Pneumonia, Neonatal (Group B Streptococcus)

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

Etiology/Pathophysiology:
There are three ways for the baby to acquire a neonatal pneumonia. First is infection acquired prior to birth by an ascending route or transplacental route. Classically this is Group B Streptococcus in the mother's vagina which passes to the infant during birth, particularly in cases with prolonged rupture of membranes and prolonged labor. Other normal inhabitants of the birth canal - staph, strep, diphtheroids, anaerobes, E. coli and Listeria - are other pathogens that may cause neonatal pneumonia. Second is infection acquired by aspiration during delivery, with the pathogens remaining the same. Third is via infection acquired after birth.

Pathology:
There is a less uniform distribution of hyaline membranes in collapsed alveoli than is seen in hyaline membrane disease. There are cocci in the alveolar membrane and in the interstitial inflammatory exudate.

Imaging Findings:
Ascending infection may resemble hyaline membrane disease very closely, especially in smaller infants. Most commonly seen are extensive granular confluent infiltrates whose distribution is often less uniform than that of hyaline membrane disease. There is less atelectasis than in hyaline membrane disease. May have pleural fluid and a normal lung volume, further distinguishing factors from hyaline membrane disease. Infection acquired perinatally often has a confluent miliary or nodular pattern that looks like meconium aspiration or transient tachypnea of the newborn while postnatally acquired infection often has a patchy more asymmetric pattern that looks like infection in older children.

DDX:

• Hyaline Membrane Disease - usually has a uniform distribution of pulmonary opacities, never has pleural effusions, has a decreased lung volume.
• Meconium Aspiration - usually has nodular non homogeneous densities, may have pleural effusions, usually has an increased lung volume.
• Transient Tachypnea of the Newborn - usually has non homogeneous densities, may have pleural fluid.

References:
See References Chapter.

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