Thank you for the answers you have provided and I have spent some time reading cases related to mine. However, the anxiety cannot be eliminated and I think the best way to alleviate it is to ask a question myself. Long story short:

Background: Had a protected oral sex with a CSW (Female) in Amsterdam 37 days ago. She was said to be tested 26 days before the sexual activity and the results were all negative. No other sexual activities involved. The total duration was about 10 mins, with my penis in her mouth for about 2-3 mins. The condom should be intact as no leakage was observed at the tip and was intact in other parts of it. Took Gonorrhea / Chlamydia/Syphilis/HIV blood and urine tests 21 days after exposure, all negative.  

Questions:

1. I am super anxious about the possibility of being infected by syphilis. Although I have read through many of your answers that conclude that the acquisition of syphilis even by unprotected oral is very very rare, I am still worrying and often thinking that the condom might fail to prevent the syphilis bacteria from entering. So based on your decades of experience of dealing with STIs, have you ever encountered cases where the patient got infected after a protected oral sex, even if the condom was intact?

2. So far (37 days post exposure) I haven't noticed any chancre on my penis. I remember that you mentioned a chancre would usually appear 2-3 weeks after exposure, so does this provide a strong evidence that I was not infected?

3. I once used 800 mg cefdinir for treating an ulcer in my mouth that appeared 6 days after exposure (almost sure that it had nothing to do with syphilis).  Will this amount of cefdinir help with preventing possible syphilis infection?  

Thank you for your response. 

 

Honestly, you're overreacting to a nearly zero risk situation. First, my understanding is that syphilis frequency in the regulated CSWs in Amsterdam (and most of those who don't participate in the regulation procedures) is very low. (You could consider confirming this with a call or email to Amsterdam's world class STI clinic (called GGD -- I forget what the letters mean in Dutch). Second, with your partner having been tested 4 weeks earlier, the chance she had active syphilis is near zero. Third, with condom protected oral sex the risk of syphilis was zero even if she was infected. Fourth, if you had acquired syphilis, by now almost certainly you would have had a very noticeable chancre -- syphilitic ulcer -- on your penis (probably above the condom line). Finally, although 3 weeks is early for conclusive syphilis blood test results, that negative result is around 70-80% reliable. And to answer your opening question:  In my 50 years in the STD business, I have never seen nor even heard anyone acquired syphils during a condom protected oral exposure.

To your specific questions:

1. Your objective analysis is exactly right. You just have to accept it from an emotional/psychological perspective.

2. Above I was referring to chancre within 3 weeks. Five weeks is even better.

3. There are few if any data on cefdinir and syphilis, but it certainly is active against Treponema pallidum, the cause of syphilis. Taking it at 6 days further reduced your virtually zero chance of having syphilis.

If somehow I had been in your situation, I would never have worried and certainly would not have had a syphilis blood test. However, having started down that path, for reassurance you probably should have another one now (or whenever you pass 6 weeks after the event). If you do it, you can count on another negative result.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

1. Will syphilis bacteria enter the body via intact skin or mucous membranes? Damaged ones surely will increase the chance, but I fear that an infection is also possible with good skin conditions.

2. Just to be sure, syphilis bacteria cannot pass through a condom, even if it is lubricated by lubricant?

2. Correct.

3. I cannot say more than I did above (previous answer no. 3. For prevention soon after exposure, I would expect it to be 100% protective.

Since you remain concerned despite all we have discussed, go ahead with a syphilis blood test at 7 weeks as you are planning. When you receive the negative result, just move on.

1. Based on your experience, how common is a syphilis chancre developed in the mouth/on the lips, among all those who have syphilis chancres? Can it be less than 20%?

2. Have you seen cases where a chancre formed rather lately, say, after 5 weeks? How common will be that?

These will be all of my questions. Thank you for your help and sorry for the inconvenience caused by my anxiety. 

Try going back and carefully reading all your questions and my replies above. You should now be worry free. Your 7 week test will be negative.

As you anticipated, that concludes this thread. Please do not be tempted to post another about these concerns. But I'll make a deal with you:  if your next test is positive for syphilis, please start a new question to let us know and we will refund your posting fee. In the meantime, best wishes and stay safe.