Chlamydial infections include sexually transmitted diseases of the urethra and cervix that are caused by the bacteria Chlamydia trachomatis. Less commonly, other bacteria, such as Ureaplasma and mycoplasmas, cause infection of the urethra.

• Symptoms include a discharge from the penis or vagina and painful or more frequent urination.
• If unnoticed or untreated in women, these infections can result in infertility, miscarriage, and an increased risk of a mislocated pregnancy.
• DNA tests of a sample of the discharge or of urine can detect chlamydial infection.
• Antibiotics can cure the infection, and sex partners should be treated at the same time.

Several bacteria can cause diseases that resemble gonorrhea. These bacteria include Chlamydia trachomatis, Trichomonas vaginalis, Ureaplasma, and several types of mycoplasmas. Laboratories can identify chlamydiae but have difficulty identifying the other bacteria. So the infections caused by these other bacteria are called nongonococcal, nonchlamydial infections, usually of the urethra (urethritis).

Chlamydial infection is the most commonly reported sexually transmitted disease (STD). In the United States, over 1 million cases were reported in 2006. Because the infection frequently causes no symptoms, the number of infected people may be 4 times higher. In men, chlamydiae cause about half of the urethral infections not caused by gonorrhea. Most of the remaining urethral infections in men are probably caused by Ureaplasma urealyticum or mycoplasmas. In women, chlamydiae account for virtually all of the cervical infections (cervicitis) that produce pus and that are not caused by gonorrhea. Sometimes both sexes have gonorrhea and chlamydial infection at the same time.

Symptoms

In men, symptoms of chlamydial urethritis start 7 to 28 days after the infection is acquired during intercourse. Typically, men feel a mild burning sensation in their urethra during urination and may have a clear or cloudy discharge from the penis. The discharge is usually less thick than the discharge in gonorrhea. The discharge may be small, and symptoms mild. However, early in the morning, the opening of the penis is often red and stuck together with dried secretions. Occasionally, the infection begins more dramatically—with a frequent urge to urinate, painful urination, and a discharge of pus from the urethra.

Many women with chlamydial cervicitis have few or no symptoms. But some have frequent urges to urinate, painful urination, and secretions of yellow mucus and pus from the vagina.

Complications: If the infection spreads up women's reproductive tract, it may infect the tubes that connect the ovaries to the uterus (fallopian tubes). This infection, called salpingitis or pelvic inflammatory disease, causes severe lower abdominal pain. In some women, the lining of the abdominal cavity (peritoneum) becomes inflamed. This inflammation, called peritonitis, causes more severe pain in the lower abdomen and sometimes in the area around the liver, in the right upper abdomen.

If the anus is infected, people may have rectal pain or tenderness and a yellow discharge of pus and mucus from the rectum.

Chlamydiae may be transferred to the eye, causing infection of the conjunctiva (conjunctivitis).

Chlamydial genital infections occasionally cause a joint inflammation called reactive arthritis (previously called Reiter's syndrome—see Joint Disorders: Reactive Arthritis). Reactive arthritis typically affects several joints at once. The lower limbs are affected most often. The inflammation seems to be an immune reaction to the genital infection rather than spread of the infection to the joints. Symptoms typically begin 1 to 3 weeks after the initial chlamydial infection.

If chlamydial urethritis is not treated, symptoms usually disappear in 4 to 6 weeks. However, if untreated, a chlamydial infection can cause complications, especially in women who have been infected a long time. Complications include chronic abdominal pain and scarring of the fallopian tubes. The scarring can cause infertility and a mislocated (ectopic) pregnancy (see Complications of Pregnancy: Ectopic Pregnancy).

In men, chlamydial infections may cause epididymitis, which causes painful swelling of the scrotum on one or both sides (see Penile and Testicular Disorders: Epididymitis and Epididymo-orchitis). Other bacteria from the intestine also contribute to these complications probably by infecting areas that have been damaged by chlamydiae.

Did You Know... Chlamydial infections are the most common sexually transmitted disease. Because chlamydial infection and gonorrhea often occur together, people with one of them are routinely treated for both.

Diagnosis

Doctors suspect these infections based on symptoms, such as a discharge from the penis or cervix. In most cases, doctors diagnose chlamydial infections by doing tests that detect the bacteria's unique genetic material (DNA or RNA). Usually, a sample of the discharge from the penis or cervix is used. For some types of these tests, a urine sample can be used. Thus, people can avoid the discomfort of having a swab inserted into the penis or having a pelvic examination to obtain a sample.

Gonorrhea, which is often also present, can be diagnosed using the same sample. Specific tests for genital infections with Ureaplasma and mycoplasmas are not usually done. These infections are sometimes diagnosed in people with characteristic symptoms after gonorrhea and chlamydial infections are ruled out.

Screening: Because chlamydial infection is so common and because many infected women have no symptoms, these tests are recommended for sexually active women aged 15 to 25 to screen for STDs.

Possible Complications of Chlamydial and Ureaplasmal Infections
In men Infection of the epididymis Narrowing (stricture) of the urethra In women Infection of the fallopian tubes (salpingitis) Infection of the membrane that lines the abdominal cavity (peritonitis) Infection of the surface of the liver In men and women Infection of the membrane that covers part of the eye (conjunctivitis) In newborns Conjunctivitis Pneumonia

Treatment

Chlamydial, ureaplasmal, and mycoplasmal infections are treated with a single dose of azithromycin or with doxycycline or levofloxacin taken by mouth for 7 days. At the same time, an antibiotic such as ceftriaxone, injected into a muscle, is given to treat gonorrhea because the symptoms of the two infections are similar and because many people have both infections at the same time. Pregnant women are given azithromycin instead of tetracycline or doxycycline, which must be avoided during pregnancy. If symptoms persist or return, treatment is repeated for a longer period.

Infected people should abstain from sexual intercourse until they have completed treatment to avoid infecting their sex partners. Sex partners should be treated simultaneously if possible and should abstain from sexual intercourse until they complete treatment. The risk of another chlamydial infection or another STD within 3 to 4 months is high enough that people should be screened again at that time.

Last full review/revision October 2008 by J. Allen McCutchan, MD, MSc