Pneumonia is the most common invasive bacterial infection after primary sepsis. Early-onset pneumonia is part of generalized sepsis that first manifests at or within hours of birth (see Neonatal Sepsis). Late-onset pneumonia usually occurs after 7 days of age, most commonly in neonatal intensive care units among infants who require prolonged endotracheal intubation because of lung disease (called ventilator-associated pneumonia).
Organisms are acquired from the maternal genital tract or the nursery. These organisms include gram-positive cocci (eg, groups A and B streptococci, both methicillin-sensitive and methicillin-resistant Staphylococcus aureus) and gram-negative bacilli (eg, Escherichia coli, Klebsiella species, Proteus species). In infants who have received broad-spectrum antibiotics, many other pathogens may be found, including Pseudomonas, Citrobacter, Bacillus, and Serratia. Viruses or fungi cause some cases.
Evaluation includes chest x-ray, pulse oximetry, blood cultures, and Gram stain and culture of tracheal aspirate.
New, persistent infiltrates should be visible on chest x-ray but may be difficult to recognize if the infant has severe bronchopulmonary dysplasia.
If Gram stain of tracheal aspirate shows a significant number of polymorphonuclear leukocytes and a single organism that is consistent with the one that grows from culture of the tracheal aspirate, the likelihood increases that this organism is the cause of the pneumonia. Because bacterial pneumonia in neonates may disseminate, a full evaluation for sepsis, including a lumbar puncture, should also be done. However, blood cultures are positive in only 2 to 5% of cases of hospital-acquired pneumonia.
Antimicrobial therapy in early-onset disease is similar to that for neonatal sepsis. Vancomycin (see table Vancomycin Dosage for Neonates) and a broad-spectrum beta-lactam drug such as meropenem, piperacillin/tazobactam, or cefepime (see Table: Recommended Dosages of Selected Parenteral Antibiotics for Neonates) are the initial treatment of choice for most late-onset hospital-acquired pneumonia. This regimen treats sepsis as well as pneumonia with typical hospital-acquired pathogens including P. aeruginosa. Local patterns of infection and bacterial resistance should always be used to help guide empiric choices of antimicrobials. More specific antibiotics are substituted after sensitivity results are available. General treatment is the same as that for neonatal sepsis.
Exposure to chlamydial organisms during delivery may result in development of chlamydial pneumonia at 2 to 18 weeks. Infants are tachypneic but usually not critically ill and may also have a history of conjunctivitis caused by the same organism. Eosinophilia may be present, and x-rays show bilateral interstitial infiltrates with hyperinflation.
Treatment with erythromycin 12.5 mg/kg orally every 6 hours for 14 days or azithromycin 20 mg/kg orally/IV once a day for 3 days typically resolves the pneumonia. Occasionally, however, a second course may be necessary (see Table: Recommended Dosages of Selected Oral Antibiotics for Neonates*). Because erythromycins in neonates may cause hypertrophic pyloric stenosis (HPS), all neonates treated with erythromycin or azithromycin should be monitored for symptoms and signs of HPS and their parents should be counseled regarding potential risks.
The diagnosis of pneumonia secondary to Chlamydia trachomatis should prompt an evaluation of the mother and her partner because untreated maternal chlamydial infection may have complications such as pelvic inflammatory disease and sterility.