Increased level of which of the following indicates contamination of water
**Core Concept**
The question is testing the student's knowledge of waterborne pathogens and the indicator organisms used to detect water contamination. An indicator organism is a microorganism that is used to detect the presence of other, potentially harmful microorganisms in a given environment. In this context, the correct answer is a type of bacteria that is commonly used as an indicator of fecal contamination in water.
**Why the Correct Answer is Right**
The correct answer is **E. Escherichia coli (E. coli)**. E. coli is a gram-negative, rod-shaped bacterium that is commonly found in the intestines of humans and animals. It is a member of the Enterobacteriaceae family and is often used as an indicator of fecal contamination in water because it is found in high concentrations in human and animal feces. The presence of E. coli in water indicates that the water has been contaminated with fecal matter, which may contain other pathogens such as viruses, parasites, and bacteria.
**Why Each Wrong Option is Incorrect**
* **Option A:** Staphylococcus aureus is a gram-positive bacterium that can be found on the skin and in the noses of healthy individuals. While it can be a pathogen, it is not typically used as an indicator of fecal contamination in water.
* **Option B:** Pseudomonas aeruginosa is a gram-negative bacterium that can be found in a variety of environments, including water. However, it is not typically used as an indicator of fecal contamination in water.
* **Option C:** Klebsiella pneumoniae is a gram-negative bacterium that can be found in the respiratory tract and in the environment. While it can be a pathogen, it is not typically used as an indicator of fecal contamination in water.
**Clinical Pearl / High-Yield Fact**
It's worth noting that other indicator organisms, such as fecal coliforms and enterococci, can also be used to detect fecal contamination in water. However, E. coli is one of the most commonly used and widely accepted indicators of fecal contamination.
**Correct Answer: D. Escherichia coli (E. coli)**