system
Given the following post, respond as if you're commenting on Reddit:
human
Considering the massive amount of bacteria in feces, why don't people with bleeding hemorrhoids and fissures get serious infections?
gpt
Fecal bacteria are generally not good at surviving outside of the intestine.  They can't survive well in the presence of oxygen (even room air concentrations), and they do not have many specialized mechanisms to escape from immune cells in the blood.  A small amount of rectal bleeding generally does not cause a problem.  

However repeated rectal bleeding can lead to complications  Sometimes bowel cancer is detected when you find a certain type of fecal bacteria growing on a heart valve.