Anne Aamdal Scheie

Prevalence of Peri‐Implantitis Related to Severity of the Disease With Different Degrees of Bone Loss

BACKGROUND Several measurements are combined to diagnose peri-implant disease, and different thresholds are used to describe the disease. The purpose of this study was to evaluate the prevalence of peri-implant disease and to apply different diagnostic thresholds to assess its prevalence in relation to severities of peri-implantitis with different degrees of bone loss. METHODS A total of 164 subjects with dental implants inserted at the Institute of Clinical Odontology, University of Oslo, between 1990 and 2005, were invited to join the project, and 109 subjects attended the examination (mean age: 43.8 years; range: 18 to 80 years). The mean functional loading time was 8.4 years (SD: 4.6 years). The participants were examined clinically and radiographically. The following aspects of disease were assessed to describe the peri-implant condition: detectable radiographic peri-implant bone loss and inflammation, the presence of bleeding on probing at a probing depth >or=4 or >or=6 mm, and radiographic peri-implant bone loss assessed at >or=2.0 and >or=3.0 mm. RESULTS Assessing peri-implantitis at different levels of severity yielded a substantial variance in prevalence (11.3% to 47.1%) in the present study population. CONCLUSION Peri-implant inflammation was a frequent finding with and without peri-implant bone loss.

Does the Wide Use of Quaternary Ammonium Compounds Enhance the Selection and Spread of Antimicrobial Resistance and Thus Threaten Our Health

Quaternary ammonium compounds (QACs) are widely used biocides that possess antimicrobial effect against a broad range of microorganisms. These compounds are used for numerous industrial purposes, water treatment, antifungal treatment in horticulture, as well as in pharmaceutical and everyday consumer products as preserving agents, foam boosters, and detergents. Resistance toward QACs is widespread among a diverse range of microorganisms and is facilitated by several mechanisms such as modifications in the membrane composition, expression of stress response and repair systems, or expression of efflux pump genes. Development of resistance in both pathogenic and nonpathogenic bacteria has been related to application in human medicine and the food industry. QACs in cosmetic products will inevitably come into intimate contact with the skin or mucosal linings in the mouth and thus are likely to add to the selection pressure toward more QAC-resistant microorganisms among the skin or mouth flora. There is increasing evidence of coresistance and cross-resistance between QACs and a range of other clinically important antibiotics and disinfectants. Use of QACs may have driven the fixation and spread of certain resistance cassette collectors (class 1 integrons), currently responsible for a major part of antimicrobial resistance in gram-negative bacteria. More indiscriminate use of QACs such as in cosmetic products may drive the selection of further new genetic elements that will aid in the persistence and spread of antimicrobial resistance and thus in limiting our treatment options for microbial infections.

DNA Binding-Uptake System: a Link between Cell-to-Cell Communication and Biofilm Formation

DNA has recently been described as a major structural component of the extracellular matrix in biofilms. In streptococci, the competence-stimulating peptide (CSP) cell-to-cell signal is involved in competence for genetic transformation, biofilm formation, and autolysis. Among the genes regulated in response to the CSP are those involved in binding and uptake of extracellular DNA. We show in this study that a functional DNA binding-uptake system is involved in biofilm formation. A comGB mutant of Streptococcus mutans deficient in DNA binding and uptake, but unaffected in signaling, showed reduced biofilm formation. During growth in the presence of DNase I, biofilm was reduced in the wild type to levels similar to those found with the comGB mutant, suggesting that DNA plays an important role in the wild-type biofilm formation. We also showed that growth in the presence of synthetic CSP promoted significant release of DNA, with similar levels in the wild type and in the comGB mutant. The importance of the DNA binding-uptake system in biofilm formation points to possible novel targets to fight infections.

Biofilm Mode of Growth of Streptococcus intermedius Favored by a Competence-Stimulating Signaling Peptide

Gram-positive and gram-negative bacteria use quorum sensing to coordinate population behavior. In several streptococci, quorum sensing mediated by competence-stimulating peptides (CSP) is associated with development of competence for transformation. We show here that a synthetic CSP favored the biofilm mode of growth of Streptococcus intermedius without affecting the rate of culture growth.

Furanones, potential agents for preventing Staphylococcus epidermidis biofilm infections?

