Question

Which organism is psychrotrophic?

• A. Salmonella
• B. Listeria
• C. Bacillus
• D. Clostridium

Hint:

Listeria is the classic example of a psychrotrophic foodborne pathogen.
Always assume that cold storage alone is not sufficient to control this organism.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify which of the listed bacterial genera is classified as psychrotrophic (capable of growing at low/refrigeration temperatures).

Step 2: Key Concepts and Approach:
Psychrotrophic organisms are mesophilic microbes that have adapted to grow at cold temperatures ($0\text{--}7^\circ\text{C}$), although their optimal growth temperature is higher ($20\text{--}30^\circ\text{C}$).
These organisms are a major concern in the storage of chilled and refrigerated foods.

Step 3: Detailed Explanation:

• Psychrotrophic Pathogens: Listeria monocytogenes is a prominent foodborne pathogen with psychrotrophic capabilities.
It can survive and multiply in refrigerated facilities, on processing equipment, and within packaged food items stored under cold conditions.

• Clinical Impact: This ability to grow at low temperatures allows Listeria to reach infectious doses in ready-to-eat foods over normal storage periods, posing a severe threat to pregnant women, newborns, and immunocompromised individuals.

• Other Organisms: Most strains of Salmonella, Bacillus, and Clostridium are mesophilic or thermophilic, requiring warmer temperatures to grow.

Step 4: Final Answer:
Thus, Listeria is the psychrotrophic organism among the choices, matching Option (B).