Microbiology - 0420 0425 - Periodontitis and Gingivitis

  1. Dentist measures pocket depth in mm
    • Anything from 1-4 mm is ok
    • Anything 5 mm and greater: start to worry
    • Anything above 7 mm is severe periodontitis
    • With severe attachment loss, you have loss of tooth
  2. Nonspecific plaque hypothesis for periodontitis and gingivitis
    • The cause of the disease is not due to specific bacteria, but abundance of bacteria, the sheer mass of bacteria
    • E.g. lots of bacteria in the blood causes toxic shock
  3. Specific plaque hypothesis
    There are specific bacteria in the plaque that result in disease, analogous to Bacillus anthracis causing a disease
  4. Gingivitis
    • Nonspecific plaque hypothesis
    • plaque -> LPS, protease, etc -> activate cytokine production by white blood cells -> leakage -> mass of white blood cells infiltrating the tissue -> inflammation
  5. Mechanisms of periodontal disease
    • First mechanism:
    • Bacteria -> proteases -> damage and ultimately tissue destruction (directly on the host)
    • Bacteria, particularly G- -> LPS and toxins -> activate macrophage -> engulf the bacteria, and activate epithelial cells via cytokines
    • Epithelial cells -> proteases -> self-destruction
    • Second mechanism:
    • Bacteria -> LPS, toxins -> activate fibroblast -> certain cytokines -> activate osteoclast -> bone resorption
    • Certain periodontal pathogens w/ LPS are very good at activating the pathway leading to bone loss
    • Both mechanisms happen simultaneously
  6. Commonly seen Gram negative anaerobes found in gingivitis and periodontitis
    • Porphyromonas gingivalis (Pg)
    • Treponema denticola
    • Fusobacterium nucleatum
    • Prevotella intermedia
    • Tannerella forsythia
  7. Commonly seen Gram negative facultative anaerobes found in gingivitis and periodontitis
    • Aggregatibacter actinomycetemcomitans (Aa)
    • Eikenella corrodens
  8. Commonly seen Gram positive anaerobes found in gingivitis and periodontitis
    • Peptostreptococcus micro
    • Streptococcus intermedius
  9. Periodontitis is not caused by just one of these bacteria, but by the __________.
    ratio of these organisms
  10. Chronic periodontitis
    • Most common periodontitis
    • Affect older individuals
    • Can affect all the teeth
    • slow process
    • Caused by numerous types of bacteria: Pg, Td (T denticola), Tf
  11. Localized Aggressive periodontitis (LAP)
    • occurs in young adults, adolescents
    • Localized to the central incisors and molars
    • Progresses rapidly; can lose the tooth in a few months
    • Exclusively caused by Aa; the reason why Aa is studied
  12. Checkerboard DNA-DNA analysis
    • developed by Sig Socransky, grandfather of oral microbiology
    • membrane "sandwich"-ed between two devices, plates with slots running across the membrane
    • first add cell lyses from different samples into different slots. The plate is tightly pressed against the membrane, no leakage underneath it.
    • UV crosslink the DNA in the samples onto the membrane in lines.
    • Washoff and rotate the plate w/ slots 90 degrees
    • add bacterial probes from different species individually into the slots; probes are marked
    • DNA-DNA hybridization
    • visualization
    • DNA sample containing specific bacterium will show in the row of the sample and the column of the bacterium
    • Darkness of the color can be calibrated and used to quantify the amount of bacteria contained in the samples.
  13. Pg
    • One of the most well studied periodontal pathogens
    • Unique feature: forms black pigmented colonies, the color is from iron in hemin which is required for growth
    • Anaerobic bacteria
  14. Why is Pg a periodontal pathogen?
    • Pg levels increase during disease progression
    • Pg constitutes a significant percentage of disease microflora, the percentage Pg is greater in disease than in health
    • Pg levels decrease upon return to oral health
    • At lease association, if not causation. (proved in animal models)
  15. Virulent factors of Pg
    • LPS: very potent, stimulates a very strong immune response
    • Capsule: Resists phagocytosis
    • Fimbriae
    • Proteases
    • Hemolysins
  16. gingipains
    • specific Pg proteases: Rgp and Kgp
    • Functions:
    • cleave proteins for energy/carbon source, amino acids
    • Releases heme from hemoglobin
    • for processing proteins, particularly fimbriae, cleave off the signal sequence when secreted
  17. Two animal models for Pg
    • fimA mutant, oral gavage, significantly less bone loss
    • rgpA mutant, subcutaneous implant, 0 abscess, significantly less CFU
  18. LJP=
  19. Aa
    • G(-)
    • strongly associated with LJP/LAP
    • On plates, forms rough, crinkled colonies, with Star-like structure in the center
    • In broth, attaches very strongly to the surface of the tube (sticky, outstanding biofilm former, have to be scraped to get it off)
    • If you dumped the tube, the liquid is clear, the bacteria is attached to the wall of the tube
    • Plays a role in disease in the mouth, a successful pathogen partly because it has this property
  20. Main virulence factors of Aa
    • adherence
    • toxins
  21. Non-specific adherence of Aa
    • Tight adherence operon: tadA-tadG
    • Identified in non-adherent mutation
  22. Other colonization factors of Aa
    • Aae -> epithelial cells
    • ApiA -> epithelial cells
    • These are specific factors that binds to receptors
    • EmaA -> ECM, collagen and other proteins
  23. Aa toxins
    • Leukotoxin -> WBCs
    • Cytolethal distending toxin (Cdt): DNase; lyse host's DNA, inducing apoptosis
  24. Fusobacterium nucleatum
    Sticky bacteria, link between early and late colonizers (glue-like)
  25. early colonizers
    • streptococci sanguis, gordonii, mutans
    • hard for other bacteria to bind except through Fn
  26. late colonizers
    Aa, Pg
  27. Infective endocarditis
    heart valves infected, vegetative growth
  28. Dental procedures can cause
    bacteremia, briefly
Card Set
Microbiology - 0420 0425 - Periodontitis and Gingivitis
Microbiology - 0420, 0425 - Periodontitis and Gingivitis