Escherichia coli
EPI-Net Perspective , 1 , 2007

Carrero-Colon, M., Turco, R.F.

Over the past year it seems the bacteria E.coli is everywhere. You have heard about them in news reports, it seems every day somebody is getting sick from eating undercooked hamburger meat, contaminated food or from swimming in contaminated water. But do all E. coli cause disease? The answer to this question is NO; in fact most E. coli bacteria are harmless or beneficial. For example, E. coli in the large intestine of humans is beneficial since it manufactures vitamin B12 while you digest food (2). So why the concern with this bacterium? The general answer is simple: there are two broad categories of E. coli, those that cause no harm but are used to indicate other possible problems and those that are capable of causing a disease. Bacteria are small (1 μm in length) unicellular organisms that can live independently of a host. For example, because of their small size, a gram of soil can often contain over a billion bacteria. They have colonized a variety of environments ranging from the gut of a termite and most humans to Lake Michigan and beyond.