Certified Surgical Technologist (CST) Practice Exam

Which organism is a normal resident flora of the intestinal tract?

1. Escherichia coli

2. Staphylococcus aureus

3. Pseudomonas aeruginosa

4. Clostridium tetani

The correct answer is: Escherichia coli

Escherichia coli is considered a normal resident flora of the intestinal tract, particularly in the large intestine. This bacterium plays a critical role in the digestive processes and helps maintain the balance of gut microbiota. E. coli contributes to the breakdown of food, aids in synthesizing vitamins such as vitamin K, and serves as a barrier against pathogenic organisms by competing for resources and space. In contrast, the other organisms listed are not typically part of the normal intestinal flora. Staphylococcus aureus is primarily found on the skin and mucous membranes and is associated with infections when it enters the bloodstream. Pseudomonas aeruginosa is an opportunistic pathogen commonly found in the environment and poses a risk in hospital settings rather than being a normal gut inhabitant. Clostridium tetani is known for causing tetanus and is not normally present in the healthy gastrointestinal tract.