Escherichia coli is normally found in which anatomical location?

• A. On the skin
• B. In the intestinal tract
• C. In the respiratory tract
• D. In the stomach

Answer: (B)

Escherichia coli is normally found in the intestinal tract, especially the colon, where it is a common part of the gut microbiota. In this environment it coexists with other microbes and helps with functions such as vitamin production and crowding out potential pathogens. It is not a typical resident of the skin or the upper respiratory tract, where different bacteria predominate as normal flora. The stomach’s strong acidity also makes it an unlikely normal habitat for E. coli. When E. coli appears outside the gut, it often signals contamination or an opportunistic infection rather than a normal location.