Definition.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 may cause conjunctivitis and pneumonia.
Incidence. 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%.
Pathophysiology.C. 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. A recent population-based study from Washington State suggested that maternal C. trachomatis infection is associated with an increased risk of preterm delivery and premature rupture of membranes.
Risk factors. 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 membrane of an infected mother.
Conjunctivitis. See Chapter 47.
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. C. trachomatis has been isolated from tracheal secretions of preterm infants with pneumonia in the first week after birth.
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).
Nucleic acid amplification (NAA) tests use methods to amplify C. trachomatis DNA or RNA sequences. Currently available tests are polymerase chain reaction (Amplicor), transcription-mediated amplification (Aptima Comb 2), and strand displacement amplification (ProbeTec). These tests are approved by the United States Food and Drug Administration (FDA) to be used in adults, but no sufficient data are available in infants.
Antigen detection tests include direct fluorescent antibody and enzyme immunoassay tests. These tests appear to be sensitive and specific ...
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