Trying to Make Sense of Positive Chlamydia Test Result

My girlfriend tested positive to chlamydia 9 months into our monogamous relationship.  She took the prescribed medication after which she re-tested negative.  The previous STD/STI tests were 18 months prior and during those 18 months she has only had two sexual partners including myself.  She never had any signs or symptoms of chlamydia infection.

Upon learning of her positive test to chlamyia, I had myself comprehensively tested and my test results all came back negative.  My girlfriend also contacted the immediately preceding boyfriend who advised that he was tested a few months after their relationship ended and he was also negative.

My girlfriend and I have engaged in unprotected sex, as I believe she did with her previous partner.

I am curious as to how it is possible that my girlfriend tested positive to chlamydia when neither of her two sexual partners during the period in which it would appear that he contracted the infection tested positive to it.

What is the likelihood that her chlamydia positive test result was false?  (By the way, I have no reason to suspect that our relationship hasn't been monogamous).

Thank you.

[serenmelyn]

I'm no expert but apparently chlamydia can lay doormat for over a year especially in women so maybe you're partner had it but seeing as it was doormat she may not have passed it to you or her previous partner, then after some time maybe something triggered you're girlfriends STD off and therefor that would make sense to what you said. i hope this makes sense to you.

[Dallasfan]

Chlamydia does not have a dormant phase in it`s lifecycle. A good percentage of people just have no symptoms. 20% of men and up to 40 % of women.