more resistant than the same organisms grown planktonically. Hyperbaric oxygen (HBO) has been successfully used in several medical applications. The therapeutic effect is related to elevated partial oxygen pressure in the tissues. The aim of this study was to evaluate the effects of HBO on a selected number of patients suffering from adult chronic periodontitis in comparison with surgical intervention (scaling and root planning, SRP), as well as the effects of a combination of both therapies on the evolution over time of the microflora of the periodontal pockets. Bacteria were detected either by culture or by a molecular method (PCR). Microbiological data indicate that the combination of HBO and SRP substantially reduced (by up to 99.9%) the gram-negative anaerobe loads of the subgingival microflora. The low values of pathogens persisted for at least two months after the therapy. HBO or SRP alone produced a temporarily more limited effect on periodontal anaerobes. Additional experimental confirmation of these results was provided by molecular detection of the main periodontopathogenic bacteria with a significant reduction in the number of dental sites which harboured them. It is also shown that HBO both alone and in combination with SRP reduced the Gingival Index value to zero and gingival health persisted for 3 months at least. Thus, in parallel with the loss of periodontopathogenic bacteria, a substantial improvement in oral health was observed. In conclusion, this study has shown that HBO may represent a useful aid, especially in combination with SRP, as far as non-surgical periodontal therapy is concerned.

Differences in microbiological composition of saliva and dental plaque in subjects with different drinking habits.

Several foods have been shown to contain natural components (especially polyphenols) which display anti-adhesive properties against Streptococcus mutans, the aetiological agent responsible for dental crown caries, as well as inhibition of glucosyltransferases, which are the S. mutans enzymes involved in the synthesis of an adherent, water-insoluble glucan from sucrose. Other studies have demonstrated an in vitro action on oral plaque biofilm formation and desorption. This study evaluated whether the activity displayed in vitro by food compounds could affect the microbiological composition of saliva and dental plaque of subjects with a diet rich in these foods, comparing the results with those obtained from subjects with a different diet. The foods considered were: coffee, barley coffee, tea and wine. A total of 93 subjects were recruited into the study. Six samples of both plaque and saliva were collected from each subject at roughly one-monthly intervals. Total bacteria, total streptococci, S. mutans and lactobacilli counts were determined by culture in both saliva and dental plaque. The highest bacterial titres were recorded for the control population, while each drinking habit subgroup showed counts roughly one log lower than the controls. These differences in bacterial counts proved statistically significant (P<0.05). As far as dental plaque was concerned, while total counts did not significantly vary per mg of plaque in the subjects belonging to the different drinking habit subgroups, a significant decrease (P<0.05) was observed in those subjects drinking coffee, tea, barley coffee and wine when mutans streptococci and lactobacilli were evaluated. In several cases a more than one log decrease was observed. Plaque indices were also determined, and a significant (P<0.05) reduction in values was recorded in the subjects belonging the specific drinking habit subgroups compared to the control group. This study indicates that there is a correlation between consumption of specific foods and oral health in terms of reduced plaque deposition and lower counts of odontopathogens.