86: Chlamydial Infection

I. 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 can cause conjunctivitis and pneumonia.

II. 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%. 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.

III. PATHOPHYSIOLOGY

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.

IV. 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 membranes of an infected mother.

V. CLINICAL PRESENTATION

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.

VI. DIAGNOSIS

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 ...