OBJECTIVES Staphylococcus epidermidis is often associated with biofilm infections related to medical implants. The aim of the present study was to find furanones that decrease biofilm formation without irritative or genotoxic effects, or effects on S. epidermidis growth. METHODS After screening including bioluminescence and biofilm assays, 2 furanones out of 11 were chosen for further studies. MIC values of the two furanones were established to determine whether biofilm inhibition effects were ascribed to inhibition of bacterial growth. To further investigate interference with communication, the effect of the furanones was tested in the presence of the autoinducer-2 precursor (S)-4,5-dihydroxy-2,3-pentanedione. The furanones were tested for possible irritative effects by the Hens egg test chorioallantoic membrane procedure. Finally, potential genotoxic effects in mice were assessed by a membrane array, and effects on global gene expression were investigated by using a microarray representing 30,000 genes of the mouse genome. RESULTS From the bioluminescence assay, 4 furanones out of 11 were chosen for further biofilm analyses. Biofilm formation by S. epidermidis was significantly decreased by the four furanones tested at concentrations not affecting microbial growth. Two furanones were chosen for further studies: one that decreased biofilm statistically more than the others and one containing two bromo substituents. The two furanones were found to be non-irritative and non-genotoxic at the concentrations used. CONCLUSIONS Furanones may inhibit biofilm formation through interference with quorum sensing and thus represent promising agents for protecting surfaces from being colonized by S. epidermidis.

THE BIOFILM CONCEPT: CONSEQUENCES FOR FUTURE PROPHYLAXIS OF ORAL DISEASES?

Biofilm control is fundamental to oral health. Existing oral prophylactic measures, however, are insufficient. The main reason is probably because the micro-organisms involved organize into complex biofilm communities with features that differ from those of planktonic cells. Micro-organisms have traditionally been studied in the planktonic state. Conclusions drawn from many of these studies, therefore, need to be revalidated. Recent global approaches to the study of microbial gene expression and regulation in non-oral micro-organisms have shed light on two-component and quorum-sensing systems for the transduction of stimuli that allow for coordinated gene expression. We suggest interference with two-component and quorum-sensing systems as potential novel strategies for the prevention of oral diseases through control of oral biofilms. Information is still lacking, however, on the genetic regulation of oral biofilm formation. A better understanding of these processes is of considerable importance.

AI-2/LuxS Is Involved in Increased Biofilm Formation by Streptococcus intermedius in the Presence of Antibiotics

ABSTRACT Bacteria utilize quorum-sensing communication to organize their behavior by monitoring the concentration of bacterial signals, referred to as autoinducers (AIs). The widespread detection of AI-2 signals and its enzymatic synthase (LuxS) in bacteria suggests that AI-2 is an inter- and intraspecies communication signal. We have previously shown that antibiotic susceptibility is affected by AI-2 signaling in Streptococcus anginosus. Since chronic infections involve persistent biofilms resilient to antibiotic treatment, we explored the role of AI-2/LuxS in Streptococcus intermedius biofilm formation and cell viability when the organism was exposed to sub-MICs of ampicillin, ciprofloxacin, or tetracycline. The S. intermedius wild type (WT) and its isogenic luxS mutant, strain SI006, were exposed to sub-MICs of ampicillin, ciprofloxacin, or tetracycline. Biofilms were formed on polystyrene discs in microtiter plates. To assess planktonic cell viability, the ATP microbial viability assay was performed and the numbers of CFU were determined. For complementation assays, the AI-2 precursor dihydroxy pentanedione (DPD) was used as a supplement for SI006. Relative luxS expression was quantified by real-time PCR. The sub-MICs of all three antibiotics increased biofilm formation in S. intermedius WT. However, biofilm formation by SI006 was either unaffected or reduced (P ≤ 0.05). Bacterial viability tests of biofilm and planktonic cell cultures indicated that SI006 was more susceptible to antibiotics than the WT. DPD complemented the luxS mutant phenotype. Real-time PCR revealed modest yet significant changes in luxS expression in the presence of antibiotic concentrations that increased biofilm formation. In conclusion, in S. intermedius, AI-2/LuxS was involved in antibiotic susceptibility and increased biofilm formation at sub-MICs of antibiotic.

