86: Chlamydial Infection

Chlamydia trachomatis is an obligate intracellular small Gram-negative bacterium that possesses a cell wall, contains DNA and RNA, and can be inactivated by several antimicrobial agents. It is the most common cause of sexually transmitted genital infections. It may cause urethritis, cervicitis, and salpingitis in the mother. In the infant, it can cause conjunctivitis and pneumonia.

The prevalence of C. trachomatis in pregnant women varies from 2–15%. The risk of infection to infants born to infected mothers is high; conjunctivitis occurs in 25–50% and pneumonia in 5–20%. In the Netherlands, where prenatal screening is not routine, one study showed C. trachomatis to be responsible for 64% of all cases of neonatal conjunctivitis.

Chlamydia trachomatis subtypes B and D through K cause the sexually transmitted form of the disease and the associated neonatal infection. They frequently cause a benign subclinical infection. The infant acquires infection during vaginal delivery through an infected cervix. Infection after cesarean delivery is rare and usually occurs with early rupture of amniotic membranes; however, infection associated with intact membranes has been reported. Population-based studies suggest that maternal C. trachomatis infection is associated with an increased risk of preterm delivery and premature rupture of membranes.

Risk is inversely proportional to gestational age. Risk factors include vaginal delivery of an infant with an infected mother and cesarean delivery with early rupture of the amniotic membranes of an infected mother.

1. Conjunctivitis. See Chapter 53.

2. Pneumonia. This is one of the most common forms of pneumonia in the first 3 months of life. The respiratory tract may be directly infected during delivery. Approximately half of infants presenting with pneumonia have concurrent or previous conjunctivitis. Pneumonia usually presents at 3–11 weeks of life. The infants experience a gradual increase in symptoms over several weeks. Initially, there is often 1–2 weeks of mucoid rhinorrhea followed by cough and increasing respiratory rate. More than 95% of cases are afebrile. The cough is characteristic, paroxysmal, and staccato, and it interferes with sleeping and eating. Approximately a third of infants have otitis media. Preterm infants may present with apneic spells. Chlamydia trachomatis has been isolated from tracheal secretions of preterm infants with pneumonia in the first week after birth.

1. Laboratory studies

   1. Tissue culture. Because chlamydiae are obligate intracellular organisms, culture specimens must contain epithelial cells. Culture of the organism is the gold standard for diagnosing neonatal conjunctivitis and pneumonia. The specificity and sensitivity of culture is nearly 100% with adequate sampling and transport. Material should be obtained from the tarsal conjunctiva (for conjunctivitis) or from nasopharyngeal aspiration or deep suctioning of the trachea (for suspected pneumonia).

   2. Nucleic acid amplification tests (NAAT). These use methods to amplify C. trachomatis DNA or RNA sequences. Currently available tests are polymerase chain reaction (Amplicor), transcription-mediated amplification (Aptima Combo 2), and strand displacement amplification (ProbeTec). These tests are approved by the U.S. Food and Drug Administration (FDA) to be used in adults (largely replaced tissue culture as the diagnostic method of choice), but no sufficient data are available in infants.

   3. Antigen detection tests. Include direct fluorescent antibody and enzyme immunoassay tests. These tests appear to be sensitive and specific when used with conjunctival specimens, but the sensitivity with nasopharyngeal samples is poor. These tests are used infrequently and have largely been replaced by NAAT.

   4. Serum anti-chlamydial antibody (IgM) concentration. Difficult to determine and not widely available. In children with pneumonia, a titer >1:32 is diagnostic of infection.

   5. Other tests. In cases of pneumonia, the white blood cell count is normal, but there is eosinophilia in 70% of cases. Blood gas measurements show mild to moderate hypoxemia.

2. Imaging and other studies. In cases of pneumonia, the chest radiograph may reveal hyperexpansion of the lungs, with bilateral diffuse interstitial or alveolar infiltrates.

Isolation precautions for all infectious diseases, including maternal and neonatal precautions, breast-feeding, and visiting issues, can be found in Appendix F.

1. Prevention. In high-risk populations, identification and treatment of infected mothers can prevent disease in the infant. The U.S. Centers for Disease Control and Prevention (CDC) recommends that all pregnant women be screened for chlamydia at the first prenatal visit. Women under age 25 and those at increased risk for chlamydial infection should have repeat testing in the third trimester. Infants born to mothers known to have untreated chlamydial infection should be monitored clinically. Prophylactic antimicrobial treatment is no longer recommended because the efficacy of such therapy is unknown. Additionally, oral erythromycin, the agent most commonly used, is associated with significant risk for infantile hypertrophic pyloric stenosis (IHPS).

2. Conjunctivitis. Treated with oral erythromycin base or ethylsuccinate (50 mg/kg/d in 4 divided doses) for 14 days. Topical therapy is ineffective and unnecessary.

3. Pneumonia. Also treated with erythromycin, 50 mg/kg/d in 4 divided doses for 14 days. This not only shortens the clinical course but decreases the duration of nasopharyngeal shedding. Because the efficacy of erythromycin therapy is ∼80%, a second course may be required, and follow-up of infants is recommended. Limited data on azithromycin therapy for treatment of C. trachomatis infections in infants suggest that dosing of 20 mg/kg as a single daily dose for 3 days may be effective. The mother and her sexual partner(s) should be evaluated and treated. IHPS may occur when infants are treated with erythromycin in the first 2 weeks of life. Because alternative therapies for C. trachomatis in the newborn are not well studied, the American Academy of Pediatrics and CDC continue to recommend erythromycin to treat neonatal chlamydia infection. Parents should be informed about the signs and potential risks of developing IHPS. Cases of IHPS after the use of oral erythromycin should be reported to MedWatch, the FDA Safety Information and Adverse Event Reporting Program. No isolation measures are necessary.

Infants who are diagnosed and treated early generally recover. Experimental studies suggest that neonatal chlamydial pneumonia, especially in preterm neonates, may cause airway hyperreactivity and respiratory dysfunction that continues into adulthood.