Microbiology - 0420 0425 - Periodontitis and Gingivitis

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  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=
    LAP
  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

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Author:
akhan
ID:
319359
Filename:
Microbiology - 0420 0425 - Periodontitis and Gingivitis
Updated:
2016-05-13 19:55:43
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microbiology
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Description:
Microbiology - 0420, 0425 - Periodontitis and Gingivitis
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