In water safety testing, which organism indicates fecal contamination?

• A. Total coliforms.
• B. Campylobacter.
• C. Salmonella.
• D. E. coli indicates fecal contamination.

Answer: (D)

In water safety testing, we look for organisms that signal fecal pollution. Total coliforms are a broad group that can come from soil, vegetation, and animals, so their presence doesn’t prove fecal contamination by itself. Pathogens like Campylobacter and Salmonella are actual causes of illness and do indicate fecal sources, but they are not used as routine indicators because testing for them is more complex and less practical for regular monitoring. E. coli, on the other hand, is a specific type of fecal coliform that almost always originates from animal or human waste. Its presence in water is a direct and reliable sign of fecal contamination and suggests a higher likelihood that enteric pathogens may be present. That specificity makes E. coli the best indicator among these options for fecal contamination.