Periodontal Disease Microbiology PDF

Periodontal Disease Microbiology Module: Oral and Dental Science Tutor: Ms P Lazarou  GDC Learning Outcomes 1.1.3 Explain general and systemic disease and their relevance to oral health 1.1.4 Explain the aetiology and pathogenesis of oral disease 1.1.7 Explain the potential routes of tran...

Periodontal Disease Microbiology Module: Oral and Dental Science Tutor: Ms P Lazarou  GDC Learning Outcomes 1.1.3 Explain general and systemic disease and their relevance to oral health 1.1.4 Explain the aetiology and pathogenesis of oral disease 1.1.7 Explain the potential routes of transmission of infectious agents in dental practice […] Aim: To gain knowledge of the microbial components found in periodontal disease and realise their role. 3  Intended learning outcomes By the end of this session students should be able to: Revise the various mechanisms involved in the aetiology of periodontal disease, namely plaque biofilm, and host immune response and inflammation Recognise the microbial organisms found in periodontal disease and discuss their virulence factors Describe the microbial transition that occurs from gingival health to periodontal disease Discuss the role of bacteria in the aetiology of periodontal disease with reference to historical and current concepts Assessment Forma:ve: Summative Forum discussion Questions in Oral and Dental Sciences Eassessment Pre- session knowledge and related subjects: Microbiology/Bacteria Dental plaque/biofilm Immunology Virulence factors Inflammation 6  Recall Microbiology/Bacteria What is dental plaque/biofilm? How does it form on the tooth surfaces? Immunology- think about the immune response to pathogens Virulence factors- which virulence factors will the oral microorganisms deploy? Mechanisms that microorganism deploy to cause harm Inflammation- what is the process? 7 Oral Bacteria Recap composi:on of dental plaque/ bioFlm 700-1000 species of oral microorganisms 700+ species of oral micro organisms Types of bacteria Some for health and some pathogenic Gram-positive Gram-negative Facultative Anaerobic Image ref: vecteezy.com 8  Primary causative factor - atiological cause of caries and periodontal disease Associated with different types of bacteria and surfaces Can reform within 48 hours Biofilm Revise bio)lm Known to cause disease Bacterial colonies session Community of inter-dependant organisms that grow on a surface Dental plaque = biofilm (note: some subgingival microbes are free-floating in the pocket or only loosely adherent rather than tightly attached) Extra-cellular slime layer: S Protective layer Fluid channels Protects immunities of microbes within - Provides nutrients, oxygen and movement of metabolites and waste Chemical messengers within biofilm Not easy to destruct - they resist destructive by protection provided by slime layer and community 9 Which type is found subgingivally? Gram +ve or Gram Anaerobic –ve? Image ref: columbia.edu 10  Constant balance of how body is coping with bacteria in plaque/biofilm  In health and in stable gingivi:s there is a dynamic equilibrium between dental plaque and the host defences.  The equilibrium is disturbed in periodon::s 11  Balance between bacteria virulence and host response - generally very little damage if even balance If pathogenicity becomes greater can cause tissue damage OR if host response decreases, will also tip to cause tissue damage (destruction of periodontal tissues) This may be due to:  An increased amount of plaque Virulence factors Increase in pathogenicity of the micro-organisms in the biofilm Compromised host defence Immunocompromised patients BUT not always pocketden:stry.com 12 Periodontal Pathogens and their virulence factors Recognised Periodontal Pathogens About 12-15 types of bacteria have been shown to be par:cularly likely to cause periodontal breakdown. These include: Porphyromonas gingivalis (Pg) Tannerella forsythia (Tf) Treponema den:cola (Td) Aggrega:bacter ac:nomycetemcomitans (Aa) 14  Health Thin layers of bacteria More subgingival sites Supra gingival 1-20 cells thick 85% gram positive Subgingival biofilm more in anaerobic Mostly streptococci and actinomyces environment and protected by supra gingival plaque Gingivitis Patients can clean supra gingival Bacteria now subgingival within margin well but sub gingival areas being Slightly false pocketing due to gingivitis swelling missed - less extracellular matrix - 100–300 cells thick Bacteria free floating More than 50% are actinomyces type Now gingivitis stage Increased numbers of anaerobic bacteria more GCF - gingival crevicular fluid subgingival - P.gingivalis Maybe what’s providing nutrients to subgingival pathogens Image ref: columbia.edu 15  What pathogens deploy to be able to colonise and cause harm to host Which Virulence Factors virulence factors will the Proteases - enzymes which are damaging - can digest tissue proteins to gain Not all bacteria do all of these things nutrients and to destroy host defence (antibodies) subgingival Proteinases such as gingipains, pathogens produced by Pg. Can digest tissue proteins for nutrient and to destroy deploy? host defences such as antibodies. Damaging Endotoxins (also called LPS lipopolysaccharide) produced by Gram-negative organisms Haemagglutination of RBC by e.g. Pg can release haem for nutrient and also help the bacteria to adhere Clumping together of red blood cells Image ref: microbeonline.com 16 Fimbraie and Tissue invasion These virulence factors can aid bacterial binding to