Chapter 35: Infectious Disease Issues in the NICU Graduate

Infectious Disease Issues in the NICU Graduate

Infants can acquire infection prenatally through transplacental transfer, perinatally during birth, or postnatally. Newborn infants are relatively immunocompromised and at high risk of developing infections. The immune system of the newborn is immature and their skin, an important barrier to infection, is not fully developed. Infants admitted to the NICU often require invasive methods of support (eg, central venous lines or endotracheal tubes), which can serve as routes for infection. Infections result in significant mortality and both short- and long-term morbidities among survivors. In this chapter, we will discuss infections occurring in the newborn period, how these infections are treated, and long-term complications in survivors.

I. Maternal infections

1. Cytomegalovirus infection

   1. Incidence

      1. Cytomegalovirus (CMV), the most common congenital viral infection, affects 0.4% to 2.3% of all live births.

      2. CMV infections occur during all seasons and the incidence is inversely proportional to socioeconomic status.

   2. Pathophysiology (mode of transmission)

      1. Transmission can occur through contact with infected body fluids including blood, amniotic fluid, saliva, human milk, and urine.

      2. Infants can become infected prenatally, during delivery, or postnatally.

      3. Fetal transmission occurs during maternal primary infection, reactivation, or reinfection with another strain, though fetal transmission is most likely during maternal primary infection.

      4. 15% to 59% of preterm infants exposed to CMV positive maternal breast milk develop CMV infection.

      5. Freezing breast milk reduces the rate of CMV transmission, but does not eliminate it.

      6. Blood products that are leukoreduced reduce the chance of CMV transmission, but do not eliminate it.

   3. Clinical presentation

      1. Ninety percent of prenatally infected term infants are asymptomatic at birth.

      2. Symptomatic infants can present with intrauterine growth restriction, microcephaly, hepatosplenomegaly, blueberry muffin rash, and intracranial calcifications (Table 35-1).

      3. Few term infants develop symptomatic infection postnatally because of transplacentally acquired antibody.

      4. 15% to 25% of infants exposed to CMV via breast milk will develop a sepsis-like condition.

      5. CMV infection is the most common cause of acquired sensorineural hearing loss in infants.

         • Five percent of infants born with congenital CMV have hearing loss at birth, and 15% will have hearing loss by 72 months of age.

         • Infants with symptomatic infection at birth are more likely to have hearing loss.

      6. Seventy percent of symptomatic infants develop mental retardation, making CMV one of the most common infectious causes of mental retardation (Table 35-2).

   4. Diagnosis

      1. Start with urine or saliva CMV shell-vial culture.

      2. If urine CMV is negative, and clinical presentation is suspicious, the uroepithelium may not have yet been seeded. Send blood CMV PCR or repeat urine CMV culture.

      3. If infant CMV urine/saliva culture is positive and congenital CMV transmission is suspected, the following testing should be completed.

         • Blood CMV quantitative PCR

         • CBC with differential, LFTs

         • Eye examination

         • Hearing evaluation

         • Head ultrasound and if indicated, brain MRI

         • If CNS involvement is suspected, LP for cell counts, protein, glucose, and CMV PCR

   5. Management

      1. If CNS involvement is proven or suspected (hearing loss, retinal ...