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Chlamydia is a sexually transmitted infection, or STI, caused by the organism Chlamydia trachomatis. Sexually transmitted infection refers to any infection, whether bacterial, viral, or parasitic, transmitted from one person to another during sexual contact.

What is going on in the body?

The organism Chlamydia trachomatis causes chlamydia infection. It infects the cells and causes a number of changes. The organism is usually passed from one partner to another during sexual activity. Also, an infection can also be passed from an infected mother to her baby during birth.

• the urinary tract, cervix, or pelvis in women
• the urethra, the tube that carries urine from the bladder to the tip of the penis, in men
• the rectum, if anal sex is practiced
• the throat, if oral sex is practiced
• the eyes or lungs in newborns who are exposed to the mother's chlamydia infection during delivery

What are the signs and symptoms of the infection?

Many chlamydia infections do not cause any symptoms. For this reason, an individual may pass the infection on to a sexual partner without either partner being aware of it.

A chlamydia infection of the cervix in a female may include the following symptoms:

• vaginal discharge
• mild pain and discomfort when urinating
• abdominal distress, if the infection has spread to the uterus, tubes, or ovaries
• pain in the upper right of the abdomen, if the liver is involved

A chlamydia infection of the urethra in a male may include the following symptoms:

• watery or mucous-like discharge from the penis
• burning or pain with urination
• frequent urination

Chlamydia infections of the throat usually cause a sore throat. Chlamydia infections of the rectum can cause:

• rectal pain
• discharge from the rectum, which may be bloody
• frequent, painful urges to have a bowel movement

A newborn infected with chlamydia may have eye discharge from an eye infection or difficulty breathing because of pneumonia.

What are the causes and risks of the infection?

The organism that causes a chlamydia infection is usually passed from one partner to another during sexual activity. Any intimate contact of the genitals, mouth, rectal area, or the sharing of sexual toys can transmit the organism from one individual to another.

A person is at higher risk if he or she has more than one sexual partner.

A newborn baby is at risk of chlamydia infection if the mother has a chlamydia infection involving the birth canal.

What can be done to prevent the infection?

Use of a male or female condom can reduce, but not eliminate, the risk of acquiring chlamydia infection from an infected partner. Limiting sexual relations to a mutually faithful, lifelong relationship such as marriage is a more reliable way to prevent infection.

Any new partners should be asked about their sexual history and should be tested for sexually transmitted infections. Sexual contact should be postponed until the tests show no infection in the partner.

Finally, a screening for chlamydia can be done at the same time as a routine annual Pap smear and pelvic exam. Chlamydia screening in pregnant women can help stop the infection in newborns.

How is the infection diagnosed?

The healthcare professional may suspect a chlamydia infection after taking a medical history and performing an examination. The examiner may take a sample of material from the infected area to be checked in the laboratory for the organisms that cause the infection.

For a cervical infection, a culture of material from the surface of the cervix is taken during a pelvic examination. Culture specimens can also be taken from the urethra, rectum, throat, eyes, or other body sites.

What are the long-term effects of the infection?

It is important to treat chlamydia infections of the cervix in women to prevent scarring of the fallopian tubes, which connect the ovaries to the uterus. Severe or untreated chlamydia infections can cause the following serious complications:

• pelvic inflammatory disease (PID), an infection of the pelvic organs
• chronic pelvic pain
• pelvic adhesions, or bands of tissue that cause scarring
• infertility, or the inability to conceive a child
• ectopic pregnancy, in which the fertilized egg implants outside the uterus
• premature labor and premature delivery, if a woman is infected during pregnancy
• postpartum endometritis, an infection of the uterine lining that occurs after a woman has given birth
• proctitis (rectal infection)

Chlamydia infections in men can cause acute epididymitis, or an inflammation of a structure attached to the testes. Rectal chlamydia can cause narrowing of the rectum or ulcers in the rectum.

Chlamydia infections of the newborn can cause visual impairment, respiratory problems, and death.

What are the risks to others?

Chlamydia infections are highly contagious and can be passed through sexual intercourse and other intimate contact. A woman who is pregnant can pass the chlamydia infection to her baby during delivery. The baby may then develop an eye infection or pneumonia.

What are the treatments for the infection?

Taking antibiotics usually cures the infection. Normal healing may still leave some scar tissue. Sexual partners should also be treated. Sometimes a combination of antibiotics is used for 7 to 10 days.

Antibiotics used to treat chlamydial infections include:

• azithromycin (i.e., Zithromax, Zmax)
• doxycycline (i.e., Adoxa, Doryx, Oracea, Periostat, Vibramycin),
• ofloxacin (i.e., Floxin),
• levofloxacin (i.e., Levaquin),
• extended spectrum penicillins, and
• erythromycin base or erythromycin ethylsuccinate (i.e., EES).

For severe infections that spread to the abdomen, the antibiotics need to be given intravenously in the hospital. Like most sexually transmitted infections, having the infection once does not give an individual enough immunity to keep him or her from getting it again. Anyone can be infected repeatedly.

What are the side effects of the treatments?

Antibiotics may cause stomach upset, rash, or allergic reactions.

What happens after treatment for the infection?

Antibiotic treatment usually works, but there may still be scarring of the woman's reproductive organs. If the person does not finish taking the entire course of antibiotics, the infection may persist. Reinfection may also occur unless all sexual partners are treated.

How is the infection monitored?

After a course of antibiotics has been taken successfully, the healthcare professional may repeat the culture of material from the infected area. If the test is positive, it usually means reinfection has occurred. This is particularly likely if a sexual partner has not been treated or did not complete treatment.

Screening for chlamydia is frequently carried out as part of a woman's annual physical examination, especially for teenaged and young adult women seeking birth control or being treated for other STIs. When a man or woman is diagnosed with gonorrhea, public health officials recommend that he or she be treated for possible chlamydia infection at the same time.

Any new or worsening symptoms should be reported to the healthcare professional.