We are not isolated organisms and we carry around with us many different types of microbes while remaining perfectly healthy. This BBC news article highlights some of the interesting snippets from research investigating our microbial populations.
As with all things, it is about balance, and maintaining a good balance between microbial populations can be fairly important. For example, taking antibiotics can kill friendly bacteria all over the body, leading to a common yeast infections such as Thrush. The reduction in bacteria that keep the normal yeast population in check can trigger a population explosion, leading to irritating consequences on skin and mucous membranes. Bacteria are part of our health and well being, as are the other microbes in our systems. Even those that could become dangerous are generally found in low levels in a healthy individual.
I particularly like this quote:
Skeptical kinkster musing on whatever takes my fancy!