What percentage of normal enteric flora are anaerobes?

What percentage of normal enteric flora are anaerobes?

• A. >99%
• B. >99.9%
• C. >95%
• D. >90%

Answer: (B)

The enteric flora in the gut is almost entirely composed of anaerobic bacteria. The intestinal lumen, especially the colon, is extremely low in oxygen because any available oxygen is rapidly consumed by the resident microbes and the mucosal environment, creating conditions where obligate anaerobes thrive and predominate. A small minority of bacteria are facultative anaerobes, meaning they can grow with or without oxygen, but they constitute only a tiny fraction of the total population. Because of this, the percentage of normal enteric flora that are anaerobes is essentially all of them, typically cited as greater than 99.9%. The other options are too low because they don’t reflect how dominant anaerobes are in the gut ecosystem.

The enteric flora in the gut is almost entirely composed of anaerobic bacteria. The intestinal lumen, especially the colon, is extremely low in oxygen because any available oxygen is rapidly consumed by the resident microbes and the mucosal environment, creating conditions where obligate anaerobes thrive and predominate. A small minority of bacteria are facultative anaerobes, meaning they can grow with or without oxygen, but they constitute only a tiny fraction of the total population. Because of this, the percentage of normal enteric flora that are anaerobes is essentially all of them, typically cited as greater than 99.9%. The other options are too low because they don’t reflect how dominant anaerobes are in the gut ecosystem.