The association between selected risk indicators and severity of peri-implantitis using mixed model analyses.

AIM The aim of the study was to assess possible risk indicators for peri-implantitis at different levels of severity using multi-level analyses. MATERIAL AND METHODS One hundred and nine subjects attended the examination, 69 females and 40 males. Mean time of implants in function was 8.4 years (standard deviation 4.6) (subject level). The participants were examined clinically and radiographically. Information regarding general health and habits was gathered, with special emphasis on smoking, oral hygiene and susceptibility to periodontitis. The relation between possible risk indicators and the following features were assessed: • Detectable peri-implantitis: detectable radiographic bone loss (>0.4 mm) and inflammation • Overt peri-implantitis: radiographic peri-implant bone loss 2.0 mm and bleeding on probing /suppuration at pocket probing depth 4 mm. RESULTS Multi-level statistical analyses identified location in the maxilla as risk indicator for detectable peri-implantitis. Regarding overt peri-implantitis, gender (male) and history of periodontitis were identified as risk indicators. CONCLUSION Individuals with a history of periodontitis were prone to peri-implantitis, peri-implant bone loss ≥ 2.0 mm and overt in the present study. No association was found between smoking and peri-implant disease in the present study population.

Prevalence of Implant Loss and the Influence of Associated Factors

BACKGROUND The objective of this study was to assess the outcome of dental implants inserted at the Institute of Clinical Odontology, University of Oslo, between 1990 and 2005. The prevalence of implant loss and the factors associated with the outcome were studied. METHODS A total of 164 subjects were invited to participate in this cross-sectional project, of whom 55 were unable, leaving 109 volunteers available for examination. The study population included 69 females and 40 males with a mean age of 43.8 years at the time of implant insertion (range, 18 to 80 years). At the subject level, the mean time from implant loading to the present examination was 8.4 years (range, 1.1 to 16.0 years). The participants were examined clinically and radiographically and interviewed regarding general health and habits. RESULTS The 109 examined subjects had been treated with 374 implants. Eighteen implants (4.8%) were lost in 10 subjects (9.2%). Eleven implants were lost before loading, three were lost during the first 5 years after loading, and four were lost 5 to 10 years after loading. No implants were lost after >10 years of loading. The loss of oral implants was significantly associated with a history of smoking and periodontitis (P <0.05). CONCLUSIONS The inserted implants showed a high survival rate, especially after the first year of insertion, even though the subjects were not maintained by specialists. All late implant losses were preceded by an early loss. Implant loss was significantly associated with smoking and periodontitis.

Purification and functional studies of a potent modified quorum‐sensing peptide and a two‐peptide bacteriocin in Streptococcus mutans

Bacteria use quorum‐sensing signals or autoinducers to communicate. The signals in Gram‐positive bacteria are often peptides activated by proteolytic removal of an N‐terminal leader sequence. While investigating stimulation of antimicrobial peptide production by the Streptococcus mutans synthetic competence stimulating peptide signal (21‐CSP), we found a peptide similar to the 21‐CSP, but lacking the three C‐terminal amino acid residues (18‐CSP). The 18‐CSP was more potent in inducing competence, biofilm formation, and antimicrobial activity than the 21‐CSP. Our results indicate that cleavage of the three C‐terminal residues occurred post export, and was not regulated by the CSP‐signalling system. Deletion of comD encoding the CSP receptor abolished the competence and biofilm responses to the 21‐CSP and the 18‐CSP, suggesting that signal transduction via the ComD receptor is involved in the responses to both CSPs. In S. mutans GS5, beside the 18‐CSP we also purified to homogeneity a two‐peptide bacteriocin which production was stimulated by the 18‐CSP and the 21‐CSP. Partial sequence of the two‐peptide bacteriocin revealed the product of the smbAB genes recently described. We found that the peptide SmbB was slightly different from the deduced sequence, and confirmed the prediction that both peptides constituting SmbAB bacteriocin are post‐translationally modified. SmbAB exhibited antimicrobial activity against 11 species of streptococci, Enterococcus faecalis and Staphylocococcus epidermidis. Taken together, the findings support the involvement of the CSP response in bacteriocin production by streptococci and suggest a novel strategy to potentiate autoinducer activity.