Escherichia coli (E. coli), discovered by Theodor Escherich in 1885, is commonly found in the intestines of humans and animals, playing a vital role in maintaining intestinal health. While most strains are harmless, some can cause illness, especially in those with weakened immune systems. E. coli became important as an indicator of fecal contamination in 1892 due to its prevalence in feces and its ability to ferment glucose and later lactose, making it easier to detect.

However, distinguishing E. coli from similar bacteria was challenging, leading to the introduction of the term “coliform.” Despite its widespread use, uncertainty remained about its association with contamination, prompting the distinction of fecal coliforms, primarily E. coli, from other coliforms. Newer identification methods have reinforced E. coli’s role as an indicator of fecal contamination, despite challenges in differentiation from similar bacteria like Klebsiella.

The attached material contains official guidelines for enumeration of E. coli and coliform bacteria.