Question

Among the following, the Faecal indicator organism is

• A. Staphylococcus aureus
• B. Escherichia coli
• C. Vibrio cholera
• D. Listeria monocytogens

Hint:

In microbiology, the term "Coliforms" (specifically Faecal Coliforms) is synonymous with faecal contamination. E. coli is the gold standard for testing the microbiological safety of drinking water and seafood.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify which microorganism is used as a standard "indicator" to detect faecal contamination in water or food products. An indicator organism is used because testing for every possible pathogen is impractical and expensive.
Detailed Explanation:

• Criteria for an Indicator Organism: A good faecal indicator should be present whenever pathogens are present, absent in unpolluted samples, and have a survival rate similar to pathogens. It should also be easy to isolate and identify.

• Escherichia coli (E. coli): E. coli is the most common and widely used faecal indicator. It is a natural inhabitant of the intestines of warm-blooded animals and humans. Its presence in high numbers in water or fishery products is a direct indication of recent faecal contamination and suggests the potential presence of enteric pathogens like Salmonella or Shigella.

• Evaluation of other options:
• Staphylococcus aureus: Indicates contamination from human handlers (skin, nose, wounds).

• Vibrio cholerae: Is a specific pathogen (causing cholera) but not used as a general "indicator" of faecal pollution.

• Listeria monocytogenes: An environmental pathogen often found in processing plants; it is not specifically indicative of faecal matter.

Step 2: Final Answer:
Escherichia coli is the standard faecal indicator organism.