Question

The organism which is NOT an indicator of fecal pollution is

• A. Staphylococcus
• B. Streptococcus
• C. E.coli
• D. Clostridium perfringens

Hint:

True fecal indicator organisms live mainly in the gut, not on the skin.

Answer 1

The Correct Option is A

Testing water for fecal pollution relies on specific bacteria that live in the gut and are shed in stool. This question asks which listed organism does not belong to that group.

1. Staphylococcus: This organism lives mainly on skin and in the nose, not in the gut. It can end up in water through human contact, but that does not make it a reliable marker of feces reaching the water, so this is the exception.
2. Streptococcus: The fecal streptococci, such as Streptococcus faecalis, live in the human intestine and are a standard, well accepted indicator of fecal pollution, often used alongside E.coli testing.
3. E.coli: This is the gold standard indicator organism for fecal contamination, since it lives almost only in the gut of humans and warm blooded animals and appears in huge numbers in stool.
4. Clostridium perfringens: Its spores are tough and can survive in water long after the original contamination event, so it is useful for picking up fecal pollution that happened in the past or only now and then.

Three of the four organisms live in the gut and are directly tied to fecal shedding, while Staphylococcus belongs to the skin flora instead.

So the organism that is not an indicator of fecal pollution is Staphylococcus.