Chlamydia trachomatis is an obligate, intracellular bacterium with 15 immunotypes, as follows: A-C cause trachoma (chronic conjunctivitis endemic in Africa and Asia); D-K, genital tract infections; and L1-L3, lymphogranuloma venereum (associated with genital ulcer disease in tropical countries). Chlamydia is the most commonly reported bacterial sexually transmitted disease (STD) in the United States and is one of the leading causes of infertility in women.
The US Preventive Services Task Force recommends the following1,2 : (1) screening for chlamydial infection in all sexually active nonpregnant young women aged 24 years or younger and for older nonpregnant women who are at increased risk; (2) screening for chlamydial infection in all pregnant women aged 24 years or younger and in older pregnant women who are at increased risk; and (3) not routinely screening for chlamydial infection in women aged 25 years or older, regardless of whether they are pregnant, if they are not at increased risk. Also see these guidelines at the National Guideline Clearinghouse.
Routine chlamydia screening of sexually active young women is recommended to prevent consequences of untreated chlamydial infection (eg, pelvic inflammatory disease, infertility, ectopic pregnancy, chronic pelvic pain). Fewer than half of young, sexually active females in the United States are screened for chlamydia, reports MMWR. Nationally, the annual screening rate increased from 25.3% in 2000 to 43.6% in 2006, and then decreased slightly to 41.6% in 2007.3
Infection of the genital tract is the most common clinical presentation. The incubation period is 1-3 weeks. Approximately 50% of infected males and 80% of infected females are asymptomatic, but infection may cause a mucopurulent cervicitis in females and urethritis in males. Ascending infection can result in pelvic inflammatory disease (PID) in women and is the most common cause of epididymitis in men younger than 35 years. Of women with PID, 5-10% develop perihepatitis (ie, Fitz-Hugh and Curtis syndrome).
Although patients with any sexually transmitted disease (STD) are at increased risk of co-infection with another STD, co-infection of chlamydia and gonorrhea is most common. Forty percent of women and 20% of men with chlamydial infection are co-infected with gonorrhea. Patients with chlamydia also have a higher frequency of Reiter syndrome (ie, urethritis, conjunctivitis, reactive arthritis) than the general population.
Lymphogranuloma venereum is rare in the US but is responsible for 10% of genital ulcer disease in tropical countries. Localized inguinal adenopathy and ulceration develop 2-12 weeks after exposure. Proctitis, rectal strictures, and lymphatic obstruction with secondary elephantiasis can occur in untreated disease.
Chlamydia is transmitted via the birth canal of an infected mother, and neonates exposed to chlamydia at birth may develop conjunctivitis 5-13 days later. C trachomatis immunotypes A-C, which are endemic in Africa, cause a chronic conjunctivitis.
C trachomatis is one of the most common causes of pneumonia in the newborn. Chlamydial infection develops in 60% of neonates born vaginally to infected mothers.
Approximately 4 million cases of chlamydial infection are reported per year in the United States, with an overall prevalence of 5%. At-risk groups (eg, sexually active adolescent girls) have a higher prevalence, with an incidence of 10%. A prevalence of chlamydia as high as 14% has been reported in African American females aged 18-26 years and 17% among females with a history of gonorrhea or chlamydia in the previous 12 months. In addition, approximately 100,000 neonates are exposed to chlamydia annually.
Chlamydial infection is one of the leading causes of infertility in women. Other long-term problems caused by chlamydial infection include PID, chronic pelvic pain, and perihepatitis. Women with a chlamydial infection (especially serotype G) are at an increased risk of developing cervical cancer; risk is as high as 6.5 times greater than in women without infection. Untreated neonatal conjunctivitis can result in blindness.
The disease is more common among minorities, lower socioeconomic groups, and people living in urban areas than in the general population.
Women are more likely to be asymptomatic than men (80% vs 50%). However, women are more likely to develop long-term complications (eg, PID, infertility).
Prevalence rates are highest in adolescent girls (>10%).
May have a history of STDs
Yellow mucopurulent discharge from the urethra
Intermenstrual or postcoital bleeding
Lower abdominal pain
Fever (in PID)
No symptoms in 80%
Unilateral pain and swelling of the scrotum
Asymptomatic in 50%
Mucopurulent discharge from eyes
Bilateral involvement of the eyes
Men may have any, all, or none of the following:
Mucopurulent urethral discharge
Unilateral epididymal tenderness and swelling
Mucopurulent rectal discharge (from anal intercourse)
Women may have any, all, or none of the following:
Mucopurulent cervical or vaginal discharge
Cervical motion tenderness
Lower abdominal tenderness
Upper right quadrant abdominal tenderness (Fitz-Hugh and Curtis syndrome)
Mucopurulent rectal discharge (from anal intercourse)
Neonates – Bilateral purulent conjunctivitis
Localized inguinal adenopathy or buboes
“Groove sign” – Separation of inguinal and femoral lymph nodes by the inguinal ligament (15-20% of patients)
Chlamydial transmission usually is caused by sexual contact through oral, anal, or vaginal intercourse. The incubation period is 1-3 weeks.
Neonatal infection may occur secondary to passage through the birth canal of an infected mother. Two thirds of infants born to mothers with chlamydia develop an infection.
Specific risk factors include multiple sexual partners, a new sexual partner, lack of barrier contraceptive, and co-infection with another STD.