1. It was mentioned that syphilis is not transmissible within 3 to 4 weeks.  But I have seen in other posts that it can be transmissible around 10 days when a chancre appears. (I never had a chancre but worry about lesion that wasn’t visible) any clarity on this is helpful! I had sex with my wife 10 days after exposure ( I started doxycycline and cefixime a couple of days before we had sex) timeline in other post.

2. If I have negative RPR at 6 weeks, does that mean I never had transmissible syphilis? I am concerned that I could have transmitted syphilis before the antibiotics completely aborted syphilis. 

3. Is cefixime 800 mg 100 percent effective in aborting syphilis if it is given with 10 days of exposure?

Thank you!!!

1. It is true that syphilis is trnasmissible as soon as a chancre appears, about 10 days at the earliest. The possibility you had an incipient, as yet unnoticed chancre when you had sex with your wfie at 10 days is zero:  if you didn't have an obvious open sore, she was nto at risk.

2. Yes, your negative RPR proves you never had syphilils, transmissible or not. 

3. Yes, cefixime, like doxycycline, is 100% effective in aborting syphilis.

On top of all these details, you had a low risk exposure. Oral sex isn't completely risk free, but it's very low risk for syphilis even with a known infected partner -- and you provide no information to raise a strong suspicion your partner was infected.

Do your best to stop looking for arcane reasons that you could have infected your wife. 

HHH, MD

One last question for my knowledge:

Is there an agreed upon time frame that antibiotics must be started to abort syphilis? I have a read 2 to 3 days and I have also seen as long as it is started within 10 days? 

There is only one paper Dr. Hook and I co-authored (with several others) in which the words azithromycin and syphilis both appear. To my recollection, it says nothing to support your statement about effectiveness in aborting syphilis and time since exposure. https://pubmed.ncbi.nlm.nih.gov/8042129/

That concludes this thread. Please note the forum does not permit repeated questions on the same topic or exposure. This being your second, it should be your last about this exposure, syphilis risk, testing, etc, especially given the detail already addressed. Future onesmay receive no reply and the posting fee will not be refunded. This policy is based on compassion, not criticism, and to reduce temptations to keep paying for questions with obvious answers. In addition, experience shows that continued answers tend to prolong users' anxieties rather than reducing them. Finally, such questions have little educational value for other users, one of the forum's main purposes. Thanks for your understanding. I do hope the two discussions have been helpful.