Bacteria indicating fecal contamination are measured by which indicator?

• A. E. coli Indicator
• B. Enterococcus
• C. Coliforms
• D. Total Coliform Bacteria

Answer: (A)

The key idea is identifying a bacterium that specifically signals fecal pollution. E. coli lives in the intestines of humans and other warm-blooded animals, so its presence in water is a clear sign that fecal material has entered the system. Because E. coli is a more direct indicator of recent fecal contamination than broader groups, its detection is more closely linked to potential health risk from fecal-origin pathogens.

Coliforms, including total coliforms, include many environmental bacteria that can be present without any fecal input, making them less specific as indicators of fecal contamination. Enterococcus can also indicate fecal pollution and is useful in some contexts (like marine waters), but for a general, widely used freshwater fecal indicator, E. coli is the best choice.