NGU/NSU and "normal oral bacteria"

I have read that once all other germ tests (trich, C&G, HSV..) for symtoms (symptoms) of NGU/NSU come back negative, the cause of said symptoms are often attributed to "normal oral bacteria" from the partner's mouth infecting the penis, followed by appropriate antibiotical treatment, and alls well that ends... well, STD symptom-free.

I have several questions though.

1. What the heck is "normal" oral bacteria?

2. And if the person who has this bacteria gave you NGU from performing oral (i.e. penis in their mouth and throat), does this mean you can never have unprotected oral with them, because their "normal" oral bacteria will infect your urethra every time??

3. Does this person just have a particularly "dirty" mouth that you should keep your penis (unprotected) out of?

4. If they are suggested to receive treatment (antibiotics), will their "normal" oral bacteria forever be wiped out? If it's "normal" oral bacteria, shouldn't that mean it can be dampened during treatment, but won't be eradicated?

5. Does the bacteria in ones mouth constantly change?

6. Is it possible their mouth could be particularly "dirty" one day, but not others, and if you received oral from them on that day, you'd get NGU, but would not get NGU on the other days?

It seems many things I've read tend to be resolved by, "it must have been "normal" oral bacteria, so take antibiotics and have a nice day", and I hope we can go a little further by getting some of these questions answered.

Hopefully other people are wondering about this too, and if you have any answers, please respond to them by #.

[gracefromHHP]

our bodies are covered in bacteria.  what is normal flora in the mouth and causes no illness there, isn't always so normal when introduced into the urogenital tract. It's not that the person is "dirty" or anything like that, it's just we are all different and what might not cause one person any illness, can cause another to become sick.  we don't treat anyone for "normal" mouth flora.  

if it seems to be a reoccurring problem for a couple, we recommend protected oral sex to eliminate it.

grace