Julia Davies | Malmö University (original) (raw)
Papers by Julia Davies
BMC Oral Health
Background Caries and periodontitis are amongst the most prevalent diseases worldwide, leading to... more Background Caries and periodontitis are amongst the most prevalent diseases worldwide, leading to pain and loss of oral function for those affected. Prevention relies heavily on mechanical removal of dental plaque biofilms but for populations where this is not achievable, alternative plaque control methods are required. With concerns over undesirable side-effects and potential bacterial resistance due to the use of chlorhexidine gluconate (CHX), new antimicrobial substances for oral use are greatly needed. Here we have investigated the antimicrobial effect of hypochlorous acid (HOCl), stabilized with acetic acid (HAc), on oral biofilms and compared it to that of CHX. Possible adverse effects of stabilized HOCl on hydroxyapatite surfaces were also examined. Methods Single- and mixed-species biofilms of six common oral bacteria (Streptococcus mutans, Streptococcus gordonii, Actinomyces odontolyticus, Veillonella parvula, Parvimonas micra and Porphyromonas gingivalis) within a flow-cel...
Background Dysbiosis in subgingival microbial communities, resulting from increased inflammatory ... more Background Dysbiosis in subgingival microbial communities, resulting from increased inflammatory transudate from the gingival tissues, is an important factor in initiation and development of periodontitis. Dysbiotic communities are characterized by increased numbers of bacteria that exploit the serum-like transudate for nutrients, giving rise to a proteolytic community phenotype. Here we investigate the contribution of interactions between members of a sub-gingival community to survival and development of virulence in a serum environment - modelling that in the subgingival pocket. Methods Growth and proteolytic activity of three P. gingivalis strains in nutrient-rich broth or a serum environment were assessed using A600 and a fluorescent protease substrate, respectively. Adherence of P. gingivalis strains to serum-coated surfaces was studied with confocal microscopy and 2D-gel electrophoresis of bacterial supernatants used to investigate extracellular proteins. A model multi-species...
mSphere, 2019
Discovered over a half-century ago, lipoteichoic acid (LTA) is an abundant polymer found on the s... more Discovered over a half-century ago, lipoteichoic acid (LTA) is an abundant polymer found on the surface of Gram-positive bacteria. Although LTA is essential for the survival of many Gram-positive species, knowledge of how LTA contributes to bacterial physiology has remained elusive. Recently, LTA-deficient strains have been generated in some Gram-positive species, including the human oral commensal Streptococcus gordonii . The significance of our research is that we utilized an LTA-deficient strain of S. gordonii to address why LTA is physiologically important to Gram-positive bacteria. We demonstrate that in S. gordonii , LTA plays an important role in the presentation of many cell surface-associated proteins, contributing to cell envelope homeostasis, cell-to-cell interactions in biofilms, and adhesion to eukaryotic cells. These data may broadly reflect a physiological role of LTA in Gram-positive bacteria.
European Journal of Dental Education, 2020
The COVID‐19 pandemic has had an immediate and dramatic impact on dental education. The Associati... more The COVID‐19 pandemic has had an immediate and dramatic impact on dental education. The Association of Dental Education in Europe decided to carry out an investigation to assess the immediate response of European Academic Dental Institutions. An online survey was sent to both member and non‐member dental schools to investigate the impact on non‐clinical and clinical education, assessment and the well‐being/pastoral care measures implemented. The preliminary findings and discussion are presented in this paper, for the responses collected between the 25 March and 5 April 2020. The survey at this time of publication is ongoing, and detailed results can be accessed https://adee.org/covid‐19‐european‐dental‐education%E2%80%99s‐immediate‐response.
Bioscience Reports, 2019
There is a strong association between periodontal disease and atherosclerotic cardiovascular diso... more There is a strong association between periodontal disease and atherosclerotic cardiovascular disorders. A key event in the development of atherosclerosis is accumulation of modified lipoproteins within the arterial wall. We hypothesise that patients with periodontitis have an altered lipoprotein profile towards an atherogenic form. Therefore, the present study aims at identifying modifications of plasma lipoproteins in periodontitis. Lipoproteins from ten female patients with periodontitis and gender- and age-matched healthy controls were isolated by density-gradient ultracentrifugation. Proteins were separated by 2D gel-electrophoresis and identified by map-matching or by nano-LC followed by MS. Apolipoprotein (Apo) A-I (ApoA-I) methionine oxidation, Oxyblot, total antioxidant capacity and a multiplex of 71 inflammation-related plasma proteins were assessed. Reduced levels of apoJ, phospholipid transfer protein, apoF, complement C3, paraoxonase 3 and increased levels of α-1-antichy...
