Antimicrobial susceptibility and virulence of Enterococcus spp. isolated from periodontitis-associated subgingival biofilm.

BACKGROUND: This study evaluated the prevalence, virulence and antimicrobial susceptibility of enterococci isolated from the subgingival microbiota of patients with different periodontal status. METHODS: Subgingival biofilm was obtained from individuals with periodontal health (PH) (n = 139), gingivitis (n = 103), and periodontitis (n = 305) and cultivated on selective media. Isolated strains were identified by mass spectrometry. Antimicrobial sensitivity was determined by disk diffusion, virulence genes by polymerase chain reaction, and the subgingival microbiota by checkerboard. Differences among groups were assessed by Kruskal-Wallis, Mann-Whitney, and Chi-square tests. RESULTS: Enterococcus spp. were isolated from 7.4% of all samples; 53.7% were Enterococcus faecalis. They were more prevalent in periodontitis (9.8%) and gingivitis (7.8%) than PH (2.2%; P <0.05), but no differences among stages of disease severity were observed. High rates of low susceptibility/resistance (>64%) to at least one antimicrobial were observed. Predominant virulence factors included ace (64.3%), asa (39.3%), and esp (35.7%). Fusobacterium nucleatum was prevalent in the subgingival microbiota of enterococci+ individuals, whereas Dialister pneumosintes was found in low frequency in patients with bopD+ enterococci. Oral streptococci were prevalent (>70%) in patients carrying enterococci susceptible to doxycycline (P <0.05), usually bopD- and esp- (P <0.01). CONCLUSIONS: E. faecalis is increased in periodontitis-associated biofilm. Oral enterococci carry virulence genes and express resistance to some antibiotics commonly used in dentistry, such as ciprofloxacin and erythromycin. Specific subgingival taxa are associated with oral enterococci, suggesting they may interact with species of the dysbiotic periodontitis biofilm, constituting a potential source of factors to tissue destruction, antibiotic resistance dissemination, and poor response to periodontal therapy.

Adsorption of chlorhexidine on synthetic hydroxyapatite and in vitro biological activity.

The kinetic of chlorhexidine digluconate (CHXDG) uptake from aqueous solution by hydroxyapatite (HA) was investigated by ultraviolet (UV) analysis performed in HA powder (UV-solid) after the CHX adsorption. Adsorption isotherm of chlorhexidine (CHX) uptake was modeled by a combination of Languimir and Langmuir-Freundlich mechanisms. Strong molecule-molecule interactions and positive cooperativity predominated in the surface when CHX concentration was above 8.6 µg(CHX)/mg(HA). UV-solid spectra (shape, intensity and band position) of CHX bound to HA revealed that long-range molecular structures, such as aggregates or micelles, started to be formed at low CHX concentrations (1.52 µg(CHX)/mg(HA)) and predominated at high concentrations. Grazing-incidence X-ray diffraction (GIXRD) analysis from synchrotron radiation discarded the formation of crystalline structures on HA surface or precipitation of CHX crystalline salts, as suggested in previous works. The effect of the HA/CHX association on HA in vitro bioactivity, cytotoxicity and CHX antimicrobial activity was evaluated. It was shown that CHX did not inhibit the precipitation of a poorly crystalline apatite at HA/CHX surface after soaking in simulating body fluid (SBF). Cell viability studies after exposure to extracts of HA and HA/CHX showed that both biomaterials did not present significant in vitro toxicity. Moreover, HA/CHX inhibited Enterococcus faecalis growth for up to 6 days, revealing that binding to HA did not affect antimicrobial activity of CHX and reduced bacterial adhesion. These results suggested that HA/CHX association could result in a potential adjuvant antimicrobial system for clinical use.

Effects of non-surgical mechanical therapy on the subgingival microbiota of Brazilians with untreated chronic periodontitis: 9-month results.

BACKGROUND: Mechanical periodontal therapy is the most common treatment of periodontal infections. It is directed primarily towards removing biofilm and calculus from the root surfaces, leading to ecological changes in the subgingival environment. Thus, the purpose of this study was to evaluate the effects of scaling and root planing (SRP) on the subgingival microbiota of Brazilian subjects with untreated chronic periodontitis over a 9-month period. METHODS: Twenty-five untreated chronic periodontitis patients (mean age 43 +/- 5 years; 20% smokers; 45% males) were selected from a Brazilian population. At baseline, probing depth (PD), clinical attachment level (CAL), visible supragingival biofilm (SB), bleeding on probing (BOP), and suppuration (SUP) were measured at six sites/tooth. Subgingival plaque samples were obtained from 10 sites with the deepest PD (> or =5 mm) of each subject and tested for the presence of 25 oral species by DNA probes and the checkerboard technique. Patients received full mouth SRP and oral hygiene instructions. Clinical and microbiological assessments were repeated at 3, 6, and 9 months after therapy. During this period, all patients received maintenance therapy, including supragingival prophylaxis and reinforcement in home care procedures. The clinical and microbiological parameters examined were computed for each subject and at each visit. Differences over time were sought using the Friedman test. RESULTS: Significant reductions in mean CAL and PD (P <0.01), percent of sites with SB (P <0.01), BOP and SUP (P <0.05) were observed during the course of the study. In general, microbial changes were more pronounced for the mean counts than for the frequency of the microorganisms, particularly at 3 months post-therapy. Significant reductions in prevalence and levels were observed for certain periodontal pathogens including P. gingivalis (P <0.05; P <0.01), T. forsythensis (P <0.01), C. rectus (P <0.01), and A. actinomycetemcomitans (P <0.01; P <0.05). Nevertheless, the frequency of A. actinomycetemcomitans increased to baseline values at 9 months after therapy. Treponema ssp. and Prevotella spp. showed a modest decrease in prevalence, whereas marked reductions in their levels were observed. In contrast, the frequency and counts of the suspected pathogens P. micros and F. nucleatum increased after treatment. Species considered beneficial including Actinomyces spp., some oral streptococci, and V. parvula increased in prevalence, although these two last species tended to return to baseline levels at 9 months. CONCLUSION: In Brazilians with untreated chronic periodontitis, SRP led to clinical improvement associated with a decrease of certain periodontal pathogens, and an increase of beneficial species for up to 9 months after therapy.