I googled Ureaplasma and here is the basis of the article that could answer one of your questions:
"If cervical cultures for ureaplasma and mycoplasma are positive, both the patient and her sexual partner are usually treated with antibiotics such as doxycycline. As these bacteria may have been present for many years without causing any symptoms, the finding of ureaplasma and mycoplasma on cervical cultures does not in any way indicate infidelity or sexual misconduct."
Another short answer regarding Gardnerella:
"Gardnerella vaginitis is a common vaginal bacterial infection that affects three out of four women at least once in their lives and usually accompanies either a yeast, trichomonas or urinary tract infection. Men can be infected through sexual intercourse and can also transmit to additional partners.
Read more: http://www.ehow.com/about_5081922_gardnerella-vaginitis.html#ixzz2atAgvgk5"
Hope some of this eases your mind some.
I do not know much about these, you can probably find as much info as me by using google, or you can pay to post in the Expert forum.