Chlamydia

Overview

Chlamydia is one of the most common sexually transmitted infections (STIs) worldwide, caused by the bacterium Chlamydia trachomatis. According to the Centers for Disease Control and Prevention (CDC), there are approximately 4 million new cases annually in the United States alone. What makes chlamydia particularly concerning is that it's often called the "silent infection" because 70-90% of infected individuals experience no symptoms, allowing it to spread unknowingly and cause complications if left untreated.

This bacterial infection primarily affects the genitourinary tract but can also infect the rectum, throat, and eyes. In women, untreated chlamydia can ascend from the cervix to the upper reproductive tract, causing pelvic inflammatory disease (PID), which may lead to chronic pelvic pain, ectopic pregnancy, and infertility. In men, it can cause urethritis and epididymitis, potentially affecting fertility. Pregnant women with chlamydia can transmit the infection to their babies during childbirth, potentially causing eye infections or pneumonia in newborns.

The good news is that chlamydia is easily curable with antibiotics when detected early. Regular screening is recommended for sexually active individuals, particularly those under 25 years old or those with risk factors. The infection affects people of all ages and backgrounds, but it's most common among young adults aged 15-24. Understanding chlamydia's transmission, symptoms, and prevention is crucial for maintaining sexual health and preventing long-term complications.

Symptoms

Chlamydia is notorious for being asymptomatic in the majority of cases. When symptoms do occur, they typically appear 1-3 weeks after exposure, though some people may not develop symptoms for months or until complications arise.

Symptoms in Women

Women are more likely than men to be asymptomatic, with up to 90% showing no initial symptoms:

• Vaginal discharge - Abnormal discharge that may be yellowish or have a strong odor
• Pelvic pain - Discomfort in the lower pelvis, may indicate PID
• Lower abdominal pain - Often a sign of infection spreading
• Vaginal itching - Irritation around the genital area
• Vaginal pain - Discomfort during intercourse (dyspareunia)
• Burning sensation during urination
• Bleeding between menstrual periods
• Bleeding after sexual intercourse
• Heavier menstrual periods

Symptoms in Men

Men are more likely to experience symptoms than women, though many still remain asymptomatic:

• Discharge from the penis - Clear, white, or yellowish
• Burning sensation when urinating
• Pain and swelling in one or both testicles
• Itching or irritation inside the penis
• Pain during ejaculation
• Rectal pain, discharge, or bleeding (if rectally infected)

Symptoms in Other Body Sites

Rectal Chlamydia

• Rectal pain
• Discharge from the rectum
• Rectal bleeding
• Often asymptomatic

Pharyngeal (Throat) Chlamydia

• Usually asymptomatic
• Possible sore throat
• Rarely causes symptoms

Ocular Chlamydia

• Eye redness and irritation
• Discharge from the eye
• Sensation of having something in the eye
• Light sensitivity

Symptoms of Complications

Pelvic Inflammatory Disease (PID) in Women

• Sharp abdominal pain - Severe pain indicating upper tract infection
• Fever and chills
• Nausea and vomiting
• Painful intercourse
• Irregular menstrual bleeding

Epididymitis in Men

• Testicular pain and swelling
• Fever
• Scrotal warmth and redness
• Pain during urination or ejaculation

Reactive Arthritis (Formerly Reiter's Syndrome)

• Joint pain and swelling
• Eye inflammation
• Urinary symptoms
• Skin rashes

Causes

Chlamydia is caused by the bacterium Chlamydia trachomatis, an obligate intracellular pathogen that can only survive and replicate inside human cells. Understanding how this bacteria spreads and infects is crucial for prevention and treatment.

The Causative Agent

Chlamydia trachomatis is unique among bacteria because:

• It cannot produce its own energy and must parasitize host cells
• It has a complex life cycle involving two forms: elementary bodies (infectious) and reticulate bodies (replicative)
• Different serovars cause different conditions (genital infections, trachoma, lymphogranuloma venereum)
• It can evade the immune system, leading to chronic infections

Transmission Methods

Sexual Transmission

The primary mode of transmission is through sexual contact:

• Vaginal sex: Most common route of transmission
• Anal sex: Can cause rectal infections
• Oral sex: Can cause pharyngeal infections or transmit genital infections
• Genital-to-genital contact: Even without penetration
• Sharing sex toys: If not properly cleaned between users

