Chlamydia trachomatis

The bacterium Chlamydia trachomatis is among the oldest and most prevalent causes of infectious disease on earth.

Chlamydia is a curable sexually transmitted infection (STI); it is the most frequently reported bacterial STI in the United States. It is estimated that there are approximately 2.8 million new cases of chlamydia in the United States each year. Chlamydia cases frequently go undiagnosed and can cause serious problems in men and women, such as penile discharge and infertility respectively, as well as infections in newborn babies of infected mothers.



Chlamydia is caused by bacteria called Chlamydia trachomatis. The 15 varieties of C. trachomatis cause a range of diseases, from sexually transmitted infections (STIs) to a leading cause of infectious blindness, trachoma.



You can get a chlamydial infection during oral, vaginal, or anal sexual contact with an infected partner.



Chlamydia bacteria can live in vaginal fluid and in semen. About 70 percent of chlamydial infections have no symptoms, thereby naming it the "silent" disease. Symptoms usually appear within 1 to 3 weeks after you are infected. Those who do have symptoms may have an abnormal discharge (mucus or pus) from the vagina or penis or experience pain while urinating. These early symptoms may be very mild.


The bacterial infection may move inside your body if it is not treated.


  • In women, bacteria can infect the cervix and urinary tract. If the bacteria move into the fallopian tubes, they can cause pelvic inflammatory disease (PID).
  • In men, bacteria can infect the urinary tract and the epididymis, causing epididymitis (inflammation of the reproductive area near the testicles).

    PID and epididymitis are both very serious illnesses.


    C. trachomatis also can cause inflammation of your rectum and lining of your eye (conjunctivitis or "pink eye"). The bacteria also can infect your throat if you have oral sexual contact with an infected partner.



    Chlamydia is easily confused with gonorrhea because the symptoms of both diseases are similar and the diseases can occur at the same time.


    The most reliable ways to find out whether the infection is chlamydia are through laboratory tests.


  • A health care provider may collect a sample of fluid from the vagina or penis and send it to a laboratory that will look for the bacteria.
  • Another test looks for the bacteria in a urine sample and does not require a pelvic exam or swabbing of the penis. Results are usually available within 24 hours.


    If you are infected with C. trachomatis, your health care provider will probably give you a prescription for an antibiotic such as azithromycin (taken for one day) or doxycycline (taken for 7 days). Or, you might get a prescription for another antibiotic such as erythromycin or ofloxacin.


    Health care providers may treat pregnant women with azithromycin, erythromycin, or sometimes with amoxicillin. Penicillin, which health care providers often use to treat some other STIs, won't cure chlamydia.


    If you have chlamydia, you should


  • Take all your medicine, even after symptoms disappear, for the amount of time prescribed
  • Go to your health care provider again if your symptoms do not disappear within 1 to 2 weeks after finishing all your medicine
  • Not have sex until your treatment is completed and successful
  • Tell your sex partners that you have chlamydia so they can be tested and treated, if necessary

    These steps will help you avoid being reinfected with the bacteria. Repeated infections may increase the risks for reproductive complications.



    The surest way to avoid transmission of STIs is to abstain from sexual contact or be in a long-term mutually monogamous relationship with a partner who has been tested and is not infected.


    By using latex condoms correctly and consistently during vaginal or rectal sexual activity, you can reduce your risk of getting chlamydia and developing complications.


    Health care experts recommend all sexually active women 25 years of age and younger get chlamydia screening tests annually. They recommend an annual screening test for older women with risk factors for chlamydia (a new sex partner or many sex partners). In addition, all pregnant women should have a screening test for chlamydia.


    If you have genital symptoms like burning while urinating or have a discharge, you should stop having sexual intercourse and see your health care provider immediately.



    Each year up to 1 million women in the United States develop Pelvic Inflammatory Disease (PID), a serious infection of the reproductive organs. Twenty to forty percent of women with chlamydial infections that are not adequately treated may develop PID.


    PID can cause scarring of the fallopian tubes, which can block the tubes and prevent fertilization from taking place. Researchers estimate that 100,000 women each year become infertile because of PID.


    In other cases, scarring may interfere with the passage of the fertilized egg to the uterus during pregnancy. When this happens, the egg may attach itself to the fallopian tube. This is called ectopic or tubal pregnancy. This very serious condition can result in miscarriage and can cause death of the mother.


    In men, untreated chlamydia may lead to pain or swelling in the scrotal area. This is a sign of inflammation of the epididymis. Though complications in men are rare, infection could cause pain, fever, and sterility.


    Complications in newborns

    A baby who is exposed to C. trachomatis in the birth canal during delivery may develop an eye infection or pneumonia. Symptoms of an eye infection, called conjunctivitis or "pink eye," include discharge in the eye and swollen eyelids and usually develop within the first 10 days of life.


    Symptoms of pneumonia, including a cough that gets steadily worse and congestion, most often develop within 3 to 6 weeks of birth. Health care providers can treat both conditions successfully with antibiotics.


    Because of these risks to the newborn, many providers recommend that all pregnant women get tested for chlamydia as part of their prenatal care.