European Journal of Dental Education, 2017
It is often the case that good teachers just "intuitively" know how to teach. Whilst that may be ... more It is often the case that good teachers just "intuitively" know how to teach. Whilst that may be true, there is now a greater need to understand the various processes that underpin both the ways in which a curriculum is delivered, and the way in which the students engage with learning; curricula need to be designed to meet the changing needs of our new graduates, providing new, and robust learning opportunities, and be communicated effectively to both staff and students. The aim of this document is to draw together robust and contemporaneous methods of teaching, learning and assessment that help to overcome some of the more traditional barriers within dental undergraduate programmes. The methods have been chosen to map specifically to The Graduating European Dentist, and should be considered in parallel with the benchmarking process that educators and institutions employ locally.
European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, Jan 7, 2018
Post-operative infections are relatively common after posterior spine surgery, and there are seve... more Post-operative infections are relatively common after posterior spine surgery, and there are several observations reflecting different infection complications related to various metals implanted. Here, we selected an array of different bacterial species that are often found in infections associated with orthopaedic implants and tested for inhibition by hydrogen peroxide-treated titanium (Ti-peroxy). To study the possibility of using Ti-peroxy as an antimicrobial prophylaxis, we developed a protocol for standardized susceptibility testing of bacteria. Importantly, we found that the resulting Ti-peroxy was highly antimicrobial against all aerobic species tested, among others, Staphylococcus aureus and Pseudomonas aeruginosa. Proteus mirabilis was slightly more resistant than, for example, Klebsiella pneumoniae and enterococci. In contrast, anaerobic bacteria Cutibacterium acnes and Parvimonas micra were equally susceptible compared to staphylococci. Our findings suggest that the Ti-pe...
BMC Microbiology, 2017
Background: The ecological plaque hypothesis explains caries development as the result of the enr... more Background: The ecological plaque hypothesis explains caries development as the result of the enrichment of acid tolerant bacteria in dental biofilms in response to prolonged periods of low pH. Acid production by an acid tolerant microflora causes demineralisation of tooth enamel and thus, individuals with a greater proportion of acid tolerant bacteria would be expected to be more prone to caries development. Biofilm acid tolerance could therefore be a possible biomarker for caries prediction. However, little is known about the stability of biofilm acid tolerance over time in vivo or the distribution throughout the oral cavity. Therefore the aim of this study was to assess intra-individual differences in biofilm acid-tolerance between different tooth surfaces and inter-individual variation as well as stability of acid tolerance over time. Results: The majority of the adolescents showed low scores for biofilm acid tolerance. In 14 of 20 individuals no differences were seen between the three tooth sites examined. In the remaining six, acid-tolerance at the premolar site differed from one of the other sites. At 51 of 60 tooth sites, acid-tolerance at baseline was unchanged after 1 month. However, acid tolerance values changed over a 1-year period in 50% of the individuals. Conclusions: Biofilm acid tolerance showed short-term stability and low variation between different sites in the same individual suggesting that the acid tolerance could be a promising biological biomarker candidate for caries prediction. Further evaluation is however needed and prospective clinical trials are called for to evaluate the diagnostic accuracy.
The open dentistry journal, 2015
To develop a model in which to investigate the architecture of plaque biofilms formed on enamel s... more To develop a model in which to investigate the architecture of plaque biofilms formed on enamel surfaces in vivo and to compare the effects of anti-microbial agents of relevance for caries on biofilm vitality. Materials and Methodology : Enamel discs mounted on healing abutments in the pre-molar region were worn by three subjects for 7 days. Control discs were removed before subjects rinsed with 0.1% chlorhexidine digluconate (CHX) or 0.2% sodium fluoride (NaF) for 1 minute. Biofilms were stained with Baclight Live/Dead and z-stacks of images created using confocal scanning laser micoscopy. The levels of vital and dead/damaged bacteria in the biofilms, assessed as the proportion of green and red pixels respectively, were analysed using ImageTrak(®) software. Results : The subjects showed individual differences in biofilm architecture. The thickness of the biofilms varied from 28-96µm although cell density was always the greatest in the middle layers. In control biofilms, the overall...
Microbiology (Reading, England), 2009
Surface adhesion plays an essential part in the survival of the commensal organism Streptococcus ... more Surface adhesion plays an essential part in the survival of the commensal organism Streptococcus gordonii in the oral cavity as well as during opportunistic infections such as endocarditis. At least two types of cell surface protein involved in adhesion are found on the surface of Gram-positive bacteria: those anchored via an LPXTG motif by the enzyme sortase A (SrtA) and those associated with the cell surface by, as yet, unknown mechanisms. In srtA(-) mutants, LPXTG-containing proteins have been shown to be released rather than cross-linked to the cell wall. We have therefore used 2D gel electrophoresis of released proteins from an srtA(-) mutant as well as the wild-type strain, followed by peptide identification by MS, to identify a set of novel proteins predicted to be present on the surface of S. gordonii DL1. This includes two large LPXTG-linked proteins (SGO_0707 and SGO_1487), which both contain tandemly repeated sequences similar to those present in known fibrillar adhesins....
