[Question #7126] Chlamydia from oral sex?

8 months ago
Hi,

I recently received unprotected oral sex from a female on a Monday. Tuesday I ordered myself a urine test and doxycycline. I immediately started the course to tackle any potential virus.  On Thursday I sent my urine test of to the lab and received a ‘negative’ the following Monday. I since finished my course on the Tuesday (next day of receiving the results)

My question - even though research suggestA the incubation period is 7-14 days from exposure , I took the test a few days after AND started the antibiotics as an extra safe precaution. - what are the chances of contracting chlamydia from unprotected oral sex? And will my test be likely to be accurate given the antibiotics were taken 3 days before the test? 

Thanks 
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
8 months ago
Welcome to the forum. Thanks for your confidence in our services. 

Some questions can be answered based only on the titie, in this case "Chlamydia from oral sex?" For reasons that will become apparent, this is a topic that I am especially interested in, so I'm using this opportunity for a blog-like reponse that can be used in responding to future questions, in addition to yours. It may surprise you to hear this, but chlamydia from oral sex is very rare. Some infected persons believe that's how they were infected, but that doesn't constitute proof. I am very aware that many online sources and many health professionals believe and advise that oral sex is a chlamydia risk. But here are two key scientific facts.

1) Chlamydia doesn't take hold very well in the oral cavity, and therefore is uncommon. Until a few years ago, oral chlamydia was believed to be almost nonexistant. With newer and more accurate testing, we know it happens more than previously thought. But still, it is very uncommon. In fact, CDC and most experts advise against even testing throat swabs for chlamydia; it's too rare to be worth the time and money.

2) Among men with nongonococcal urethritis (NGU) following vaginal or anal sex, 30-40% test positive for chlamydia as the cause. Among men with NGU who only had received oral sex, chlamydia is found in 0-1%. (I was the lead researcher on two separate research studies with these findings. In my studies, it was 0% -- no such men had chlamydia.

In most ways, chlamydia and gonorrhea are very similar, both causing urethral, cervical, and rectal infections and easily transmitted from those anatomic sites. But the similarity with gonorrhea doesn't apply to oral infection and risk from oral sex. Gonorrhea readily infects the throat and frequently is transmitted to the penis of men receiving BJs from partners with oral infection. Chlamydia is not.

None of this means you could not have caught chlamydia from the exposure described, but it was extremely unlikely. There was no need for doxycycline, but if you had been exposed, treatment within 3 days or two would have aborted the infection. In other words, your negative test result proves you don't have it, but it cannot tell whether you were ever infected. In any case, you don't need any more chlamydia testing.

For all those reasons, you were at much higher risk of gonorrhea than chlamydia from this event. Taking doxycycline was a mistake:  unnecessary to protect against chlamydia, but not good enough to reliably cure gonorrhea (20-40% of gonorrhea strains are resistant to it). And by the way, the duration of doxy to cure chlamydia is 7 days; 14 days is never necessary. But I suggest you stop it immediately; then be on the alert for gonorrhea symptoms in the next several days.

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

HHH, MD



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8 months ago
Thank you for your swift and comprehensive reply, Doctor. 

From what you have replied my next question is - from what I have stated in my initial question, it is probably worth me mentioning that the test that came back negative was a test for BOTH chlamydia and gonorrhoea.  I have had zero symptoms also for gonorrhoea.

My question in short - what is the likelihood (taking into account my initial question) of receiving a ‘false’ positive from the test? 

Kind regards, 
8 months ago
.... for gonnorrhea
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
8 months ago
Yes, I assumed you also were tested for gonorrhea. Almost all gonorrhea/chlamydia testing is linked:  a test for either usually includes both. But unlike the situatation for chlamydia, doxycycline could suppress a positive gonorrhea infection, leading to a negative test result, without curing the infection. So although there is zero chance you now have chlamydia, there is still a slim possibility for gonorrhea. Dont' get me wrong -- this is extremely unlikely. But it could happen.

False positive tests for either gonorrhea or chlamydia are exceedingly rare. A positive result is always accurate, for all practical purposes.
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8 months ago
Thanks you Doctor. I feel reassured now. 

I suppose my final question is - how often is gonorrhoea transmitted from receiving oral sex from a female? You mentioned previously you were the lead on a study re chlamydia... is there a similar study/data re gonorrhoea?  Is this asymptomatic?

Thank you for your efforts in replying. I have appreciated these
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
8 months ago
Yes, there are many more studies on oral gonorrhea than oral chlamydia. Oral sex by a female partner is very low risk for urethral gonorrhea. Among women with gonorrhea,only 1-2% have oral infection (compared with 20-25% among men who have sex with men). Accordingly, oral sex accounts for a substantial minority of urethral gonorrhea in MSM, but is rare in men receiving fellatio from female partners.

That completes the two follow-up exchanges included with each question and so ends this thread. Thanks for the thanks; I'm glad to have been of help. Best wishes and stay safe.
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