Chlamydia: Diagnosing the hidden STD

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After infection, Chlamydia (blue) replicate in a large vesicle inside the cell.
After infection, Chlamydia (blue) replicate in a large vesicle inside the cell.

Chlamydia is the most frequently reported and most common bacterial sexually transmitted disease (STD) in the United States, with more than 2.8 million cases occurring annually, mainly among those aged 15-24.1 Most chlamydial infections are asymptomatic, with up to 75% of females and 50% of males exhibiting no symptoms. As such, most cases remain undiagnosed. 2,3

While the national rate of reported cases increased by 5.9% between 2003 and 2004, this likely reflects the increased sensitivity and specificity of testing, as well as expanded screening efforts, rather than an actual increase in incidence. Women, especially young women, are disproportionately affected, with case rates reported for females 3.3 times higher than those for their male counterparts (Figure 1). It is important to note, however, that females are far more likely to be screened than males.4

The need for interventions to increase screening, improve quality of care, and reduce the estimated $2.4 billion spent annually in direct medical costs is evident.5 Only 13% of infections reported to the CDC are diagnosed at STD clinics,6,7 so for adolescents and young adults, interventions are especially important in private practices. Two thirds of women of reproductive age in the United States are commercially insured.

Organism

Chlamydia is the result of infection with the bacterium Chlamydia trachomatis. Its name is derived from the Greek word chlamys, meaning “cloak,” which describes how the bacteria cloak themselves around the infected cell's nucleus.

An obligate intracellular bacterium, C. trachomatis was thought to be a virus until the mid-1960s, when it was grown on cell culture. Because symptoms resembled other diseases, chlamydia was not recognized as an STD until the mid-1980s. The infectious particles, called “elementary bodies,” are 0.3 microns in diameter and “sporelike,” which helps ensure the organism's survival. The elementary bodies enter the host epithelial cell and condense to form metabolically active reticulate bodies. They multiply quickly and release their progeny in 48-72 hours.

There are 15 different serotypes of C. trachomatis that cause four major diseases in humans: endemic trachoma (serotypes A, B, Ba, and C), genital tract infection and inclusion conjunctivitis (serotypes D through K), and lymphogranuloma venereum (LGV) (serotypes L1, L2, and L3).8 Endemic trachoma is a leading cause of worldwide blindness. 

Infected secretions are transmitted through oral, vaginal, penile and/or anal sexual contact. This article will focus on genital tract infections, which include urethritis, epididymitis, cervicitis, endometritis, salpingitis, pelvic inflammatory disease (PID), and perihepatitis.

Sequelae

Because most patients with chlamydia are asymptomatic and unaware that they are infected, the chance of transmitting the bacteria to their sexual partners is high. This lack of awareness also delays screening and treatment, ultimately leading to increased risk of developing complications. Some women with seemingly uncomplicated cervical infection have already developed subclinical upper-reproductive-tract disease.9

A small percentage of women (20%-30%) may develop symptoms, such as vaginal discharge, dysuria, irritation around the vaginal area, bleeding after intercourse or abnormal vaginal bleeding, and/or lower abdominal pain. Half of all male patients report symptoms, including dysuria, white or yellow discharge, and tingling and/or itching in the penis.10

Women, however, are much more likely to suffer deleterious consequences from chlamydial infection than men. As many as 10%-40% of untreated genital infections may ascend and result in PID, which can cause permanent damage to the uterus, fallopian tubes, and surrounding tissue, leading to adverse reproductive and health consequences. If a woman develops PID, she has an 18% chance of developing chronic pelvic pain, a 20% chance of being infertile, and a 9% chance of having a future ectopic pregnancy.11 Chlamydia remains the most common cause of tubal infertility in this country. A recent study conducted in a managed-care setting suggests that chlamydia screening and treatment can cut in half the incidence of PID.12

In women of childbearing age, infection or previous infection can lead to ectopic pregnancy. Premature rupture of the membranes and preterm birth have also been reported.11 Spontaneous abortion related to infection during the first trimester remains controversial.

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