BMC Oral Health, 2014
Background: A key element for long-term success of dental implants is integration of the implant ... more Background: A key element for long-term success of dental implants is integration of the implant surface with the surrounding host tissues. Modification of titanium implant surfaces can enhance osteoblast activity but their effects on soft-tissue cells are unclear. Adherence of human keratinocytes and gingival fibroblasts to control commercially pure titanium (CpTi) and two surfaces prepared by anodic oxidation was therefore investigated. Since implant abutments are exposed to a bacteria-rich environment in vivo, the effect of oral bacteria on keratinocyte adhesion was also evaluated. Methods: The surfaces were characterized using scanning electron microscopy (SEM). The number of adhered cells and binding strength, as well as vitality of fibroblasts and keratinocytes were evaluated using confocal scanning laser microscopy after staining with Live/Dead Baclight. To evaluate the effect of bacteria on adherence and vitality, keratinocytes were co-cultured with a four-species streptococcal consortium. Results: SEM analysis showed the two anodically oxidized surfaces to be nano-structured with differing degrees of pore-density. Over 24 hours, both fibroblasts and keratinocytes adhered well to the nano-structured surfaces, although to a somewhat lesser degree than to CpTi (range 42-89% of the levels on CpTi). The strength of keratinocyte adhesion was greater than that of the fibroblasts but no differences in adhesion strength could be observed between the two nano-structured surfaces and the CpTi. The consortium of commensal streptococci markedly reduced keratinocyte adherence on all the surfaces as well as compromising membrane integrity of the adhered cells. Conclusion: Both the vitality and level of adherence of soft-tissue cells to the nano-structured surfaces was similar to that on CpTi. Co-culture with streptococci reduced the number of keratinocytes on all the surfaces to approximately the same level and caused cell damage, suggesting that commensal bacteria could affect adherence of soft-tissue cells to abutment surfaces in vivo.
Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis, 2012
♦Background Peritonitis is the leading cause of morbidity for peritoneal dialysis (PD) patients, ... more ♦Background Peritonitis is the leading cause of morbidity for peritoneal dialysis (PD) patients, and microbial biofilms have previously been identified on catheters from infected patients. However, few studies of catheters from patients without clinical signs of infection have been undertaken. The aim of the present study was to investigate the extent to which bacteria are present on catheters from PD patients with no symptoms of infection. ♦Methods Microbiologic culturing under aerobic and anaerobic conditions and confocal laser scanning microscopy were used to determine the distribution of bacteria on PD catheters from 15 patients without clinical signs of infection and on catheters from 2 infected patients. The 16S rRNA gene sequencing technique was used to identify cultured bacteria. ♦Results Bacteria were detected on 12 of the 15 catheters from patients without signs of infection and on the 2 catheters from infected patients. Single-species and mixed-microbial communities conta...
Microbiology, 2011
The use of dental implants to treat tooth loss has increased rapidly over recent years. 'Smooth' ... more The use of dental implants to treat tooth loss has increased rapidly over recent years. 'Smooth' implants showing high long-term success rates have successively been replaced by implants with rougher surfaces, designed to stimulate rapid osseointegration and promote tissue healing. If exposed in the oral cavity, rougher surfaces may promote bacterial adhesion leading to formation of microbial biofilms which can induce peri-implant inflammation. Streptococcus oralis is an early colonizer of oral surfaces and has been recovered from titanium surfaces in vivo. The purpose of this study was to examine the adherence of clinical strains of S. oralis to titanium with smooth or moderately rough surface topography and to determine the effect of a saliva-or serum-derived coating on this process. Adherence was studied using a flow-cell system with confocal laser scanning microscopy, while putative adhesins were analysed using proteomics of bacterial cell wall proteins. This showed that adherence to moderately rough surfaces was greater than to smooth surfaces. Serum did not promote binding of any of the studied S. oralis strains to titanium, whereas a saliva coating increased adherence in two of three strains tested. The higher level of adherence to the moderately rough surfaces was maintained even in the presence of a saliva coating. The S. oralis strains that bound to saliva expressed an LPXTG-linked protein which was not present in the non-adherent strain. Thus strains of S. oralis differ in their capacity to bind to saliva-coated titanium and we propose that this is due to differential expression of a novel adhesin. Abbreviations: 2DE, 2D electrophoresis; CLSM, confocal laser scanning microscopy; LC-MS/MS, liquid chromatography-tandem mass spectroscopy; S a , average height deviation; S ds , density of summits; S dr , developed interfacial area ratio.
