Food safety & hygieneLesson 2 of 2 in the course Foodborne illness

Listeria: Bacterial Biology, Infection, and Food-Safety Prevention

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces the genus Listeria, its main bacterial characteristics, and where it is found. Understanding these features helps explain why the organism can persist in food environments and why correct identification matters.

Listeria is a genus of bacteria that can live inside mammalian cells. As of 2024, 28 species have been identified. Members of the genus are Gram-positive, rod-shaped, and facultatively anaerobic—they can grow with or without oxygen. They do not produce endospores.

All flashcards

What are key structural and physiological traits of Listeria species?
They are Gram-positive, rod-shaped, facultatively anaerobic, catalase-positive bacteria that do not form endospores.
Which Listeria species is the major human pathogen?
Listeria monocytogenes causes most cases of human listeriosis.
How can Listeria spread from one host cell to another?
ActA promotes actin polymerization, propelling the bacterium into a membrane protrusion that a neighboring cell can engulf.
Where can Listeria monocytogenes occur?
It occurs in environments such as soil, water, plants, and animals, and in foods including meats, produce, dairy, and processed foods.
What does refrigeration do to Listeria in food?
It slows bacterial growth but does not reliably eliminate the bacteria.

Quiz questions

  1. Which group includes people at increased risk of serious listeriosis?Answer: Pregnant women, newborns, older adults, and immunocompromised people
  2. What role does listeriolysin O play during Listeria monocytogenes infection of a host cell?Answer: It disrupts the membrane surrounding the bacterium in the phagolysosome.
  3. Which host-cell receptor does internalin A bind during Listeria monocytogenes invasion?Answer: E-cadherin
  4. What does ActA enable Listeria monocytogenes to do inside host cells?Answer: Recruit host actin to propel itself through the cell.
  5. How does refrigeration below 4 °C affect Listeria in food?Answer: It discourages growth but does not guarantee elimination.

Based on the Wikipedia article Listeria, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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