Vertical Transmission

Mother-to-child transmission during childbirth:

• Occurs in 50-60% of infants born to infected mothers
• Can cause neonatal conjunctivitis (eye infection)
• May lead to pneumonia in newborns
• Not transmitted through breastfeeding

Other Transmission Routes

• Auto-inoculation: Transferring infection from genitals to eyes with contaminated hands
• Contaminated surfaces: Rare but possible in moist environments
• Not transmitted through: Toilet seats, swimming pools, hot tubs, sharing utensils, or casual contact

Infection Process

Once transmitted, the infection process involves:

1. Attachment: Elementary bodies attach to epithelial cells
2. Entry: Bacteria are taken into cells via endocytosis
3. Replication: Transform into reticulate bodies and multiply
4. Release: New elementary bodies are released to infect other cells
5. Inflammation: Host immune response causes symptoms and tissue damage

Factors Affecting Transmission

• Viral load: Higher bacterial loads increase transmission risk
• Mucosal integrity: Breaks in mucous membranes facilitate infection
• Concurrent infections: Other STIs increase susceptibility
• Immune status: Weakened immunity increases risk
• Sexual practices: Certain practices may increase exposure risk

Risk Factors

Understanding risk factors for chlamydia helps identify individuals who should be regularly screened and counseled about prevention strategies.

Demographic Risk Factors

• Age: Highest risk in those under 25 years old
  • Adolescents and young adults have highest infection rates
  • Cervical ectopy in younger women increases susceptibility
  • Risk behaviors more common in younger age groups
• Gender: Women have higher complication risks
  • Anatomical factors make ascending infection easier
  • More likely to be asymptomatic
  • Greater long-term reproductive health consequences
• Sexual orientation: Men who have sex with men (MSM) have increased risk for rectal and pharyngeal infections

Behavioral Risk Factors

• Multiple sexual partners: Risk increases with number of partners
• New sexual partner: Within the last 60 days
• Inconsistent condom use: Or no barrier protection
• Previous STI history: Indicates risk behaviors and possible reinfection
• Partner with STI: Known infected partner or partner with symptoms
• Commercial sex work: Both workers and clients
• Substance use: Associated with risky sexual behaviors

Social and Economic Factors

• Limited access to healthcare: Reduces screening and treatment
• Low socioeconomic status: Barriers to prevention and care
• Incarceration history: Higher prevalence in correctional facilities
• Living in high-prevalence areas: Geographic clustering of infections
• Limited sex education: Lack of knowledge about prevention

Clinical Risk Factors

• Cervical ectopy: Common in adolescents and OCP users
• Bacterial vaginosis: Alters vaginal microbiome
• HIV infection: Increases susceptibility and transmission
• Other concurrent STIs: Indicates exposure and increases risk
• Pregnancy: Screening essential to prevent vertical transmission

Diagnosis

Accurate diagnosis of chlamydia is essential for treatment and preventing transmission. Modern diagnostic methods are highly sensitive and specific, making detection reliable even in asymptomatic cases.

Diagnostic Tests

Nucleic Acid Amplification Tests (NAATs)

The gold standard for chlamydia diagnosis:

• Sensitivity: >90-95% for most specimen types
• Specificity: >99%
• Specimen types:
  • First-catch urine (both men and women)
  • Vaginal swabs (self-collected or clinician-collected)
  • Cervical swabs
  • Urethral swabs (men)
  • Rectal swabs
  • Pharyngeal swabs
• Results: Usually available in 1-3 days

Other Testing Methods

• Cell culture: Less sensitive, rarely used
• Direct fluorescent antibody (DFA): Rapid but less sensitive
• Enzyme immunoassay (EIA): Less sensitive than NAATs
• Point-of-care tests: Rapid results but lower sensitivity

Screening Recommendations

Annual Screening Recommended For:

• All sexually active women under 25 years
• Women 25 and older with risk factors
• All pregnant women at first prenatal visit
• Pregnant women under 25 or at risk in third trimester
• Men who have sex with men (MSM)
  • Urethral testing annually
  • Rectal testing for receptive anal sex
  • Pharyngeal testing for receptive oral sex
• HIV-positive individuals annually
• Individuals with multiple or new partners

