Urethritis question

I am a straight female.  I recently slept with a guy a couple times in the past 8 weeks or so, using condoms everytime.  We did have oral sex without protection (both ways).  He was diagnosed with urethritis at some point during this time.  He says I'm the only one he's slept with in the past couple months, and that he tested negative for any STDs. After first developing the symptoms, he took antibiotics and abstained from sex for about a week, but the symptoms returned after sleeping with me again.  (He's now being treated again).  I also tested negative for chlamydia and gonnorhea (Gonorrhea), although the doctor told me to take zithromax just in case.  Realistically, what are the chances that his urethritis symptoms were caused by the condom or lube we used (liquid silk, which contains parabens).  If there was some kind of non-STD bacteria passed orally or with the condom, what could have caused this and how do we prevent it in the future?  If there is some kind of STD involved here, what are the chances it passes orally, and in terms of who's going down on who?  Even though I am negative for chlamydia and gonnorhea (Gonorrhea), could there be some other STD I have that is causing him to have these recurring symptoms?  In short, I find it hard to believe that his 2 bouts of urethritis have occured while we both are testing negative for STDs, so I wonder whether one of us unknowingly has been exposed to an STD.  All the research of done indicates that this is "rare" but I need a little more context, is it rare like it happens one in a million times or one in one hundred?
Thanks!

[H. Hunter Handsfield, M.D.]

Welcome to the STD forum.  I'll try to help.

Your doctor was correct to treat you, and azithromycin (Zithromax) is one of the recommended drugs.  You really should have been treated the first time your partner developed nongonococcal urethritis (NGU).

You can find quite a bit of information about NGU on this forum; just enter that term (or spell out nongonococcal urethritis) in the search link.  NGU is the single most common STD in men, by a large margin.  About one third of cases are caused by chlamydia, but the specific cause in most cases is unknown.  Treatment of men's sex partners is routine.

In terms of your health, most likely there is no serious risk.  The mostly unknown causes of nonchlamydial NGU have not clearly been shown to carry any serious health risks for women.  On the other hand, the possibility of serious consequences cannot be ruled out and treatment is recommended both to protect the partner's health and to prevent reinfection of the male partner.

To the specific questions:

His infection came from you, not anything to do with the condom.  The cause was a sexually transmitted bacteria -- in other words, yes there is "some kind of STD involved here".  Oral transmission is a good bet; some cases of NGU in men are believed to be acquired that way, perhaps caused by bacteria that are entirely normal in the mouth and throat but cause problems in the urethra.  There is no reason to suppose you are at risk for any infection from a partner's oral bacteria, but there hasn't been any research in this area so I can't say for sure there is no risk.

From those response, I hope you no longer "find it hard to believe" that your partner's NGU occurred in the absence of recognized STDs like gonorrhea and chlamydia. This is anything but "rare".  It happens all the time -- as I said, it is the single most common disorder seen in STD clinics.  

Bottom line:  Don't worry too much about this; it is unlikely either you or your partner will have any serious health problems from it.  Take the treatment as prescribed, then move on.  All will be well.

Best wishes--  HHH, MD