Microbiology of chronic perio and flora of active sites

• How many species are found in the oral cavity ?

  700
• How many species are found in the periodontal pocket

  400
• What is a periodontopathogen 


  An infections agent that causes perio disease in its host
• Periodontopathogens

  Aggregatibacter actinomycetemcomitansPorphyromonas gingivalisPrevotella intermediaTannerella forsythensisCampylobacter rectusFusobacterium nucleatumTreponema denticolaSpirochaetes
• Mos can be classified by?

  morphology

  Aggregation
• What else should be considered about MOS?

  • structure of their environment ie. plaque film or tissue penetration
  • Physical connections and coaggreation with other organisms possible?
• Motility?

  structural elements which can provide mobility

  For example:

  • flagella
  • Fimbria
  • Filaments

  Movement:

  • glide
  • Spiral
  • tumble
• Gram negative bacteria

  Stain = pink

  Peptidoglycan layer = thin (one layer)

  LPS content = high

  Lipid and protein content = high due to outer membrane

  Resistance to disruption = high

  Resistance to antibiotics = more resistant
• Gram Positive Bacteria

  Stain = purple

  Peptidoglycan layer = thick

  LPS content = none

  Lipid and protein content = low

  Resistance to disruption = low

  Resistance to antibiotics = more susceptible
• What makes a MO a pathogen

  Virulence
• What is virulence

  characteristics of an organism that allow it to :

  • invade a host
  • cause disease
  • evade host defences
• Virulence factors

  • LPS / endotoxin
  • Leucotoxin
  • Cytotoxins
  • Chemotaxis inhibitors - PMNS
  • Collagenases
  • Immunosuppressive factors - inhibit IgG and IgM
  • FC binding
  • Invasins
  • Bacteriocins
  • Adhesins
  • tissue invasion
  • Stains and clones
• What do leucotoxins do

  inhibit PMNS Igs and complement activation
• what do cytotoxins do?

  inhibit fibroblast proliferation
• Immunosupressive factors

  inhibit IgG and IgM
• Fc binding protein

  inhibit production of IgG and IgM
• Invasins

  penetrate and inactivate phagocytes
• what do bacteriocins do?

  kill bacterial organs and changes healthy balance
• what are adhesins ?

  attachment pili and fimbriae
• Which pathogens invade tissue?

  • Aa invades epithelium and connective tissue
  • Pg invades and persists in epithelium
• Name one strain / clone

  JP2 clone Aa
• Microbial composition in health ?

  • gram positive
  • aerobic
  • Non motile
• Microbial composition in disease ?

  • 5% Gram –ve
  • Motiles/spirochaetes predominate
  • 90% obligatory anaerobic
• Mechanisms of pathogenicity?

  1. colonisation by pathogen
  2. Production of factors by the pathogen that damage the host indirectly or directly which allows pathogen to spread
• what are the dependent factors of colonisation of the pathogen?

  • Growth requirements
  • Dependent factors
  • Evasion of host defences
  • Competition with other organisms
  • Nutrient supply
  • Co-aggregation
  • Ability to attach to surfaces
• Growth requirements for colonisation?

  • subgingival temperature = is increased in diseased sites (normally 35)
  • Alkalinity = normal is 6.7, pocket it 7-8.5 which encourages plaque growth and expression of pathogens
  • O2 levels = obligate anaerobes or obligate?
• Normal health pH is

  6.7
• In a pocket pH is?

  7-8.5
• Adhesins are

  surface structure macromolecules
• Attaching to surfaces via fimbriae

  Filamentous proteins on the surface of bacterial cells that behave as adhesins for specific adherence
• Coaggregation

  a process by which genetically distinct bacteria attach to one another via specific molecules

  Can influence the dev of colonies of commensal and complex organisms which results in formation of multi species biofilms
• Joining co aggregated groups requires what?

  bridging organisms
• What is an example of a bridging organism?

  fusobacterium nucleatum

  commensals pathogens

  + ------>. +

  early colonisers late colonisers
• Fusobacterium nucleatum ?

  • adheres to wider range of gram positive and negative
  • Mediates coaggregations between O2 tolerant and anaerobic bacteria
  • Important as anaerobes need O2 using bacteria to maintain favourable growth environment
• Nutrient supply

  Food webs - The metabolic products of one species may be anessential nutrient for another.
• Food web examples?

  campylobacter rectus produces protohaem

  Stimualtes growth of bacteroides species : prevotela melaninogenica and porphyromonas gingivalis

  
  

  Prevotela melaninogenica produces formate and stimulates growth of campylobacter rectus
• crevicular fluid ?

  • is a primary source of nutrients
  • Provides proteins, glycoproteins and lipoproteins
  • Proteolytic bacteria breakdown proteins into their component parts which are nutrients in themselves

  Eg:

  • amino acids
  • Heme from hemoproteins
  • Essential peptides
• Crevicular fluid and pH

  pH increases (becomes more alkaline) where gingival index increases due to bacterial production of ammonia and elevated supply of urea during inflammation. the growth and enzyme activity of PG favoured by alkaline conditions
• Competition - bacteriocin production ?

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

  Proteinaceous toxins produced by bacteria that are lethal forother strains and species of bacteria