To answer your questions:
1) Possible, but less likely. E Coli is not a common organism of the mouth.
2) That can vary from patient to patient. It would also depend on what bug is growing as well as any anatomical considerations.
3) Risk of transmitting HIV via oral sex is very low. However, if this is a concern, I would consider being tested now and in several months.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.