Chlamydia

ANATOMY OR SYSTEM AFFECTED: Eyes, genitals, lungs, lymphatic system, reproductive system, urinary system

DEFINITION: One of the most common sexually transmitted bacterial diseases, which primarily infects the reproductive tract and is caused by the bacterium Chlamydia trachomatis.

CAUSES: Bacterial infection of mucosa (genital tract, urinary tract, anorectal tract, eyes, throat) through sexual transmission or childbirth

SYMPTOMS: Often none, but may include urinary discomfort, lower abdominal pain, abnormal discharge from vagina or urethra, complications such as pelvic inflammatory disease (PID) and infertility; in infants, eye infection, visual impairment, blindness, respiratory tract infection

DURATION: Chronic until treated

TREATMENTS: Antibiotics (doxycycline, azithromycin, erythromycin, ofloxacin)

Causes and Symptoms

Chlamydia is one of the most common sexually transmitted diseases, with a prevalence of about 0.1 to 12.1 percent in sexually active men and women worldwide. Prevlance varies widely by country. Chlamydia is a bacterial diseasecaused by Chlamydia trachomatis, which infects cells on mucosal surfaces, such as the genital tract, urinary tract, anorectal tract, eyes, and throat. These infections cause inflammation of the cervix, urethra, prostate, or epididymis. In women, symptoms may include urinary discomfort, painful intercourse, lower abdominal pain, pelvic pain, and abnormal vaginal discharge. Women are commonly asymptomatic in the early stages of the disease. In men, symptoms may involve urinary discomfort, scrotal pain or swelling, and unusual discharge from the urethra. Men may also be asymptomatic in early stages of the disease.

Most cases of chlamydia are asymptomatic, with 45 to 95 percent of cases having no symptoms. Because most patients with chlamydia are unaware they are infected, the incidence of chlamydia has risen significantly throughout the years in the United States, with 1.81 million cases in 2018. While this number dropped to 1.58 million in 2020, it rose to 1.64 million in 2021 and remained about the same in 2022, the latest year for which statistics are available. Safe sex practices are essential to preventing the spread of chlamydia and other STDs. Most patients are diagnosed based on screening procedures. Asymptomatic patients are able to infect others and can suffer serious consequences of chlamydia infection, such as pelvic inflammatory disease (PID) and infertility. PID occurs when chlamydia infection ascends the female reproductive tract to involve the uterus, Fallopian tubes, and pelvic cavity. This infection of the upper reproductive tract can lead to scarring of these organs and puts the patient at increased risk of infertility and ectopic pregnancy.

In rare cases, chlamydia can travel to regional lymph nodes and cause abscesses, a condition termed lymphogranuloma venereum. This condition is commonly accompanied by systemic symptoms such as fever, chills, and muscle and joint aches.

An infant may contract chlamydia as it passes through the birth canal of an infected mother during childbirth. The disease can lead to eye infection that results in visual impairment and blindness, as well as infection of the respiratory tract.

Treatment and Therapy

A patient receives antibiotic therapy if laboratory tests indicate infection with C. trachomatis. Uncomplicated chlamydia infection can be treated effectively with antibiotics such as azithromycin, doxycycline, erythromycin, or ofloxacin. A patient with risk factors for STDs or symptoms of the disease may be treated presumptively with antibiotic therapy, even before the results of laboratory tests for chlamydia return. People at risk for contracting STDs engage in high-risk sexual behaviors, including multiple sexual partners, frequent changes in sexual partners, and inconsistent condom use among persons not in a mutually monogamous relationship.

Because chlamydia is associated with other STDs, such as gonorrhea, human immunodeficiency virus (HIV), syphilis, and hepatitis B and C, the patient should be advised to undergo testing for these diseases as well. Approximately 35 to 50 percent of patients with gonorrhea also have chlamydia, so an antibiotic against chlamydia is given along with an antibiotic for gonorrhea, unless laboratory tests have declared the patient free of chlamydia. If chlamydia and gonorrhea are treated early, complications such as PID or infertility can be avoided.

In addition to antibiotics, a key component of chlamydia treatment involves counseling in the prevention of STDs. To minimize future exposure to chlamydia and other STDs, patients are encouraged to use barrier methods such as condoms during intercourse and to avoid high-risk sexual behaviors.

Another key component to the treatment of chlamydia and other STDs is contact tracing, which occurs once the infection is confirmed with laboratory testing. With the cooperation of the patient, all sexual partners of the patient are notified regarding their exposure to disease. Partners are encouraged to seek medical attention, even if they have no symptoms themselves, in order to prevent reinfection of the patient during subsequent sexual encounters or further spread of the disease to other sexual partners.

In the United States, erythromycin eyedrops are given prophylactically to all newborns to prevent eye infections with chlamydia that could lead to visual impairment.

Perspective and Prospects

Diseases caused by C. trachomatis have been described as early as ancient Egyptian times. It was not until 1907, however, that the bacterium was actually identified, and there was some controversy about whether it was a true bacterium because it requires host cells to live (obligate intracellular parasite). The organism favors cells that are more available on the cervix of young (versus older) women, which is partly why rates of chlamydia are so much higher in the young. In the 1960s, a clinically useful diagnostic test was developed that allowed screening of a large number of specimens within a few days. The development of a relatively easy test for chlamydia enabled clinicians to screen a large number of asymptomatic but at-risk patients (such as those under age twenty-five or those with multiple sexual partners).

A promising area of research is the search for a vaccine to C. trachomatis. This research focuses on identifying antigens on the bacterium that are important for its function, such as proteins responsible for bacterial attachment to or uptake into cells. The premise is to use these proteins to generate an immune response in patients so that when patients are exposed to chlamydia, their immune systems are prepared to respond against it.

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