Testing Considerations

Timing of Testing

• Can detect infection 1-2 weeks after exposure
• Test of cure 3-4 weeks after treatment completion
• Retest all patients 3 months after treatment (reinfection screening)

Specimen Collection

• Self-collection: Vaginal swabs as accurate as clinician-collected
• First-catch urine: Must be first 20-30 mL of stream
• No urination: For at least 1 hour before urine collection
• Extragenital testing: Based on sexual practices

Partner Testing

• All sexual partners from past 60 days should be tested
• If last sexual contact >60 days, test most recent partner
• Expedited partner therapy (EPT) available in many areas
• Partners should be tested even if asymptomatic

Differential Diagnosis

Other conditions to consider:

• Gonorrhea - Often co-infected
• Trichomoniasis
• Urinary tract infection
• Bacterial vaginosis
• Herpes simplex virus
• Mycoplasma genitalium

Treatment Options

Chlamydia is easily curable with appropriate antibiotic therapy. Early treatment prevents complications and transmission to partners. Treatment recommendations have evolved with emerging antibiotic resistance patterns.

First-Line Treatment

Preferred Regimen (CDC 2021 Guidelines)

• Doxycycline 100 mg orally twice daily for 7 days
  • Now preferred over azithromycin due to increasing resistance
  • Better efficacy for rectal chlamydia
  • Must complete full course
  • Take with food to reduce GI upset

Alternative Regimens

• Azithromycin 1 g orally in a single dose
  • Convenient single-dose therapy
  • May be preferred when adherence is concern
  • Less effective for rectal infections
• Levofloxacin 500 mg orally once daily for 7 days

Special Populations

Pregnancy

• Recommended: Azithromycin 1 g orally in a single dose
• Alternative: Amoxicillin 500 mg orally three times daily for 7 days
• Doxycycline contraindicated in pregnancy
• Test of cure 3-4 weeks after treatment
• Retest in third trimester

Rectal Chlamydia

• Doxycycline 100 mg twice daily for 7 days preferred
• Azithromycin less effective for rectal infections
• 21-day course may be needed for lymphogranuloma venereum

Children

• Weight <45 kg: Erythromycin base 50 mg/kg/day divided into 4 doses for 14 days
• Weight ≥45 kg but <8 years: Azithromycin 1 g orally single dose
• Age ≥8 years: Adult regimens

Treatment Considerations

Important Instructions

• Abstain from sexual activity for 7 days after single-dose therapy
• Abstain until 7-day regimen completed and symptoms resolved
• Partners must be treated before resuming sexual activity
• No alcohol with metronidazole if treating concurrent infections
• Complete entire course even if symptoms improve

Managing Treatment Failure

• True treatment failure is rare with adherence
• Most "failures" are reinfection
• Consider:
  • Reinfection from untreated partner
  • New infection
  • Non-adherence to treatment
  • Alternative diagnosis
• Retreat with different antibiotic if true failure suspected

Partner Treatment

Expedited Partner Therapy (EPT)

• Providing prescriptions or medications to partners without examination
• Legal in many states for heterosexual partners
• Reduces reinfection rates
• Not recommended for MSM or partners with symptoms

Partner Management

• All partners from past 60 days need treatment
• Treat most recent partner if >60 days
• Partners treated empirically without testing
• Provide education about infection and prevention

Follow-Up Care

Test of Cure

• Not routinely recommended except:
  • Pregnancy
  • Persistent symptoms
  • Adherence concerns
  • Rectal infections
• Wait 3-4 weeks after treatment completion
• NAATs may remain positive <3 weeks

Retesting for Reinfection

• All patients should be retested 3 months after treatment
• High reinfection rates (10-20%)
• If 3-month visit not possible, retest whenever seen in next 12 months

Prevention

Prevention of chlamydia involves a combination of behavioral interventions, barrier methods, regular screening, and prompt treatment of infections.

