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A lower respiratory tract infection (LRI) develops in one in three children in the first year of life. Twenty-nine percent of these children develop pneumonia, 15% develop croup, 34% tracheobronchitis, and 29% bronchiolitis.

Pneumonia in newborns

Group B streptococcal disease is the most common cause of pneumonia in the newborn. The infection usually is acquired in utero. Prenatal screening of expectant mothers and intrapartum prophylaxis of colonized mothers with IV ampicillin decreases the incidence.

Initial therapy of pneumonia in newborns consists of ampicillin (100 mg/kg IV initial dose, followed by 200 mg/kg/day divided QID) and gentamicin (2.5 mg/kg IV initial dose, followed by 7.5 mg/kg/day divided q8h).

Pneumonia in infants (2 weeks to 6 months)

Febrile/ill-appearing infants

Pathogens in this age group include Streptococcus pneumoniae and Haemophilus influenzae serotype B (HIB). HIB has all but disappeared because of vaccination. Staphylococcus aureus is also.

Afebrile/well-appearing infants

In infants with afebrile pneumonia, the pathogens most commonly are Chlamydia trachomatis (25%), Ureaplasma urealyticum (21%), cytomegalovirus (20%), and Pneumocystis carinii (18%).

Chlamydia antigens can be detected by direct flourescent antibody and enzyme-linked immunoassay techniques.

RSV, adenovirus, and the parainfluenza viruses also can cause pneumonia in otherwise well infants. Viral antigen detection kits are available for these common viral pathogens.

Bordetella pertussis infection may cause paroxysms of cough.

Pneumonia in toddlers and preschoolers

Afebrile/well-appearing toddlers and preschoolers

The majority of pneumonia among in this age group is caused by viral infection with RSV, parainfluenza, adenovirus, or influenza, or by other viruses (enterovirus, rhinovirus).

Febrile/ill-appearing Toddlers and Preschoolers

Pneumococcus is the most common bacterial pathogen causing febrile pneumonia in children and adults. The syndrome is characterized by acute onset of high, spiking fever, with chills, cough and sputum production. Crackles may be heard on auscultation.

Pneumonia in children and adolescents

Atypical bacteria, Mycoplasma pneumoniae and C pneumoniae, are responsible for a significant proportion of afebrile lower respiratory tract disease in adolescents and school-age children.

Atypical pneumonia may be associated with a prodrome of headache and abdominal symptoms.