Chlamydia infection overview

# Overview
Chlamydia is a common sexually transmitted disease (STD) caused by the gram negative bacterium Chlamydia trachomatis.  Chlamydia is the most frequently reported bacterial sexually transmitted infection in the United States and is a major infectious cause of human eye and genital disease. Chlamydia infection must be differentiated from other genital tract infections, such as gonorrhea infection, bacterial vaginosis, vaginal candidiasis, infection with Trichomonas vaginalis, and mycoplasma infection. Almost two-thirds of new chlamydia infections occur among youth aged 15-24 years. Females are more commonly affected with chlamydia infection than males. The female to male ratio is approximately 1.52 to 1. Common risk factors in the development of chlamydia infection include unprotected sexual activity, multiple sexual partners, age, men who have sex with men, and low socioeconomic status. According to the 2015 Sexually Transmitted Diseases Treatment Guidelines released by the CDC, screening for chlamydia is recommended for sexually active individuals under 25 years of age, women over 25 who are at increased risk, all pregnant women under 25 years, pregnant women over 25 who are at increased risk, men who have sex with men, and individuals with HIV. If left untreated, chlamydia can cause pelvic inflammatory disease in females and epididymitis and orchitis in males. Common complications of chlamydia among women include cervicitis, infertility, ectopic pregnancy, and chronic pelvic pain.  Complications of chlamydia in men include proctitis, epididymitis, and sterility. Prognosis of chlamydia is generally good with adequate treatment. Common symptoms of chlamydia infection among women include abnormal vaginal bleeding or discharge, abdominal pain, painful sexual intercourse, painful urination, and urinary urgency. Symptoms of chlamydia infection among men include penile discharge and pruritus, testicular pain or swelling, and pain during urination. Physical examination of women with chlamydia infection is usually remarkable for a cloudy, yellow mucoid cervical discharge; a friable appearance of the cervix; and cervical motion tenderness. Common physical examination findings of chlamydia infection among men include a clear or white urethral discharge, testicular tenderness, and testicular swelling. Transvaginal ultrasound, pelvic MRI, and laboratory nucleic acid amplification tests (NAAT) may be used in the diagnosis of chlamydia infection. The mainstay of therapy for chlamydia is antimicrobial therapy with doxycycline. Effective measures for the primary prevention of chlamydia infection include practicing abstinence, avoiding high-risk sexual behaviors such as unprotected sex or multiple sexual partners, and using latex condoms. Secondary prevention of chlamydia infection includes early detection, treatment of sexual partners, and treatment of other sexually transmitted infections (such as gonorrhea).

# Historical Perspective
Chlamydia trachomatis was first discovered in 1907 by Halberstaedter and von Prowazek. The inclusion bodies of Chlamydia trachomatis were first described in 1942.

# Pathophysiology
C. trachomatis is naturally found living only inside human cells.  Chlamydia can be transmitted during vaginal, anal, or oral sex, and can be passed from an infected mother to her baby during vaginal childbirth.

# Causes
Chlamydia is a common sexually transmitted infection (STI) caused by the gram-negative bacterium Chlamydia trachomatis.

# Differentiating Chlamydia infection from other diseases
Chlamydia must be differentiated from other genital tract infections such as gonorrhea infection, bacterial vaginosis, vaginal candidiasis, infection with Trichomonas vaginalis, and mycoplasma infection.

# Epidemiology and Demographics
In 2014, the incidence of chlamydia was estimated to be 439 cases per 100,000 individuals in the United States. The incidence of chlamydia in women has increased greatly between 1987 and 2003 from 79 to 467 cases per 100,000 individuals. Almost two-thirds of new chlamydia infections occur among young adults aged 15-24 years. It is estimated that 1 in 20 sexually active young women aged 14-24 years has chlamydia. Females are more commonly affected with chlamydia infection than males. The female to male ratio is approximately 1.52 to 1. The prevalence of chlamydia among non-Hispanic African Americans is 6.7 times the prevalence among non-Hispanic Whites.

# Risk Factors
Common risk factors in the development of chlamydia infection include unprotected sexual activity, multiple sexual partners, age, men who have sex with men, and low socio-economic status.

# Screening
According to the 2015 Sexually Transmitted Diseases Treatment Guidelines by the CDC, screening for chlamydia is recommended for sexually active under 25 years, women over 25 who are at increased risk, all pregnant women under 25 years, pregnant women over 25 who are at increased risk, men who have sex with men, and individuals with HIV.

# Natural History, Complications and Prognosis
If left untreated, chlamydia can cause pelvic inflammatory disease in women and epididymitis and orchitis in males. Common complications of chlamydia among women include cervicitis, infertility, ectopic pregnancy, and chronic pelvic pain.  Complications of chlamydia in men include proctitis, epididymitis, and sterility. Other complications of chlamydia include reactive arthritis. Prognosis of chlamydia is generally good with adequate treatment.

# Diagnosis

## History and Symptoms
It is crucial to collect a detailed and thorough sexual history from the patient. Specific areas of focus when obtaining a history include number and type of sexual partners (new, casual, or regular), contraception use, and previous history of chlamydia infection or other sexually transmitted diseases. The majority of women with chlamydia infection are asymptomatic or present with minimal symptoms. Common symptoms of chlamydia infection among women include abnormal vaginal bleeding or discharge, abdominal pain, painful sexual intercourse, painful urination, and urinary urgency. Symptoms of chlamydia infection among men include penile discharge and pruritus, testicular pain or swelling, and pain during urination.

## Physical Examination
Patients with chlamydia infection usually appear to be in good health. A fever may be present. Physical examination of women with chlamydia infection is usually remarkable for a cloudy, yellow mucoid cervical discharge; a friable appearance of the cervix; and cervical motion tenderness. Common physical examination findings of chlamydia infection among men include a clear or white urethral discharge, testicular tenderness, and testicular swelling.

## Laboratory Findings
Laboratory tests used in the diagnosis of chlamydia infection include nucleic acid amplification tests (NAAT) such as polymerase chain reaction (PCR), transcription mediated amplification (TMA), and the DNA strand displacement assay (SDA). NAAT for chlamydia infection may be performed on swab specimens sampled from the cervix (women) or urethra (men), on self-collected vaginal swabs, or on voided urine.

## Ultrasound
Transvaginal ultrasound may be helpful in the diagnosis of chlamydia infection when pelvic inflammatory disease has occurred. Findings on ultrasound suggestive of pelvic inflammatory disease include thickened/dilated fallopian tubes, incomplete septa in the fallopian tube, increased vascularity around the fallopian tubes, and positive cogwheel sign (thickened loops of fallopian tubes).

## Other Imaging Findings
Other imaging studies for chlamydia infection include pelvic MRI, which demonstrates an ill-defined adnexal mass containing fluid with various signal intensities.

# Treatment

## Medical Therapy
The mainstay of therapy for chlamydia is antimicrobial therapy with doxycycline.  Recent sex partners (i.e., individuals having sexual contact with the patient within the 60 days preceding onset of symptoms or chlamydia diagnosis) should also be referred for evaluation, testing, and treatment.

## Primary Prevention
Effective measures for the primary prevention of chlamydia infection include practicing abstinence, avoidance of high-risk sexual behaviors such as unprotected sex or multiple sexual partners, and use of latex condoms.

## Secondary Prevention
Secondary prevention of chlamydia infection includes early detection, treatment of sexual partners, and treatment of other sexually transmitted infections (such as gonorrhea).