FEMS Immunology & Medical Microbiology, 2010
Pseudomonas aeruginosa and Staphylococcus epidermidis are common opportunistic pathogens associat... more Pseudomonas aeruginosa and Staphylococcus epidermidis are common opportunistic pathogens associated with medical device-related biofilm infections. 16S rRNA-FISH and confocal laser scanning microscopy were used to study these two bacteria in dual-species biofilms. Two of the four S. epidermidis strains used were shown to form biofilms more avidly on polymer surfaces than the other two strains. In dualspecies biofilms, the presence of P. aeruginosa reduced biofilm formation by S. epidermidis, although different clinical isolates differed in their susceptibility to this effect. The most resistant isolate coexisted with P. aeruginosa for up to 18 h and was also resistant to the effects of the culture supernatant from P. aeruginosa biofilms, which caused dispersal from established biofilms of other S. epidermidis strains. Thus, different strains of S. epidermidis differed in their capacity to withstand the action of P. aeruginosa, with some being better equipped than others to coexist in biofilms with P. aeruginosa. Our data suggest that where S. epidermidis and P. aeruginosa are present on abiotic surfaces such as medical devices, S. epidermidis biofilm formation can be inhibited by P. aeruginosa through two mechanisms: disruption by extracellular products, possibly polysaccharides, and, in the later stages, by cell lysis.
BMC Oral Health, 2013
Background Titanium implants in the oral cavity are covered with a saliva-derived pellicle to whi... more Background Titanium implants in the oral cavity are covered with a saliva-derived pellicle to which early colonizing microorganisms such as Streptococcus oralis can bind. The protein profiles of salivary pellicles on titanium have not been well characterized and the proteins of importance for binding are thus unknown. Biofilm bacteria exhibit different phenotypes from their planktonic counterparts and contact with salivary proteins may be one factor contributing to the induction of changes in physiology. We have characterized salivary pellicles from titanium surfaces and investigated how contact with uncoated and saliva-coated titanium surfaces affects metabolic activity in adherent cells of S. oralis. Methods Salivary pellicles on smooth titanium surfaces were desorbed and these, as well as purified human saliva, were subjected to two-dimensional gel electrophoresis and mass spectroscopy. A parallel plate flow-cell model was used to study binding of a fresh isolate of S. oralis to ...
BMC Oral Health, 2013
BackgroundMucosal surfaces are coated with layers of mucus gel that protect the underlying tissue... more BackgroundMucosal surfaces are coated with layers of mucus gel that protect the underlying tissues and promote colonization by members of the commensal microflora.Lactobacillus fermentumis a common inhabitant of the oral cavity, gastrointestinal and reproductive tracts and is one of the most important lactic acid bacteria contributing to the formation of a healthy intestinal microflora. We have investigated the proteolytic activity inL. fermentumin response to interactions with the MUC5B mucin, which is a major component of mucus gels at sites colonized by this micro-organism.MethodsBiofilms ofLactobacillus fermentumwere established in mini-flow cells in the presence or absence of human salivary MUC5B. The proteolytic activity of biofilm cells was examined in a confocal scanning laser microscope with a fluorescent protease substrate. Degradation of MUC5B byL. fermentumwas analysed using SDS-PAGE followed by Western blotting with antisera raised against the MUC5B peptide. Cell surfac...
BMC Oral Health, 2011
Background The soft tissue around dental implants forms a barrier between the oral environment an... more Background The soft tissue around dental implants forms a barrier between the oral environment and the peri-implant bone and a crucial factor for long-term success of therapy is development of a good abutment/soft-tissue seal. Sol-gel derived nanoporous TiO2 coatings have been shown to enhance soft-tissue attachment but their effect on adhesion and biofilm formation by oral bacteria is unknown. Methods We have investigated how the properties of surfaces that may be used on abutments: turned titanium, sol-gel nanoporous TiO2 coated surfaces and anodized Ca2+ modified surfaces, affect biofilm formation by two early colonizers of the oral cavity: Streptococcus sanguinis and Actinomyces naeslundii. The bacteria were detected using 16S rRNA fluorescence in situ hybridization together with confocal laser scanning microscopy. Results Interferometry and atomic force microscopy revealed all the surfaces to be smooth (Sa ≤ 0.22 μm). Incubation with a consortium of S. sanguinis and A. naeslund...
Biochemical and Biophysical Research Communications, 1999
... Enrico Di Stasio a , 1 , Francesca Sciandra a , 1 , Bruno Maras b , Francesca Di Tommaso a , ... more ... Enrico Di Stasio a , 1 , Francesca Sciandra a , 1 , Bruno Maras b , Francesca Di Tommaso a , Tamara C. Petrucci c , Bruno Giardina a and Andrea Brancaccio a , 2. ... 12. SH Gee, RW Blacher, PJ Douville, PR Provost, PD Yurchenco and S. Carbonetto. J. Biol. Chem. ...
European Journal of Public Health, 2020
The prevalence and burden of untreated oral diseases throughout the life course remains high worl... more The prevalence and burden of untreated oral diseases throughout the life course remains high worldwide, and inequalities in oral health and dental care are increasing. This is a major public health issue that is not being enough addressed by the health care systems. To better manage populations' oral health, oral health professionals must be trained to adapt to population needs and societal and technological changes. Furthermore, dental institutions must fulfill their social responsibility by prioritizing educational and research activities that promote advancing individual and community health. In Europe, great variability exists between dental programs within the same country or between countries. This variability is an issue as European graduates can practice around the European Union through mutual recognition of their qualifications. This might lead to inequities in the availability, accessibility, acceptability and quality of health services. The convergence of competencie...
