Microbiology of Periodontitis

• What are pathogens/ periodontopathogens?

  An infection agent that causes disease in its host

  
• How many species of pathogen are in the oral cavity & periodontal pocket?

  700 species - oral cavity

  
  

  400 - periodontal pocket
• What are examples of Periodontopathogens

  Aggregatibacter actinomycetemcomitans

  Porphyromonas gingivalis

  Prevotella intermedia

  Tannerella forsythensis

  Campylobacter rectus

  Fusobacterium nucleatum

  Treponema denticola

  Spirochaetes
• What is the difference in morphology between Cocci, Bacilli and other pathogens?

  
• What contributes to a micro - organisms motility?

  Structural elements

  Flagella, Fimbria, Filaments

  (Glide, spiral, tumble)

  
• What is the difference in Gram Negative and Gram Positive micro organisms in their surface structure?

  Gram Negative

  • Stain- Pink
  • Thin single Peptidoglycan layer
  • High Lipopolysaccharide content
  • High Lipid and Protein content
  • High Resistance to Physical disruption
  • More Resistance to antibiotics

  Gram Positive

  • Stain- Purple
  • Thick mulitlayers Peptidoglycan layer
  • Minimal Lipopolysaccharide content
  • Low Lipid and Protein content
  • Low Resistance to Physical disruption
  • More susceptible to Resistance to antibiotics

  
• What makes a micro-organism a pathogen?

  Its Virulence

  Characteristics of an organism that allow it to invade a host, cause disease and evade host defences.
• What are some Virulence Factors?

  • LPS - endotoxin
  • Leucotoxin
  • Cytotoxins
  • Chemotaxis
  • Collegenases
  • Immunosuppressive factors
  • Fc Binding protein
  • Invasins
  • Bacteriocins
  • Adhesins
  • Tissue invasion
  • Strains/clones

  
• What is the difference between health and disease in terms of microbial composition?

  Health: gram +ve, aerobic, non-motiles predominate

  Disease: 75% gram -ve, 90% obligatory anaerobic, motiles/spirochaetes predominate

  
• What are the mechanisms of pathogenicity?

  1. Colonisation by the pathogen

  
  

  2. Production of factors by the pathogen that damage the host

  1. Directly

  2.Indirectly

  
  

  Allowing pathogen to spread
• What are the dependent factors for the colonisation of the pathogen?

  Growth requirements

  Ability to attach to surfaces

  Co-aggregation

  Nutrient supply

  Competition with other organisms

  Evasion of host defences
• What are the growth requirements for colonisation?

  • aerobe/anerobe
  • subgingival
  • temp 35 degrees
  • alkalinity 7-8 pH

  
• How do bacteria attach to surfaces?

  • adhesins (surface structure macromolecules)
  • Fimbriae (Filamentous proteins on surface of bacterial cells that behave as adhesins for specific adherence)

  
• What is Co- aggregation?

  Process by which genetically distinct bacteria attach to one another via specific molecules

   Influences the development of colonies of commensal and complex organisms resulting information ofmulti-species biofilms
• How do co-aggregated groups join?

  Bridging organisms
• What is Fusobacterium Nucleatum?

  • Bridging Organism
  • Adheres to Gram-positive and Gram-negative microorganisms
  • Mediates co-aggregation
  • anaerobes rely or aerobes vice versa

  
• What are food webs?

  The metabolic products of one species may be an essential nutrient for another!
• What is an example of a food web?

  • Campylobacter rectus produces protohaem (red organic pigment containing iron to which O2 binds, found in haemoglobin/myoglobin)to Stimulate growth of Bacteroides species: Prevotela melaninogenica and Porphyromonas Gingivalis
  • Prevotela melaninogenica produces formate, Stimulates growth of Campylobacter rectus
• What is the Crevicular Fluid and what does it contain?

  Fluid that fills the gingival sulcus.

  -Primary source of nutrients

  - Provides proteins, glycoproteins and lipoproteins

  - Proteolytic bacteria breakdown proteins into their component parts which are themselves nutrients

  
• What happens to the pH of the crevicular fluid where the gingival index increases?

  The pH increases (alkaline)

  This is due to bacterial production of ammonia and elevated supply of urea during inflammation

  The growth and enzyme activity of Porphyromonas Gingivalis is favoured by alkaline conditions
• What are some examples of nutritional interactions?

  • haemin - crevicular fluid - black pigment, bacteroides
  • hormones - crevicular fluid - bacteriodes intermedius
  • formate - P, melaninogenica - campylobacter
  • lactate - crevice bacteria - spirochaetes
  • protohaeme - campylobacter - porphyromonas

  
• The environment favours certain organisms, what are some environmental factors?

  - Temperature

  - Alkalinity

  - Oxygen (aerobic/anaerobic)
• What are some interactions between bacteria and the toxins they produce?

