Trace amounts of your own E.coli strains are not like to get you sick. Unless you touch food and give them a place to incubate. But trace amounts can really make others sick. Especially the O157 strain. Difficult to treat and exposure to as few as 10 bacteria can be fatal. Somebody touching the rim of a glass or an apple…
Also, for good measure, the poster child for poor hand hygene, Typhoid Mary.
:o 
Regarding the question of whether the human body can be bacteria free (e.coli or other) the answer is a resounding NO. The human body has ten times more bacteria cells than it does of its own cells. (Human microbiome - Wikipedia) Although because bacteria cells are so much lighter than human cells, they make up only a few pounds of the body weight.
If certain areas of the body (particularly the Mouth and Vagina) are bacteria free they become infested with other infective organisms which are normally out performed by the bacteria for resources. The digestive system if cleared of many of its bacteria also becomes ineffective. These effects often follow aggressive anti-biotic treatment that not only kill infective organisms but all of the useful ones as well.
I am extremely skeptical coming in contact with a few of your own e.coli strains will harm you, unless as said you let them multiply in an outside medium first.
As far as I am aware it doesn’t matter how clean you are, if you cohabitate like a family you’re going to start sharing your gut biomes. Sorry.
Ten points to Pjen. Bacteria are essential for our biological processes. Each part of the human body has a colony of bacteria which lives in benign symbiosis and protects that part. Interestingly each of us have slightly unique colonies which is why bacteria from another person can make you sick.
So…you can get sick of you own “sh*!”???