BMC Oral Health
Background Caries and periodontitis are amongst the most prevalent diseases worldwide, leading to... more Background Caries and periodontitis are amongst the most prevalent diseases worldwide, leading to pain and loss of oral function for those affected. Prevention relies heavily on mechanical removal of dental plaque biofilms but for populations where this is not achievable, alternative plaque control methods are required. With concerns over undesirable side-effects and potential bacterial resistance due to the use of chlorhexidine gluconate (CHX), new antimicrobial substances for oral use are greatly needed. Here we have investigated the antimicrobial effect of hypochlorous acid (HOCl), stabilized with acetic acid (HAc), on oral biofilms and compared it to that of CHX. Possible adverse effects of stabilized HOCl on hydroxyapatite surfaces were also examined. Methods Single- and mixed-species biofilms of six common oral bacteria (Streptococcus mutans, Streptococcus gordonii, Actinomyces odontolyticus, Veillonella parvula, Parvimonas micra and Porphyromonas gingivalis) within a flow-cel...
Background Dysbiosis in subgingival microbial communities, resulting from increased inflammatory ... more Background Dysbiosis in subgingival microbial communities, resulting from increased inflammatory transudate from the gingival tissues, is an important factor in initiation and development of periodontitis. Dysbiotic communities are characterized by increased numbers of bacteria that exploit the serum-like transudate for nutrients, giving rise to a proteolytic community phenotype. Here we investigate the contribution of interactions between members of a sub-gingival community to survival and development of virulence in a serum environment - modelling that in the subgingival pocket. Methods Growth and proteolytic activity of three P. gingivalis strains in nutrient-rich broth or a serum environment were assessed using A600 and a fluorescent protease substrate, respectively. Adherence of P. gingivalis strains to serum-coated surfaces was studied with confocal microscopy and 2D-gel electrophoresis of bacterial supernatants used to investigate extracellular proteins. A model multi-species...
mSphere, 2019
Discovered over a half-century ago, lipoteichoic acid (LTA) is an abundant polymer found on the s... more Discovered over a half-century ago, lipoteichoic acid (LTA) is an abundant polymer found on the surface of Gram-positive bacteria. Although LTA is essential for the survival of many Gram-positive species, knowledge of how LTA contributes to bacterial physiology has remained elusive. Recently, LTA-deficient strains have been generated in some Gram-positive species, including the human oral commensal Streptococcus gordonii . The significance of our research is that we utilized an LTA-deficient strain of S. gordonii to address why LTA is physiologically important to Gram-positive bacteria. We demonstrate that in S. gordonii , LTA plays an important role in the presentation of many cell surface-associated proteins, contributing to cell envelope homeostasis, cell-to-cell interactions in biofilms, and adhesion to eukaryotic cells. These data may broadly reflect a physiological role of LTA in Gram-positive bacteria.
European Journal of Dental Education, 2020
The COVID‐19 pandemic has had an immediate and dramatic impact on dental education. The Associati... more The COVID‐19 pandemic has had an immediate and dramatic impact on dental education. The Association of Dental Education in Europe decided to carry out an investigation to assess the immediate response of European Academic Dental Institutions. An online survey was sent to both member and non‐member dental schools to investigate the impact on non‐clinical and clinical education, assessment and the well‐being/pastoral care measures implemented. The preliminary findings and discussion are presented in this paper, for the responses collected between the 25 March and 5 April 2020. The survey at this time of publication is ongoing, and detailed results can be accessed https://adee.org/covid‐19‐european‐dental‐education%E2%80%99s‐immediate‐response.
Bioscience Reports, 2019
There is a strong association between periodontal disease and atherosclerotic cardiovascular diso... more There is a strong association between periodontal disease and atherosclerotic cardiovascular disorders. A key event in the development of atherosclerosis is accumulation of modified lipoproteins within the arterial wall. We hypothesise that patients with periodontitis have an altered lipoprotein profile towards an atherogenic form. Therefore, the present study aims at identifying modifications of plasma lipoproteins in periodontitis. Lipoproteins from ten female patients with periodontitis and gender- and age-matched healthy controls were isolated by density-gradient ultracentrifugation. Proteins were separated by 2D gel-electrophoresis and identified by map-matching or by nano-LC followed by MS. Apolipoprotein (Apo) A-I (ApoA-I) methionine oxidation, Oxyblot, total antioxidant capacity and a multiplex of 71 inflammation-related plasma proteins were assessed. Reduced levels of apoJ, phospholipid transfer protein, apoF, complement C3, paraoxonase 3 and increased levels of α-1-antichy...
