Question

Listeria is dangerous because it:

• A. Produces spores
• B. Grows at refrigeration temperature
• C. Requires oxygen
• D. Is heat resistant

Hint:

Listeria monocytogenes is the classic "refrigerator pathogen."
Regular sanitation and strict shelf-life controls for chilled, ready-to-eat foods are critical to prevent listeriosis.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks why the foodborne pathogen Listeria (specifically Listeria monocytogenes) is particularly dangerous in food processing and preservation.

Step 2: Key Concepts and Approach:
Refrigeration is a primary method used to extend the shelf life of perishable foods by slowing microbial growth.
Pathogens that can bypass this cold hurdle are of serious concern to food safety.

Step 3: Detailed Explanation:

• Psychrotrophic Nature: Listeria monocytogenes is a psychrotrophic bacterium.
Unlike most foodborne pathogens (like Salmonella or E. coli), which stop growing at temperatures below $4^\circ\text{C}$, Listeria can actively multiply at refrigeration temperatures ($0\text{--}4^\circ\text{C}$).

• Risk in Ready-to-Eat Foods: This capability makes it dangerous in refrigerated, ready-to-eat foods such as deli meats, soft cheeses, and unpasteurized milk.
Even if initial contamination levels are low, long-term cold storage allows the population to rise to dangerous levels.

• Other Characteristics: Listeria is non-spore-forming and is easily killed by standard pasteurization temperatures, meaning it is not highly heat-resistant.
It is a facultative anaerobe, meaning it can grow with or without oxygen.

Step 4: Final Answer:
Listeria is dangerous because it grows at refrigeration temperature, matching Option (B).