Module 4 summary

• pathogenicity vs virulence 


  pathogenicity: ability of pathogens to affect the host

  virulence: measure of pathogenicity
• forms of disease transmission

  1. direct host to host: transmission of disease from host to host without assis
  2. indirect host to host: transmission of disease from host to host with assist
• when does an infection = disease

  when a micro-organism that is established in a host = damages to the host
• capsule related to pathogencity

  encapsulated bacteria resist pathogcyts to grow
• when can bacteria indigenous to the mouth become a problem

  when they colonise surfaces, grow and persist and damage metabolites
• why is a fever univsresist endotoxin repsonse

  it stimulates host cell to release cytokines which affected the temp control centre in the brain
• list different exotoxins

  1. cytoylitic: cell lysis: degrades cyto membrane
  2. AB toxins: binds to receptors. a moves to b subunit
  3. superantigen: stimulates large number of immune cell = inflammation and tissue damage
• how lactic acid = dental carriers

  • lactic acid dissolves calcium phosphate
  • proteolysis occurs through action of bacterial proeolotic enzymes
• epidemic vs endemic 


  epidemic: increase number of cases in localised pop

  endemic: constant pop and low levels over a long time
• food infection vs intoxication

  food infection: ingested of pathogen contaminated food

  food intoxication: illness by ingestion
• key feature of bacillus to make it impossible to get rid of

  endospore
• difference between sterpotkinase and coagulate

  strep: used as a fibrinlytic enzyme to dissolve fibrinclots = invassion impossible

  coagulase: forms and insoluble fibrin layer = protection
• how common source and host to host differ

  common source: single conatmination source, involves large number of people suddenly beocming ill in a short period of time

  host to host: person to person contact, more gradual increase and decrease un number of indivs
• most heavily conolonised organ by bacteria is

  large instestine
• human oral microbiota consists of

  diverse aerobic and anaerobic microorganisms
• an inanimate object that transmits infectious agents between host is called

  fomite
• strep throat

  pyogenes
• exotoxins 


  toxic proteins released from pathogen when it grows
• endotoxins are 


  part of gram -ve cell envelope
• tetanus develops from a puncture wound because

  endo spores geminate in anoxic conditions
• Normal microbiota helps to … colonisation of pathogenic organisms

  • prevent
• endemic level is the level of disease that is present in a population (flat)
• differences between endotoxins and exotoxins

  endo: lipid A portion of outer membrane of gram -ve released on cell lysis that induces an intense immune response, it is gram -ve only!, heat stable, and not toxic

  exotoxins: gram -ve and +ve, decrease by heat and chemicals, highly toxics, no fever and has proteins
• mode of action for AB toxins

  • binds to host cell surface receptors and damage the cell when the A subunit is transferred across the targeted cytoplasmic membrane by the B subunit
• most dominant bacteria in intestine

  1. firmicutes
  2. bacteroidetes
• common sources

  1. food - salmonellosis
  2. water - cholera