chlamydia (chlamydia trachomatis)risk of infection from oral sex giving oral sex to a partner with an infected penis can result in getting chlamydia in the throat. Giving oral sex to a partner with an infected vagina or urinary tract may result in getting chlamydia in the throat. Since chlamydia can be transmitted even if the penis or tongue does not completely enter the vagina, mouth or rectum, using latex condoms at the beginning of sexual contact until there is no longer skin contact is the best form of prevention. Several barrier methods can be used to reduce the risk of transmission of chlamydia during oral sex. men who have sex with men (msm) are also at risk for chlamydial infection since chlamydia can be transmitted by oral or anal sex. Among msm screened for rectal chlamydial infection, positivity has ranged from 3. 7 among msm screened for pharyngeal chlamydial infection, positivity has ranged from 0. Chlamydia transmission occurs during sexual contact with the genitals, anus or mouth of an infected person -- or from a mother to her baby during birth. It accounts for just under half of all new sti diagnoses in the uk, with around 200,000 cases recorded each year. Many people tend to presume that stis such as chlamydia can only be passed on through penetrative sex however, this is not the case.