Which of the following is commonly found as part of the resident flora of the human intestines?

• A. Streptococcus pyogenes
• B. Staphylococcus aureus
• C. Mycobacterium tuberculosis
• D. Escherichia coli

Answer: (D)

Verified step by step guidance

1. Understand the concept of resident flora: Resident flora, also known as normal microbiota, refers to the microorganisms that normally live on or within various parts of the human body without causing disease under normal conditions.
2. Identify the environment in question: The problem asks about the resident flora of the human intestines, which is a complex ecosystem with many bacterial species adapted to that environment.
3. Review the characteristics of each listed microorganism: Streptococcus pyogenes is typically found in the throat and skin and is often associated with infections; Staphylococcus aureus is commonly found on the skin and nasal passages; Mycobacterium tuberculosis is a pathogen causing tuberculosis and is not part of normal flora.
4. Recognize that Escherichia coli is a well-known, common resident of the human intestinal tract, where it plays a role in digestion and maintaining gut health, making it a typical example of intestinal resident flora.
5. Conclude that among the options, Escherichia coli is the correct choice as it is commonly found as part of the resident flora of the human intestines.