Marker of fecal contaminatin is –
**Core Concept**
Fecal contamination is a critical concern in clinical settings, particularly in surgical and medical procedures. **Enterobacteriaceae**, a family of gram-negative bacteria, are often used as indicators of fecal contamination due to their abundance in the gastrointestinal tract.
**Why the Correct Answer is Right**
The correct answer is a type of Enterobacteriaceae that is commonly found in the feces of humans and animals. **Escherichia coli (E. coli)** is a gram-negative bacterium that is a normal inhabitant of the human gut but can also be a pathogen in certain situations. E. coli is used as a marker of fecal contamination because it is easily detectable and can indicate the presence of other pathogenic organisms.
**Why Each Wrong Option is Incorrect**
* **Option A:** **Staphylococcus aureus** is a gram-positive bacterium that can be found on the skin and mucous membranes but is not typically used as a marker of fecal contamination.
* **Option B:** **Klebsiella pneumoniae** is a gram-negative bacterium that can be found in the environment and on the skin but is not as commonly associated with fecal contamination as E. coli.
* **Option C:** **Pseudomonas aeruginosa** is a gram-negative bacterium that can be found in the environment and on the skin but is not typically used as a marker of fecal contamination.
**Clinical Pearl / High-Yield Fact**
Remember that E. coli is a normal inhabitant of the human gut, but its presence in a sterile environment or in a wound can indicate fecal contamination. A high E. coli count can also indicate a higher risk of infection in surgical patients.
**Correct Answer: D. Escherichia coli**