Chapter 20.L2, Problem 1CT

What is the logic behind testing for E. coli to detect fecal contamination of water?

Summary Introduction

To determine:

The logic behind testing for E. coli to detect fecal contamination of water.

Introduction:

E. coli is a common inhabitant of the human intestine; it is also able to survive in the outside environment.

Explanation of Solution

Coliforms such as E. coli are used to detect fecal contamination in water samples due to their widespread presence in the human intestine. They are able to survive in the outside environment, and will therefore provide a reasonable inoculum for culture tests. They are also easier to culture than true pathogens. For this reason, they are used as the initial indicator for fecal contamination; their presence indicates the possible presence of true enteric pathogens such as Salmonella.

Conclusion

E. coli is used to detect fecal contamination in water due to the fact that it is a prominent inhabitant of the human intestine, it is able to survive in the environment and it is easier to culture than true enteric pathogens.