Which set lists the predominant flora of the colon?

Which set lists the predominant flora of the colon?

• A. Coliforms, Enterococcus, Anaerobes, and Streptococci
• B. Staphylococcus aureus, Streptococcus, Enterococcus
• C. Escherichia coli only
• D. Bacteroides fragilis and Clostridium difficile

Answer: (A)

The colon is home to a mixed microbial community that is mainly anaerobic, with a substantial presence of facultative anaerobes such as coliforms (including E. coli) and Enterococcus, along with other organisms like streptococci. This combination—coliforms, Enterococcus, anaerobes, and streptococci—best reflects the typical, healthy colonic flora, which is dominated by anaerobes but also contains these facultative members in normal numbers. Why the other options don’t fit: Staphylococcus aureus is not a major component of normal colonic flora. Clostridium difficile is not a routine part of the normal flora and is typically associated with antibiotic disruption and disease rather than everyday colonization. Naming Escherichia coli alone misses the major anaerobic groups and other facultative organisms like Enterococcus and streptococci. Pairing only Bacteroides fragilis with Clostridium difficile omits several key facultative organisms and includes a pathogen (C. difficile) rather than a representative normal flora member.

The colon is home to a mixed microbial community that is mainly anaerobic, with a substantial presence of facultative anaerobes such as coliforms (including E. coli) and Enterococcus, along with other organisms like streptococci. This combination—coliforms, Enterococcus, anaerobes, and streptococci—best reflects the typical, healthy colonic flora, which is dominated by anaerobes but also contains these facultative members in normal numbers.

Why the other options don’t fit: Staphylococcus aureus is not a major component of normal colonic flora. Clostridium difficile is not a routine part of the normal flora and is typically associated with antibiotic disruption and disease rather than everyday colonization. Naming Escherichia coli alone misses the major anaerobic groups and other facultative organisms like Enterococcus and streptococci. Pairing only Bacteroides fragilis with Clostridium difficile omits several key facultative organisms and includes a pathogen (C. difficile) rather than a representative normal flora member.