The bacteria which decays the human body once it has died, is it in the body while the person is still alive and what is its name?

1) "The second stage of decomposition is bloating; bacteria in the gut begin to break down the tissues of the body, releasing gas that accumulates in the intestines, which becomes trapped due to the early collapse of the small intestine. This bloating occurs largely in the abdomen, and sometimes in the mouth and genitals. The tongue may swell. This usually happens in about the second week of decomposition. Gas accumulation and bloating will continue until the body is decomposed sufficiently for the gas to escape.
The third stage is putrefaction. It is the last and longest stage. Putrefaction is where the larger structures of the body break down, and tissues liquefy. The digestive organs, the brain, and lungs are the first to disintegrate. Under normal conditions, the organs are unidentifiable after three weeks. The muscles can be eaten by bacteria or devoured by carnivorous animals. Eventually, sometimes after several years, all that remains is the skeleton."

"When a corpse is buried, the body will decompose by the actions of anaerobic bacteria."
Source and further information:
http://en.wikipedia.org/wiki/Cadaver


2) "Organisms traditionally associated with transmission from cadavers include bloodborne viruses (HIV, hepatitis B, hepatitis C, human T-lymphotropic virus 1), enteric bacteria (Salmonella, Shigella, Campylobacter, Yersinia, Vibrio cholerae, Vibrio vulnificus, Escherichia coli, Leptospira), viruses (rotavirus, norovirus, hepatitis A virus and enteric adenovirus), parasites (Giardia, Cryptosporidium) and airborne agents (Mycobacterium tuberculosis)"
Source and further information:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2095048/


3) "With the human immune system permanently off-line, the digestive bacteria in the gut gain the upper hand, causing an upset in the uneasy intestinal alliance. These bacteria begin nibbling on the body itself. As the host’s cells steadily self-destruct from autolysis, their membranes rupture, spilling the nutrient-rich cell filling into the tissues. The bacteria thrive in this river of food, and they soon establish decomposition franchises at every extremity."
Source and further information:
http://www.damninteresting.com/the-remains-of-doctor-bass


4) Further information:
http://www.absoluteastronomy.com/topics/Decomposition
http://en.allexperts.com/e/d/de/decomposition.htm
http://en.wikipedia.org/wiki/Decomposition#Human_decomposition
http://en.wikipedia.org/wiki/Human_flora
http://en.wikipedia.org/wiki/Gut_flora