Which indicator organism is commonly used to signal fecal contamination in water testing?

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Coliform bacteria are used as the standard sign of fecal contamination because they are abundant in feces from humans and animals and are easy to detect with routine, rapid methods. Their presence in water signals that fecal material may be present, prompting further, more specific testing for actual pathogens. Protozoan pathogens like Giardia lamblia and Cryptosporidium require more complex concentration and microscopy methods and are not used as routine indicators. Enterococcus is another fecal indicator used in some programs, especially for recreational waters, but coliforms are the most widely used initial signal in many water testing schemes.