In doubtful cases, the presence of which organism confirms the fecal contamination of Water –
**Core Concept**
The presence of fecal coliform bacteria in water indicates fecal contamination, as these organisms are commonly found in the human gastrointestinal tract. Fecal coliforms are used as indicators of water quality due to their presence in the feces of warm-blooded animals, including humans.
**Why the Correct Answer is Right**
The organism that confirms fecal contamination of water is _Escherichia coli_ (E. coli), a type of fecal coliform bacteria. E. coli is a gram-negative, rod-shaped bacterium that is widely distributed in the human gut and is often used as an indicator of fecal contamination in water due to its presence in the feces of warm-blooded animals. The presence of E. coli in water suggests that the water has been contaminated with fecal matter, which can pose a risk to human health.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, but if it's a distractor, it might refer to another type of bacteria, such as _Pseudomonas aeruginosa_. However, _Pseudomonas_ is not typically used as an indicator organism for fecal contamination.
* **Option B:** This option is also not specified, but if it's a distractor, it might refer to another type of bacteria, such as _Klebsiella pneumoniae_. However, _Klebsiella_ is not typically used as an indicator organism for fecal contamination.
* **Option C:** This option is also not specified, but if it's a distractor, it might refer to another type of bacteria, such as _Staphylococcus aureus_. However, _Staphylococcus_ is not typically used as an indicator organism for fecal contamination.
**Clinical Pearl / High-Yield Fact**
E. coli is a common cause of urinary tract infections (UTIs) and can also cause gastrointestinal infections, such as traveler's diarrhea. It is also used as a model organism in molecular biology and genetics.
**Correct Answer: C. Escherichia coli**