This can happen for some STDs but is rare. Syphilis can be acquired genitally, but the secondary stage can have infectious areas (called mucous patches) in the mouth or throat. Some oral HPV infections may result from auto-inoculation, i.e. transfer of infection from one's own genital area to the oral cavity. In theory, genital gonorrhea, chlamydia, or herpes might also be auto-inocluated to the oral cavity -- but if this happens, it is extremely rare. For all practical purposes, if you don't perform oral sex on a potentially infected partner, you can be confident you don't have any STDs of the throat or mouth.

I hope that helps. Let me know if anything isn't clear.

HHH, MD