Aetiology of CAP in neonates and children younger than 2 months

In neonates, the organisms associated with early-onset pneumonia (occurring within 72 hours of birth) are usually acquired from the maternal perineal flora. When assessing neonatal pneumonia, it is helpful to review the results of maternal bacterial screening and other maternal investigations for infection or colonisation. The pathogens likely to cause pneumonia in the neonatal period include Streptococcus agalactiae (group B streptococcus) and Escherichia coli. In neonates, herpes simplex virus (HSV) (acquired from the birthing parent [eg mother]) can present as pneumonitis – see Initial management of neonates suspected to have or who are at risk of acquiring herpes simplex virus infection.

After the neonatal period, pathogens likely to cause pneumonia include:

• respiratory viruses (eg adenovirus, coronavirus, human metapneumovirus [hMPV], influenza virus, parainfluenza virus, respiratory syncytial virus [RSV]), which make up to 70% of community-acquired pneumonia (CAP) in children
• Streptococcus pneumoniae, one of the most common bacterial pathogens in children 1 month or older
• Mycoplasma pneumoniae, one of the most common bacterial pathogens in children 1 month or older (however, antibiotic therapy is often not required).

For all neonates and children younger than 2 months, pathogens likely to cause pneumonia include:

• Haemophilus influenzae, which can cause late-onset pneumonia (occurring more than 72 hours after birth)
• Staphylococcus aureus, an important cause of complicated CAP in children of all ages (but an uncommon cause of CAP in neonates). Parapneumonic effusion, empyema and lung abscess are complications of staphylococcal pneumonia in children – seek expert advice for management.

Chlamydia trachomatis¹ and Bordetella pertussis are less common pathogens in neonates and children younger than 2 months with CAP. If Listeria monocytogenes, Mycobacterium tuberculosis, Pneumocystis jirovecii or cytomegalovirus are suspected, seek expert advice.