When  people get a cut in their skin, the bugs have direct access to the
blood, and patients should be dying of bacteriaemia and sepsis, but they
don't.

Why? Because people have an immune system. The blood is filtered by the
spleen and the liver (the liver has immune cells called "Kuppfer" cells that
are macophages, white blood cells that eat up bacteria). The blood sends in
white blood cells to fight any infection that may arise.  This applies to
anywhere in the body where there is cut or infection.

The intestines, especially the large intestine has a rich supply of blood.
The blood supply means that white blood cells can go anywhere bacteria
invade. In addition, large intestine has Peyer's patches, which are like
lymph nodes in the intestinal wall. Plus, the Kuppfer cells in the liver get
the bacteria before they can enter the circulation outside the GI tract
(almost all of the blood that comes from the GI tract enters the portal
circulation and goes through the liver before it goes into the general
circulation -- I think only blood from the mouth, throat and some parts of
the rectum is drained through the circulation that does not enter the portal
system and instead goes right into the general circulation).

In fact, rectal surgery, like for hemorroids is relatively free of post op
infections, something you might not expect consider that all of the poop
with lots of bacteria exit through the rectum.  And other conditions that
are associated with bleeding, like anal tears and polyps, also have a very
low rate of infection, because of the blood supply and rich amount of immune
cells ready to fight infection.

If you need more information, I think there is a great site for you:
www.google.com. Enter  intestine + immune system to learn more. They will
give you the straight poop on why bacteria in poop doesn't cause as many
infections are you might think.

Jeff