Interaction between microorganisms and host Flashcards
Describe the characteristics and classification of bacteria
• Gram positive vs gram negative; they had different structures, components and functions of the cell wall
- Aerobic bacteria require oxygen for growth
- Anaerobic bacteria thrive in environments with limited amounts of oxygen or no oxygen present
- Facultative bacteria are those that can grow with or without oxygen
• Commensal bacteria have a relationship in which they gain food and other benefits from one another without cause harm or helping either
Shapes:
• Coccus (plural cocci): spherical in shape
• Bacillus: describes gram-positive, rod-shaped cells; usually aerobic or facultative anaerobes
• Spirillum: describes spiral-shaped cells
Describe the mircobial ecology of a healthy periodontium
- Primarily gram positive facultative species
- Members of Streptococcus and Actinomeyes
- Small proportions of gram-negative species
- P. Intermedia, F. Nucleatum, Capnocytophaga, Neisseria and Veillonella species
• Few spirochetes and motile rods
- Some bacterial species are protective or beneficial to the host by preventing colonization or proliferation of pathogenic microorganism
- E.g. S. Sanguis, Veillonella parvula, and C. Ochtraceus
Describe the mircobial ecology of a diseased periodontium
- Gram negatives
- Rods, spirochetes
- Motile
- Obligate anaerobes
- Proteolytic
• A vicosus: a gram-positive rod shaped facultative anaerobe
Actinomyces naeslundii have been implicated in periodontal disease and root caries
Describe the S. sanguis and Actinomyces naeslundii bacteria in health
S. Sanguis is gram positive and is found in plaque of healthy mouth. It makes oral cavity less hospitable for other strains of streptococus that cause caries.
Also, Actinomyces naeslundii, a gram positive rod shaped bacteria that is generally associated with good oral health. Occurs in high numbers in dental plaque, cemental caries, and tonsillar crypts
Describe the A vicosus and Actinomyces naeslundii bacteria in disease
A vicosus a gram-positive rod shaped facultative anaerobe which occurs in high numbers in dental plaque, cemental caries, and tonsillar crypts. It is an opportunistic pathogen.
Actinomyces naeslundii have been implicated in periodontal disease and root caries
Describe the microbial shift that occurs as the periodontium moves from a healthy to a diseased state
- Gram positive –> Gram negative
- Cocci –> rods –> spirochetes
- Nonmotile –> motile
- Facultative anaerobes –> obligate anaerobes
- Fermenting –> proteolytic
Name the oral microorganisms associated with periodontal disease
Aggregatibacter actinomycetemcomitans
Tannerella forsythia
Porphyromonas gingivalis
Describe the aggregatibacter actinomycetemcomitans bacteria
- Gram negative
- Facultative anaerobe
- Non- motile
- Strongly associated with aggressive forms periodontitis
- Capable of evading normal host immune response
- Can destroy gingival connective tissue and bone
Describe the tannerella forsythia bacteria
- Gram negative
- Anaerobic
- Pleomorphic rods
- Significant risk factor indicator with those who have periodontitis. Detected in epithelial cells of periodontal pockets
Describe the porphyromonas gingivalis bacteria
- Gram negative
- Anaerobic
- Nonmotile
- Rod- shaped
- Seen in disease that are worsening e.g. pockets/ bone loss
- Inhibits migration of immune cells
Outline the components the immune system
Innate Immunity-Natural Immunity
• First line of defense against disease
• Includes external barriers e.g. skin, mucous membranes
Adaptive-Memory
• Develops throughout life
Passive Immunity (borrowed from another source)
• Short duration
• E.g. Mother’s breast milk provides temporary protection against disease
Outline the function of the immune system in response to periodontitis
- Secretory IgA and numerous enzymes and antimicrobial factors present in the saliva neutralize microbial components on mucous membranes
- All these factors attempt to minimize the effect of the offending biofilm complex and may function synergistically
- In the presence of periodontitis and increasing severity of periodontitis, there is first an elevation in the cell-mediated both CD4+ (T-helper cells) and CD8+ (suppressor or “killer” cells) and second, periodontitis specific antibody formation
- However, the intensity of the immune response varies greatly between individuals
Describe the histo-pathological changes to the structures of the periodontium in gingivitis and periodontitis.
Initial lesion:
• Collagen is lost around blood vessels
• Connective tissue is destroyed by cytokines (IL-1, IL-6, IL-8, TNFα)
Early lesion: • Rete pegs begin to develop in junctional epithelium (JE) • More destruction of collagen at JE • Fibre groups begin to be destroyed • Production of new collagen decreases
Established lesion:
• Deepened sulcus
• Abnormal oxygen in blood flow within gingiva makes colour bluish
Advanced lesion:
• Destruction of connective tissue and periodontal ligament fibers, connective tissue and bone
• Atrophy of epithelium
• Oedema
Apply the knowledge of the process of inflammation to the oral cavity with particular reference to periodontal disease
- Tissue destruction phase – (plaque biofilm extends apically and laterally on root surface)
- High levels of cytokines produced: MMPs and PGE
- Destruction of connective tissue and periodontal ligament fibers, connective tissue and bone
- Chronic immune response (protecting host against systemic infection)
- Lesion extends into alveolar bone
- Apical extension of pocket
Briefly outline the factors that lead to periodontal destruction including the host response
- Pathogenic bacteria infect the periodontium
- Body responds by mobilizing defensive cells, which release series of chemicals to fight bacteria
- However, body’s immune system causes tissue destruction in an attempt to stop bacterial infection
- Complex interactions between periodontal pathogens and host response determine the onset and severity of periodontal disease
- Bone loss mechanism: plaque products induce progenitor cells to differentiate into osteoclasts OR macrophage releases TNFa which stimulates fibroblast to secrete PGE2, which stimulates osteoclasts