epithelium, thus aiding tissue invasion. e.g. Pg. Once the bacterium has invaded a host cell it can be safe from host defences and may be more able to replicate. Image ref: Reference.com 17  Capsule protects from being engulfed Fimbrae aids with adhesion to epitheiem Gingipains - protease - enable pathogen to use gingival crevicular fluid as nutrient source and destroy antibodies. Porphyromonas gingivalis Destroy complement factors Destroy host cell inhibitors - destroys collegen and break down of tissues Inflammation - p.g cause even more immune response and inflammatory factors of bone & soft tissues Gram-negative bacillus, anaerobe, non-saccharolytic, Unable to break down sugars and carbohydrates non-motile Unable to move by itself Carbohydrate capsule to resist some host defences Produces gingipains: these enable the bacterium to use GCF (gingival crevicular fluid) as a source of nutrients LPS (Lipopolysaccharide) Helps to break down tissue Haemaglutins & platelet aggregators (? Contributory to heart disease) ?Possibly? Fimbrae and tissue invasion. Can suppress the early PMN (polymorphonuclear leukocytes) response labmedica.com 18  Particular type If causes cell death to immune cells - body will not be able to fight the infection Breaks down protein elements in host cells - such as antibodies Tannerella forsythia Aid in destruction of tissues Gram-negative, anaerobic, fusiform. Very difficult to culture Longer A particular phenotype (prtH) seems to be found much more often in periodontitis than in health Produce proteases and apoptotic- inducing factor (i.e. causes cell death) Science Photo Library 19  Gram negative - motile - can move Spirachete bacteria Treponema denticola Found in periodontal lesions and patients with severe periodontitis Adheres to fibroblasts - collagen fibrosis producing cell - vital for healthy connective tissue and healing - so if t.denticola binds to it the fibroblasts wont be able to do their job. Use GCF components for energy, to aid multiplication Adherence factors can bind to fibroblasts Motile and can invade tissue Disruption of host defences by inducing and degrading cytokines Chemical mediators - if these aren’t present - immune system will be compromised May delay wound healing by inhibiting migration of PMNs They aid in response using phagocytosis- if the bacteria inhibits it, the immune system will be delayed. T.denticola produced enzymes - use lysis to destroy antibodies and other chemical mediators such as complement factors Science Photo Library 20 Aggregatibacter actinomycetemcomitans Associated with aggressive periodontitis form (? Grade C: rapid rate of progression), also with periodontitis that has been refractory to treatment NOT motile or anaerobic! Gram-negative Coccoid baccillus (short rod) Virulence factors include Leukotoxin (can kill WBC, so disrupts the host defences) Other toxins can destroy fibroblasts and epithelial cells. Also produces proteases, including collagenase schaechter.asmblog.org Can invade host epithelial cells 21 Role of bacteria in Periodontal Disease  Some historical and some contempory Theories on the role of bacteria in Periodontal Disease 5 Hypotheses: 33 1) Non-specific Plaque Hypothesis HISTORICAL 2) Specific Plaque Hypothesis 3) Ecological Plaque Hypothesis 4) Microbial Homeostasis- Host Response Hypothesis 5) Keystone Pathogen- Host Response Hypothesis CONTEMPORY Image refIcon4nder 23  Obvious…. Years and years thought it was thought a huge amounts of plaque will sit in gingival sulcus and lead to inflammation in adjacent gingival sulcus and lead to destruction Non Specific Plaque Hypothesis Stagnation of plaque biofilm Large numbers of bacteria Within gingival sulcus Gingival inflammation Periodontal disease Tissue destruction 24 Issues with the Non Specific Plaque Hypothesis You can get patients with huge amounts of plaque and does not progress to periodontal disease from gingivitis. Can also have very light plaque in mouth but big destruction loss.  Too simplistic  Most cases of gingivitis never progress to periodontitis ?  Some patients with light biofilm deposits suffer from periodontitis Some sites in the patient’s mouth will suffer periodontal destruction whereas other sites may not be affected 25  This hypothesis proposes its the microbial composition rather than amount that determines development of disease. Specific Plaque/Microbial Shift Hypothesis As periodontal disease develops: ↓ SHIFTING of oral microbiota General bacteria build up - commensal bacteria, live in harmony From: beneficial microbes… Gram-positive ↓ To: Specific Pathogens... Gram-negative Mainly anaerobic 26 Socransky’s Microbial Complexes Which oral bacteria are associated with 1998 - different periodontal conditions/diseases are caused by specific bacteria periodontal disease? Studies identified various periodontal diseases/conditions caused by specific bacteria: Tannerella forsythia, Porphyromonas gingivalis, Treponema denticola. Interdependent with each other.Depend on each other to survive Grouped together on pathogenicy - how much disease they can cause. Socransky grouped microbes into colour-coded ‘complexes’ Orange/red: major causative agents of periodontal disease Yellow/green/blue/purple: compatible with gingival health 27  Socransky’s Microbial Complexes Periodontal pathogens Gram negative Gram positive 28  Issues with the Specific Plaque Hypothesis This hypothesis becomes more less certain in more recent research ?  