Pathogenesis: Adhesion, Invasion and Virulence Factors · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The obstacle course of infection

Science · Microbiology · ages 20-22
Name ______________________   Date ____________

  1. One germ grips the lung lining and its cousin grips the gut. Which diseases result?

    • The same disease from both, since sticking changes nothing
    • Breathing illness from the lung gripper and diarrhoea from the gut gripper
    • Diarrhoea from both, since the two germs are cousins

  2. Which order do the four gates of infection run in?

    • Reach a surface, stick, push past defences, secure iron
    • Secure iron, stick, reach, push past defences
    • Reach a surface, secure iron, stick, push past defences

  3. Which toolkit item steals iron for the germ?

    • Enzymes that dissolve tissue barriers
    • Capsules that shield germs from phagocytes
    • Siderophores that steal iron from the host

  4. A mutant grows normally in a dish yet causes far weaker disease. What does that gap tell you?

    • The deleted gene is a true virulence factor
    • The deleted gene only controls growth speed
    • The test failed, since growth and disease always match

  5. A pathogen loses its adhesion gene but still grows in a dish. What happens at its usual site?

    • It infects as usual, since growth in a dish is normal
    • It fails to grip and infect its usual site
    • It switches to a new tissue entirely on its own

  6. You want the cheapest place to stop an infection. Where do you block it?

    • At the toxins, after the germ has settled in
    • At feeding, by adding extra iron for the germ
    • At sticking, since every later gate needs the grip

  7. A gene that slows growth in a dish but leaves disease unchanged marks a true virulence factor.

    Circle one:   True   False

  8. A new strain tests positive for gripping lung tissue. A friend claims it will cause diarrhoea. What is wrong with that claim?

    • Nothing is wrong; tissue grip cannot predict disease
    • New strains never follow the sticking rule
    • Lung grippers cause breathing illness, so diarrhoea needs gut grippers
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Answer key

For grown-ups. Fold this page away before handing over the rest.

The obstacle course of infection W1-mt_8SPj_E5foc-s1

  1. Breathing illness from the lung gripper and diarrhoea from the gut gripper · Adhesins pick the tissue, so lung grippers sicken lungs and gut grippers sicken the gut.
  2. Reach a surface, stick, push past defences, secure iron · The gates run in fixed order: reach, stick, enter, feed. Later gates depend on the earlier ones.
  3. Siderophores that steal iron from the host · Siderophores are the iron thieves of the toolkit. Capsules and enzymes do different jobs.
  4. The deleted gene is a true virulence factor · Normal growth with weaker disease is the signature of a true virulence factor. The gene served harming, not growing.
  5. It fails to grip and infect its usual site · Without the grip, the germ cannot hold its usual site. Growth in a dish never proves it can infect.
  6. At sticking, since every later gate needs the grip · Blocking the grip starves every later gate at once. Later blocks leave earlier gates intact.
  7. False · A true factor shows the reverse pattern: normal growth with weaker disease. Slow growth alone is not virulence.
  8. Lung grippers cause breathing illness, so diarrhoea needs gut grippers · The grip predicts the tissue, and the tissue predicts the disease. Lung grip means breathing illness.
Worksheet · LightMySky