Primary Prevention Strategies

Barrier Methods

• Male condoms:
  • 70-80% effective when used consistently and correctly
  • Latex or polyurethane for latex allergies
  • Must be used for entire sexual encounter
  • New condom for each act
• Female condoms:
  • Similar effectiveness to male condoms
  • Can be inserted up to 8 hours before sex
  • Do not use with male condom
• Dental dams: For oral-vaginal or oral-anal contact

Behavioral Interventions

• Mutual monogamy: With tested, uninfected partner
• Reducing number of partners: Decreases exposure risk
• Partner communication: Discuss STI testing and status
• Avoiding concurrent partnerships: Reduces network transmission
• Delaying sexual debut: For adolescents
• Abstinence: Only 100% effective method

Screening as Prevention

• Regular screening identifies asymptomatic infections
• Early treatment prevents complications
• Reduces transmission to partners
• Cost-effective for high-risk populations
• Home testing options increase access

Biomedical Prevention

Pre-exposure Prophylaxis (PrEP) Research

• Doxycycline PrEP under investigation
• May reduce bacterial STIs in high-risk groups
• Concerns about antibiotic resistance
• Not currently recommended

Vaccines

• No vaccine currently available
• Research ongoing for vaccine development
• Challenges due to multiple serovars

Public Health Approaches

• Partner notification: Health department assistance available
• Expedited partner therapy: Reduces reinfection
• School-based screening: Reaches high-risk adolescents
• Community outreach: Testing in non-clinical settings
• Online resources: Education and home testing options

Education and Counseling

• Comprehensive sex education: Evidence-based curricula
• Risk reduction counseling: Individualized approaches
• Condom demonstration: Proper use techniques
• Regular testing messages: Normalize screening
• Stigma reduction: Encourage open communication

When to See a Doctor

Prompt medical attention is crucial for preventing complications and transmission. Many people with chlamydia have no symptoms, making regular screening essential.

Seek Immediate Medical Care If:

• Severe lower abdominal or pelvic pain
• Fever with pelvic pain (possible PID)
• Heavy or prolonged vaginal bleeding
• Severe testicular pain or swelling
• Eye infection in newborn
• Symptoms during pregnancy

Schedule an Appointment If:

• You have any symptoms of chlamydia
• A sexual partner has been diagnosed with chlamydia or any STI
• You've had unprotected sex with a new partner
• You're due for routine STI screening
• You're pregnant or planning pregnancy
• Symptoms persist after treatment
• You need retesting after treatment

Routine Screening Schedule:

• Sexually active women under 25: Annually
• Women 25+ with risk factors: Annually
• All pregnant women: First prenatal visit
• MSM: At least annually, more frequently if high risk
• After treatment: Retest at 3 months

What to Expect at Your Visit:

• Confidential sexual history
• Physical examination if symptomatic
• Simple urine test or swab
• Testing for other STIs
• Treatment if positive
• Partner notification assistance
• Prevention counseling

Related Conditions

Several conditions are associated with or may be confused with chlamydia:

• Gonorrhea - Often co-infected with chlamydia
• Pelvic Inflammatory Disease - Major complication of untreated chlamydia
• Urethritis - Inflammation often caused by chlamydia
• Cervicitis - Cervical inflammation from chlamydia
• Epididymitis - Testicular complication in men
• Trichomoniasis - Another common STI
• Bacterial Vaginosis - Increases chlamydia risk
• Reactive Arthritis - Post-infectious complication
• Infertility - Long-term consequence of PID
• Ectopic Pregnancy - Risk increased after PID

Frequently Asked Questions

References

1. Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1-187.
2. Centers for Disease Control and Prevention. Chlamydia - CDC Fact Sheet (Detailed). Updated 2022.
3. Elwell C, Mirrashidi K, Engel J. Chlamydia cell biology and pathogenesis. Nat Rev Microbiol. 2016;14(6):385-400.
4. Geisler WM. Duration of untreated, uncomplicated Chlamydia trachomatis genital infection and factors associated with chlamydia resolution: a review of human studies. J Infect Dis. 2010;201(Suppl 2):S104-113.
5. Price MJ, Ades AE, Soldan K, et al. The natural history of Chlamydia trachomatis infection in women: a multi-parameter evidence synthesis. Health Technol Assess. 2016;20(22):1-250.
6. O'Connell CM, Ferone ME. Chlamydia trachomatis Genital Infections. Microb Cell. 2016;3(9):390-403.
7. Haggerty CL, Gottlieb SL, Taylor BD, et al. Risk of sequelae after Chlamydia trachomatis genital infection in women. J Infect Dis. 2010;201(Suppl 2):S134-155.