All of the tests came back negative/non-reactive with the exception of Chlamydia.  I have an appointment in the next few days with a physician where I assume I will be prescribed antibiotics for the Chlamydia.  My research leads me to believe it will be 1g of Azithromycin, but obviously, I'll follow doctor's guidance.

Assuming no other exposures and compliance to the doctor's orders on the Chlamydia prescription, are there any other future actions I should take?  

My research turns up differing results on the question of re-testing for Chlamydia post-treatment (some say to test for proof-of-cure, others for non-recurrence, others say no followup testing needed).  Do I need to re-test for Chlamydia post-treatment?  If so, at what time?

My research also seems to indicate that a 4th generation HIV test at 50 days post-exposure is completely conclusive.  Does the science completely support this conclusion?

Presumably the chlamydia was detected in your urine, or maybe a urethral swab? Either azithromycin or doxycycline is recommended. Azithro has the advantage of single-dose treatment, whereas doxy is twice daily for 7 days. If you're good at remembering to take pills, i.e. anticipate reliable completion of all doses, doxycycline is preferred. Azithromycin fails to cure 2-4% of genital chlamydial infections, whereas doxy is 100% reliable. If "unprotected anal" means you were the receptive (bottom) partner and your positive test is from a rectal swab, then definitely do not take azithro, which fails to cure up to 20% of rectal chlamydia.

CDC and virtually all experts, including I and Dr. Hook, recommend that everyone with gonorrhea or chlamydia be retested 3-6  months after treatment. In addition to detecting occasional treatment failure, numerous research studies show that once somone has either of these STDs, statistically they are quite likely to be reexposed (often unknowingly) and reinfected in the next few weeks or months. If there is any reason to be partuclarly suspicious of treatment failure -- e.g. if you receive azithromycin but not doxy -- it is reasonable to have a test-of-cure 3-4 weeks after treatment. (This is not official but likely will become so with CDC's expected revised STD treatment guidelines later this year.) (For the past 30+ years, Dr. Hook and I have served on CDC's expert consultation panel for the STD guidelines.) However, test of cure generally should not be done sooner than 3 weeks after treatment. Even when chlamydia or gonorrhea bacteria are successfully eradicated, it takes up to 3 weeks for detectable DNA to clear out, giving false positive tests.

The answer to your closing question is yes:  The HIV antigen-antibody (AgAb, "4th generation") blood tests detect almost all infections by 4 weeks and 100% of them by 6 weeks. A negative result at 50 days is conclusive.

My final comment is to suggest you get into the condom habit for anal sex with other men. Perhaps you've already been kicking yourself about that lapse in sexual safety, especially if he was a new partner or someone known to have other partners himself. And finally that you were a bit overtested. After any single such exposure, testing for gonrrhea, chlamydia, syphilis and HIV generally are sufficient. All the others in the test panels offered by many labs are either too unlikely to be necessary or the tests are not completely reliable.

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

HHH, MD