I am positive for NSU, but girlfriend tested negative?

Patient: I live in the UK, recently got treated for NSU non-specific urethritis And i had sexual contact with 2 girls, one went to the docs and received treatment and the other went to the same clinic as i did but was tested negative. We only had sex once and she got tested more than 2 weeks after. Could the test have been wrong or is there a chance i did not pass it on to her?

Doctor: Non specific urethritis may be caused by multiple organisms (other than the common STD infections), that are less common and so may not have been tested for by the lab, thus reporting a negative test result. A history of exposure, clinical examination and symptoms provide an important clue to the diagnosis of this condition. There could also be a possibility that your girlfriend may not have developed any positive symptoms to signify infection. If you carried the infection at the time you had sex with your girlfriend, it is likely for her be infected as well.