European Journal of Dental Education, 2017
It is often the case that good teachers just "intuitively" know how to teach. Whilst that may be ... more It is often the case that good teachers just "intuitively" know how to teach. Whilst that may be true, there is now a greater need to understand the various processes that underpin both the ways in which a curriculum is delivered, and the way in which the students engage with learning; curricula need to be designed to meet the changing needs of our new graduates, providing new, and robust learning opportunities, and be communicated effectively to both staff and students. The aim of this document is to draw together robust and contemporaneous methods of teaching, learning and assessment that help to overcome some of the more traditional barriers within dental undergraduate programmes. The methods have been chosen to map specifically to The Graduating European Dentist, and should be considered in parallel with the benchmarking process that educators and institutions employ locally.
European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, Jan 7, 2018
Post-operative infections are relatively common after posterior spine surgery, and there are seve... more Post-operative infections are relatively common after posterior spine surgery, and there are several observations reflecting different infection complications related to various metals implanted. Here, we selected an array of different bacterial species that are often found in infections associated with orthopaedic implants and tested for inhibition by hydrogen peroxide-treated titanium (Ti-peroxy). To study the possibility of using Ti-peroxy as an antimicrobial prophylaxis, we developed a protocol for standardized susceptibility testing of bacteria. Importantly, we found that the resulting Ti-peroxy was highly antimicrobial against all aerobic species tested, among others, Staphylococcus aureus and Pseudomonas aeruginosa. Proteus mirabilis was slightly more resistant than, for example, Klebsiella pneumoniae and enterococci. In contrast, anaerobic bacteria Cutibacterium acnes and Parvimonas micra were equally susceptible compared to staphylococci. Our findings suggest that the Ti-pe...
BMC Microbiology, 2017
Background: The ecological plaque hypothesis explains caries development as the result of the enr... more Background: The ecological plaque hypothesis explains caries development as the result of the enrichment of acid tolerant bacteria in dental biofilms in response to prolonged periods of low pH. Acid production by an acid tolerant microflora causes demineralisation of tooth enamel and thus, individuals with a greater proportion of acid tolerant bacteria would be expected to be more prone to caries development. Biofilm acid tolerance could therefore be a possible biomarker for caries prediction. However, little is known about the stability of biofilm acid tolerance over time in vivo or the distribution throughout the oral cavity. Therefore the aim of this study was to assess intra-individual differences in biofilm acid-tolerance between different tooth surfaces and inter-individual variation as well as stability of acid tolerance over time. Results: The majority of the adolescents showed low scores for biofilm acid tolerance. In 14 of 20 individuals no differences were seen between the three tooth sites examined. In the remaining six, acid-tolerance at the premolar site differed from one of the other sites. At 51 of 60 tooth sites, acid-tolerance at baseline was unchanged after 1 month. However, acid tolerance values changed over a 1-year period in 50% of the individuals. Conclusions: Biofilm acid tolerance showed short-term stability and low variation between different sites in the same individual suggesting that the acid tolerance could be a promising biological biomarker candidate for caries prediction. Further evaluation is however needed and prospective clinical trials are called for to evaluate the diagnostic accuracy.
The open dentistry journal, 2015
To develop a model in which to investigate the architecture of plaque biofilms formed on enamel s... more To develop a model in which to investigate the architecture of plaque biofilms formed on enamel surfaces in vivo and to compare the effects of anti-microbial agents of relevance for caries on biofilm vitality. Materials and Methodology : Enamel discs mounted on healing abutments in the pre-molar region were worn by three subjects for 7 days. Control discs were removed before subjects rinsed with 0.1% chlorhexidine digluconate (CHX) or 0.2% sodium fluoride (NaF) for 1 minute. Biofilms were stained with Baclight Live/Dead and z-stacks of images created using confocal scanning laser micoscopy. The levels of vital and dead/damaged bacteria in the biofilms, assessed as the proportion of green and red pixels respectively, were analysed using ImageTrak(®) software. Results : The subjects showed individual differences in biofilm architecture. The thickness of the biofilms varied from 28-96µm although cell density was always the greatest in the middle layers. In control biofilms, the overall...
Microbiology (Reading, England), 2009
Surface adhesion plays an essential part in the survival of the commensal organism Streptococcus ... more Surface adhesion plays an essential part in the survival of the commensal organism Streptococcus gordonii in the oral cavity as well as during opportunistic infections such as endocarditis. At least two types of cell surface protein involved in adhesion are found on the surface of Gram-positive bacteria: those anchored via an LPXTG motif by the enzyme sortase A (SrtA) and those associated with the cell surface by, as yet, unknown mechanisms. In srtA(-) mutants, LPXTG-containing proteins have been shown to be released rather than cross-linked to the cell wall. We have therefore used 2D gel electrophoresis of released proteins from an srtA(-) mutant as well as the wild-type strain, followed by peptide identification by MS, to identify a set of novel proteins predicted to be present on the surface of S. gordonii DL1. This includes two large LPXTG-linked proteins (SGO_0707 and SGO_1487), which both contain tandemly repeated sequences similar to those present in known fibrillar adhesins....