It has since been found that the red complex micro organisms (P. gingivalis and T. Forsythia) exist in stable/healthy periodontal sites.  Do these pathogens directly cause destruction of periodontium?  More recent research shows more varied and diverse oral microbes (700+). Newly recognised bacteria found possibly to be more causative than the red complex species; concept of specific types causing periodontal destruction less certain. Current research demonstrates Gram-positive bacteria found in larger amounts in periodontal pockets 29  Virulence factors of bacteria use gingival crevicular fluid as nutrients - helps them to provide and provide nutrients for pathogens. Contemporary theories on the role of bacteria: Ecological Plaque Hypothesis Changes in subgingival environment: nonspecific bacteria triggers host inflammatory response The altered environment favours increase of pathogenic bacteria in biofilm: higher GCF flow, increased bleeding, raised pH, decrease oxygen concentration Mostly anaerobes - all environmental changes favour the pathogenic bacteria Damage to the periodontal tissues Shift in local environment is the trigger that drives changes in microbial types - may result in periodontal destruction 30 Support for this Hypothesis: Deeper pocket sites and bleeding on probing sites – found to have increased gingival crevicular fluid (GCF).  GCF changes microbial ecology- enables growth of pathogenic bacteria  Changes in environmental factors (GCF/pH/temperature/oxygen decrease) are forces driving dysbiosis in gingival sulcus disruption of microbial environment Subgingival debridement changes the ecosystem- reduces number of pathogens. Gingival inflammation reduction = decrease of GCF, halting nutrient source of bacterial growth. 31 Microbial Homeostasis- Host Response Hypothesis Pathogenic biofilm community Triggers uncontrolled host response: immune response Damage to periodontal tissues Proposes - pathogenic biofilm community will trigger host response - uncontrolled host response - strong response - causing damage to periodontal tissues by destruction of tissues. 32 Microbial Homeostasis- Host Response Hypothesis cont… Genetic variations, inflammatory immune response and environmental factors - all major factors that influence the start and progression of periodontal disease.  Now recognised that host-related traits, e.g. genetic variations, and inflammatory immune response, environmental factors e.g. smoking, stress, systemic diseases- all major factors which influence the initiation and progression of periodontal disease  Page and Schroeder (1976) stated that gingivitis does not progress to periodontitis unless some other unknown factor tips the delicate biofilm- host balance toward further tissue destruction  Shift from beneficial microbes to pathogenic ones triggers a strong host inflammatory response which enables periodontal tissue destruction 33 Support for this Hypothesis: Biofilm microbiota linked to periodontal health remains stable in a state of biological equilibrium or homeostasis Research has not proven that bacterial pathogens are directly responsible for periodontal destruction Robust evidence shows that it is the uncontrolled host inflammatory and immune response that cause the tissue destruction 34 Keystone Pathogen-Host Response Hypothesis Theory - specific bacterial species is key in the shift from symbiotic (harmless) microbes TO the disbiotic (pathogenic) microbes in biofilm communities. Triggers uncontrolled host response - causes periodontal destruction. Keystone species in biofilm Keystone species - species that has a disproportionately large effect on community relative to number - can be small numbers of pathogens but will have disproportionate effect and will trigger host response. Intensive affect of microbes (P.gingivalis) Trigger SHIFT to dysbiotic biofilm community Uncontrolled host response initiated Damage to periodontal tissue 35 Support for this Hypothesis: Previous research could not provide solid evidence to show that specific bacteria are the direct cause of periodontal destruction. Current evidence demonstrates that the immune response and uncontrolled host inflammatory response cause the tissue destruction found in periodontal disease. 36 What are the causes of periodontal disease? Aetiology of Periodontal Disease Aetiology of Periodontal Disease Multifactorial: Microbial factors Environmental Factors: e.g smoking, poor OH, pre-existing pockets , plaque-retentive factors/secondary local factors Host defence factors: e.g PMN defects certain inherited geno-types revodonto.bvsalud.org 38 References and further reading Gehrig, J. Shin, D. Willman, D. (2018) Founda'ons of Periodon'cs for the Dental Hygienist, 5th ed; 253-258. Popove, C. Dosseva-Panova, V. Panov, V. (2013) Microbiology of Periodontal Diseases. A Review, Biotechnology & Biotechnological Equipment, 27:3, 3754-3759, DOI: 10.5504/BBEQ.2013.0027 Mendes, L. Azevedo, N. F. Pinto, M. G. (2015) Rela7onship between invasion of the periodon(um by periodontal pathogens and periodontal disease: a systema7c review, Virulence, 6 (3), 208-215. DOI: hcps://doi.org/10.4161/21505594.2014.984566 Dietrich, T., Ower, P., Tank, M. , West, N., Walter, C., Needleman, I., Hughes, F., Wadia, R., Millward, M., Hodge, P. J., Chapple, I., & on behalf of the Bri:sh Society of Periodontology (2019). Periodontal diagnosis in the context of the 2017 classiFca:on system of periodontal diseases and condi:ons – implementa:on in clinical prac:ce. Bri:sh Dental Journal, 226(1), 16- 22. hcps://doi.org/10.1038/sj.bdj.2019.3 39