  • Proteinaceous toxins produced by bacteria are lethal for other strains and species of bacteria
  • Increase cell permeability of target bacteria with leakage of essential cell components (molecues,DNA,RNA)
  • Aa produces Actinobacillin, toxic to S Sanguis and A Viscosus (plaque formers)
  • Some streptococci produce hydrogen peroxide that kills Aa
• What is 'AA'?

  • Aggregatibacter Actinomycetemcomitans
  • 'TOOTH KILLER'
  • rod-shaped
  • several virulent factors
  • Present in small amounts in healthy mouth
  • If given the opportunity to grow, high risk of perio
  • ability to invade and destroy perio tissue/suppress immune system.
• How do pathogens evade the host defence systems?

   Capsules and slime layers

   Leukocyte killing properties e.g. Aa

   Degradation of immunoglobulins e.g. Capnocytophaga

   Degradation of fibrin that would otherwise trap bacteria

   Dysregulation of cytokine networks e.g. Porphyromonas Gingivalis
• Direct tissue damage is caused by...

  Enzymes that breakdown periodontal tissues

  Examples:

   Protease (breaks down protein)

   Collagenase (breaks down collagen)

   Hyaluronidase (breaks down hyaluronan [polysaccharide] in extracellular matrix)

   Chondroitin sulphatase (breaks down chondroitin sulphate –component of proteoglycans involved in structural and regulatory roles in the body)
• what can increase mucosal permeability?

  • Metabolic products (bi - products of organisms physical and chemical processes)
  • volatile sulphur compounds
  • volatile fatty acids
  • amines
  • ammonia
  • indole
• What are examples of Tissue/cell invaders?

   Aa(Aggregatibacter Actinomycetemcomitans)

   Pg(Porphyromonas Gingivalis)

   Pi(Prevotella Intermedia)

   Fn(Fusobacterium Nucleatum)
• What is a Lipopolysaccharide (Endotoxin)?

  • Large complex molecule of polysaccharides linked to lipid
  • gram -ve bacterial cell walls causing bone resorption and complement activation.impermeable barrier for the bacteria

   Provides surface adhesion for the bacteria

   Is directly cytotoxic – binds to CD14 receptors on macrophages, granulocytes, lymphocytes and triggers cell response

   Trigger strong immune response
• What is Lipoteichoic acid?

  Lipid linked teichoic acid. Only in Gram + bacteria

  - From gram positivecell walls stimulates bone resorption
• What happens in a call mediated (innate) response?

  • activated macrophages
  • activated T cells
  • cytokines released: IL-1 bone resorption pro-inflammatory, IL-60 antibody production osteoclast differentiation B cell differentiation, IL-8 attraction of PMN’s (produce matrix metalloproteinases, bystander damage),
  • TNFα 2Bone resorption, Pro-inflammatory
• What is Pg (Porphyromonas Gingivalis)?

  Nonmotile, Gram-negative, rod-shaped, anaerobic, pathogenic bacterium

  Collagen degradation observed in chronic periodontal disease results in part from the collagenase enzymes of this species.

  It has been shown in anin vitrostudy thatP. gingivaliscan invade human gingival fibroblasts and can survive in the presence of antibiotics.

  P. gingivalisinvades gingival epithelial cells in high numbers
• What happens in Indirect tissue damage in the Humoral (adaptive) response?

  • Antibody Production
  • Complement activation
  • Inflammatory cells attracted
  • Release of tissue destructive enzymes
• How do we determine an active site?

  - Probing

  - BOP
• How can we monitor disease activity?

  - BOP

  - Suppuration (not reliable indicator of disease)

  - Continued absence of BOP of treated sites (predictor of maintenance of perio health)

  - Biomarkers
• What 3 species of bacteria are consistently prevalent in periodontal disease associated with plaque?

  Aggregatibacter Actinomycetamcomitans (Aa)

  
  

  Porphyromonas Gingivalis (Pg)

  
  

  Tannerella Forsythus (Tf)

  (formerly Bacteroides Forsythus)

  
  

  And often Treponema Denticola
• Socransky et all 1998

  
  

  5 complexes of bacteria assigned to colours

  
  

  Shows relationship between co existing bacteria

  
• What are Dark Purple, Yellow & Green complexes?

  • sites rarely associated with active disease
  • Dark Purple: A, Viscosus
  • Yellow: strep. mitis, strep. oralis, strep. intermedius, strep. sanguis, e. corrodens
  • Green: E. corrodens, c. gingivalis, c. sputigena, c. ochracea

  
• What are Purple Complexes?

  sites that respond well to therapy

  v. pervula, a. odontolyticus

  
• What are Orange Complexes?

  present in most active sites, with attachment loss and deepest pockets, closely linked with each other and red complex species

  Prevotella intermedia, prevotella nigrescenes, peptostreptococcus micros, fusobacterium nucleatum, camlylobacter rectus, selemonas constellatus