BMC Oral Health, 2014
Background: A key element for long-term success of dental implants is integration of the implant ... more Background: A key element for long-term success of dental implants is integration of the implant surface with the surrounding host tissues. Modification of titanium implant surfaces can enhance osteoblast activity but their effects on soft-tissue cells are unclear. Adherence of human keratinocytes and gingival fibroblasts to control commercially pure titanium (CpTi) and two surfaces prepared by anodic oxidation was therefore investigated. Since implant abutments are exposed to a bacteria-rich environment in vivo, the effect of oral bacteria on keratinocyte adhesion was also evaluated. Methods: The surfaces were characterized using scanning electron microscopy (SEM). The number of adhered cells and binding strength, as well as vitality of fibroblasts and keratinocytes were evaluated using confocal scanning laser microscopy after staining with Live/Dead Baclight. To evaluate the effect of bacteria on adherence and vitality, keratinocytes were co-cultured with a four-species streptococcal consortium. Results: SEM analysis showed the two anodically oxidized surfaces to be nano-structured with differing degrees of pore-density. Over 24 hours, both fibroblasts and keratinocytes adhered well to the nano-structured surfaces, although to a somewhat lesser degree than to CpTi (range 42-89% of the levels on CpTi). The strength of keratinocyte adhesion was greater than that of the fibroblasts but no differences in adhesion strength could be observed between the two nano-structured surfaces and the CpTi. The consortium of commensal streptococci markedly reduced keratinocyte adherence on all the surfaces as well as compromising membrane integrity of the adhered cells. Conclusion: Both the vitality and level of adherence of soft-tissue cells to the nano-structured surfaces was similar to that on CpTi. Co-culture with streptococci reduced the number of keratinocytes on all the surfaces to approximately the same level and caused cell damage, suggesting that commensal bacteria could affect adherence of soft-tissue cells to abutment surfaces in vivo.
Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis, 2012
♦Background Peritonitis is the leading cause of morbidity for peritoneal dialysis (PD) patients, ... more ♦Background Peritonitis is the leading cause of morbidity for peritoneal dialysis (PD) patients, and microbial biofilms have previously been identified on catheters from infected patients. However, few studies of catheters from patients without clinical signs of infection have been undertaken. The aim of the present study was to investigate the extent to which bacteria are present on catheters from PD patients with no symptoms of infection. ♦Methods Microbiologic culturing under aerobic and anaerobic conditions and confocal laser scanning microscopy were used to determine the distribution of bacteria on PD catheters from 15 patients without clinical signs of infection and on catheters from 2 infected patients. The 16S rRNA gene sequencing technique was used to identify cultured bacteria. ♦Results Bacteria were detected on 12 of the 15 catheters from patients without signs of infection and on the 2 catheters from infected patients. Single-species and mixed-microbial communities conta...
Microbiology, 2011
The use of dental implants to treat tooth loss has increased rapidly over recent years. 'Smooth' ... more The use of dental implants to treat tooth loss has increased rapidly over recent years. 'Smooth' implants showing high long-term success rates have successively been replaced by implants with rougher surfaces, designed to stimulate rapid osseointegration and promote tissue healing. If exposed in the oral cavity, rougher surfaces may promote bacterial adhesion leading to formation of microbial biofilms which can induce peri-implant inflammation. Streptococcus oralis is an early colonizer of oral surfaces and has been recovered from titanium surfaces in vivo. The purpose of this study was to examine the adherence of clinical strains of S. oralis to titanium with smooth or moderately rough surface topography and to determine the effect of a saliva-or serum-derived coating on this process. Adherence was studied using a flow-cell system with confocal laser scanning microscopy, while putative adhesins were analysed using proteomics of bacterial cell wall proteins. This showed that adherence to moderately rough surfaces was greater than to smooth surfaces. Serum did not promote binding of any of the studied S. oralis strains to titanium, whereas a saliva coating increased adherence in two of three strains tested. The higher level of adherence to the moderately rough surfaces was maintained even in the presence of a saliva coating. The S. oralis strains that bound to saliva expressed an LPXTG-linked protein which was not present in the non-adherent strain. Thus strains of S. oralis differ in their capacity to bind to saliva-coated titanium and we propose that this is due to differential expression of a novel adhesin. Abbreviations: 2DE, 2D electrophoresis; CLSM, confocal laser scanning microscopy; LC-MS/MS, liquid chromatography-tandem mass spectroscopy; S a , average height deviation; S ds , density of summits; S dr , developed interfacial area ratio.
FEMS Immunology & Medical Microbiology, 2010
Pseudomonas aeruginosa and Staphylococcus epidermidis are common opportunistic pathogens associat... more Pseudomonas aeruginosa and Staphylococcus epidermidis are common opportunistic pathogens associated with medical device-related biofilm infections. 16S rRNA-FISH and confocal laser scanning microscopy were used to study these two bacteria in dual-species biofilms. Two of the four S. epidermidis strains used were shown to form biofilms more avidly on polymer surfaces than the other two strains. In dualspecies biofilms, the presence of P. aeruginosa reduced biofilm formation by S. epidermidis, although different clinical isolates differed in their susceptibility to this effect. The most resistant isolate coexisted with P. aeruginosa for up to 18 h and was also resistant to the effects of the culture supernatant from P. aeruginosa biofilms, which caused dispersal from established biofilms of other S. epidermidis strains. Thus, different strains of S. epidermidis differed in their capacity to withstand the action of P. aeruginosa, with some being better equipped than others to coexist in biofilms with P. aeruginosa. Our data suggest that where S. epidermidis and P. aeruginosa are present on abiotic surfaces such as medical devices, S. epidermidis biofilm formation can be inhibited by P. aeruginosa through two mechanisms: disruption by extracellular products, possibly polysaccharides, and, in the later stages, by cell lysis.
