Which organism is primarily identified in fecal coliform tests?

The organism primarily identified in fecal coliform tests is Escherichia coli. This specific bacterium is a key indicator of fecal contamination in water sources. The reason E. coli is used as a standard in these tests is due to its significant presence in the intestines of humans and warm-blooded animals, making it a reliable marker for fecal matter.

Detection of E. coli in water suggests that there may be a presence of pathogens that can cause illness. Consequently, E. coli serves as a practical tool to assess the safety of drinking and recreational water, indicating potential health risks due to contamination.

In contrast, the other organisms listed are pathogenic bacteria associated with specific diseases but are not general indicators of fecal contamination. Salmonella typhi is known for typhoid fever, Shigella flexneri causes dysentery, and Vibrio cholerae is responsible for cholera. While these organisms can indicate the presence of pathogens in contaminated water, they are not specifically associated with routine fecal coliform testing, which is why E. coli is the primary focus.