BMC Oral Health, 2013
Background Titanium implants in the oral cavity are covered with a saliva-derived pellicle to whi... more Background Titanium implants in the oral cavity are covered with a saliva-derived pellicle to which early colonizing microorganisms such as Streptococcus oralis can bind. The protein profiles of salivary pellicles on titanium have not been well characterized and the proteins of importance for binding are thus unknown. Biofilm bacteria exhibit different phenotypes from their planktonic counterparts and contact with salivary proteins may be one factor contributing to the induction of changes in physiology. We have characterized salivary pellicles from titanium surfaces and investigated how contact with uncoated and saliva-coated titanium surfaces affects metabolic activity in adherent cells of S. oralis. Methods Salivary pellicles on smooth titanium surfaces were desorbed and these, as well as purified human saliva, were subjected to two-dimensional gel electrophoresis and mass spectroscopy. A parallel plate flow-cell model was used to study binding of a fresh isolate of S. oralis to ...
BMC Oral Health, 2013
BackgroundMucosal surfaces are coated with layers of mucus gel that protect the underlying tissue... more BackgroundMucosal surfaces are coated with layers of mucus gel that protect the underlying tissues and promote colonization by members of the commensal microflora.Lactobacillus fermentumis a common inhabitant of the oral cavity, gastrointestinal and reproductive tracts and is one of the most important lactic acid bacteria contributing to the formation of a healthy intestinal microflora. We have investigated the proteolytic activity inL. fermentumin response to interactions with the MUC5B mucin, which is a major component of mucus gels at sites colonized by this micro-organism.MethodsBiofilms ofLactobacillus fermentumwere established in mini-flow cells in the presence or absence of human salivary MUC5B. The proteolytic activity of biofilm cells was examined in a confocal scanning laser microscope with a fluorescent protease substrate. Degradation of MUC5B byL. fermentumwas analysed using SDS-PAGE followed by Western blotting with antisera raised against the MUC5B peptide. Cell surfac...
BMC Oral Health, 2011
Background The soft tissue around dental implants forms a barrier between the oral environment an... more Background The soft tissue around dental implants forms a barrier between the oral environment and the peri-implant bone and a crucial factor for long-term success of therapy is development of a good abutment/soft-tissue seal. Sol-gel derived nanoporous TiO2 coatings have been shown to enhance soft-tissue attachment but their effect on adhesion and biofilm formation by oral bacteria is unknown. Methods We have investigated how the properties of surfaces that may be used on abutments: turned titanium, sol-gel nanoporous TiO2 coated surfaces and anodized Ca2+ modified surfaces, affect biofilm formation by two early colonizers of the oral cavity: Streptococcus sanguinis and Actinomyces naeslundii. The bacteria were detected using 16S rRNA fluorescence in situ hybridization together with confocal laser scanning microscopy. Results Interferometry and atomic force microscopy revealed all the surfaces to be smooth (Sa ≤ 0.22 μm). Incubation with a consortium of S. sanguinis and A. naeslund...
Biochemical and Biophysical Research Communications, 1999
... Enrico Di Stasio a , 1 , Francesca Sciandra a , 1 , Bruno Maras b , Francesca Di Tommaso a , ... more ... Enrico Di Stasio a , 1 , Francesca Sciandra a , 1 , Bruno Maras b , Francesca Di Tommaso a , Tamara C. Petrucci c , Bruno Giardina a and Andrea Brancaccio a , 2. ... 12. SH Gee, RW Blacher, PJ Douville, PR Provost, PD Yurchenco and S. Carbonetto. J. Biol. Chem. ...
European Journal of Public Health, 2020
The prevalence and burden of untreated oral diseases throughout the life course remains high worl... more The prevalence and burden of untreated oral diseases throughout the life course remains high worldwide, and inequalities in oral health and dental care are increasing. This is a major public health issue that is not being enough addressed by the health care systems. To better manage populations' oral health, oral health professionals must be trained to adapt to population needs and societal and technological changes. Furthermore, dental institutions must fulfill their social responsibility by prioritizing educational and research activities that promote advancing individual and community health. In Europe, great variability exists between dental programs within the same country or between countries. This variability is an issue as European graduates can practice around the European Union through mutual recognition of their qualifications. This might lead to inequities in the availability, accessibility, acceptability and quality of health services. The convergence of competencie...