Community-Acquired Pneumonia

Pneumonia is defined as acute infection of the pulmonary parenchyma. The infection can be caused by bacterial or viral pathogens and can be acquired in the community (community-acquired pneumonia, CAP) or within the hospital setting (hospital-acquired [nosocomial] pneumonia). Pneumonia is the leading cause of death in children worldwide. In this section, we focus on the diagnosis and treatment of CAP in infants older than one month. The management of pneumonia in the neonate is beyond the scope of this guide.

Clinical presentation: The clinical presentation of pneumonia differs depending on etiology, host immune factors, and age. Children with pneumonia may present with fever, cough, tachypnea, fatigue, and hypoxemia. They may have shortness of breath with activity and demonstrate use of accessory muscles (suprasternal, intercostal, or subcostal muscles) when breathing. Signs of more-severe respiratory distress include altered mental status and grunting.

Pneumonia in Infants Aged 1 to 3 Months

Bacterial Pneumonia in Infants

Chlamydia trachomatis is a common cause of bacterial pneumonia in afebrile infants between 2 and 12 weeks of age. Infants with Chlamydia pneumoniae may present with upper respiratory symptoms and lung hyperinflation on chest radiograph. Infection is acquired from the mother through the genital tract during delivery. Since many women are asymptomatic, the mother may be unaware of the infection. This bacterial infection is typically treated with a macrolide (either azithromycin or erythromycin). Parents of infants <6 weeks old who are treated with macrolide antibiotics should be counseled about the risk of infantile hypertrophic pyloric stenosis.

Bordetella pertussis is another organism that causes bacterial pneumonia in this age group. B. pertussis infection, or whooping cough, classically presents with three stages:

• catarrhal (characterized by upper respiratory symptoms)

• paroxysmal (characterized by coughing spells)

• convalescent

Infants with pertussis may not present with classic whooping, and clinicians must have a high index of suspicion for pertussis, particularly because infants in the paroxysmal stage can become apneic. An audio recording of an infant with whooping cough can be heard here.

Pertussis is often associated with upper respiratory tract disease. However, infants with pertussis are at risk of severe lower respiratory tract disease. Infants with B. pertussis-associated pneumonia should be admitted to the hospital because they are at risk of experiencing the following complications:

• hypoxia

• apnea

• seizures

• hypotension/shock

• renal failure

• pulmonary hypertension

Young children with pertussis typically have markedly elevated leukocytosis (white blood cell [WBC] >20,000 cells/μL) with associated lymphocytosis (>50%). Some infectious disease experts recommend exchange transfusion for infants with pertussis who are younger than 4 months and have significant leukocytosis (WBC >25,000 cells/μL) and pulmonary hypertension.

Risk factors associated with death in infants with pertussis include the following:

• low birth weight

• high WBC count

• pulmonary hypertension

• seizures

Azithromycin is the drug of choice for treatment of pertussis, but caregivers should be counseled about the associated risk of pyloric stenosis when used in children younger than 6 weeks.

Vaccination of pregnant mothers, caregivers, and infants is the mainstay of prevention. Pertussis rates in the United States have increased, despite recent recommendations for immunization of caregivers and families of young infants. The increased rates are thought to be in part due to insufficient herd immunity and waning immunity.

(Source: Pertussis Trends in the United States. CDC. National Notifiable Diseases Surveillance System (NNDSS). Last reviewed August 2022.)

Viral Pneumonia in Infants

Viruses may also cause pneumonia in young infants. Early symptoms of viral pneumonia are the same as for bacterial pneumonia. There is no effective treatment for viral pneumonia, and it usually resolves on its own. Viral pneumonias may make a child susceptible to bacterial pneumonia. Viral causes of pneumonia in this age group include:

• respiratory syncytial virus (RSV)

• human parainfluenza virus

• human metapneumovirus

• severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

Pneumonia in Children Older Than 3 Months

Viral Pneumonia in Children Older Than 3 Months

Pneumonia in early childhood is most commonly caused by viruses. Wheezing and diffuse rhonchi may be heard on examination.

Viral etiologies of pneumonia include:

• RSV

• human metapneumovirus

• human parainfluenza

• influenzas A and B

• adenovirus and rhinovirus (less common causes of lower respiratory tract infections)

• SARS-CoV-2

Immunocompromised patients and neonates are at greater risk for severe disease from viral infections and may develop lower respiratory tract infections with varicella-zoster virus (VZV), cytomegalovirus (CMV), and herpes simplex virus (HSV).

Antiviral agents are generally not used to treat viral pneumonia in the outpatient setting, except for treatment of pneumonia due to influenza and SARS-CoV-2. Children should not receive antibiotics when a viral etiology is suspected or confirmed as the cause of lower respiratory tract infection.

Bacterial Pneumonia in Children Older Than 3 Months

Listed below are common causes of bacterial pneumonia in infants and children older than 3 months:

• Streptococcus pneumoniae is the most common cause of bacterial pneumonia in children. However, the incidence of CAP secondary to S. pneumoniae has decreased since the introduction of the pneumococcal conjugate vaccine. Elevated WBC count (WBC >15,000/μL), elevated C-reactive protein (CRP >35-60 mg/L), and lobar consolidation on chest radiograph suggest a bacterial etiology.

• Staphylococcus aureus, both methicillin-sensitive and methicillin-resistant strains, should be considered as a potential cause of bacterial pneumonia in children with severe disease requiring intensive care unit (ICU) admission, multifocal infections, or in patients with necrotizing pneumonia. S. aureus is one of the most frequently detected bacteria in patients with bacterial pneumonia complicating influenza infection.

• Mycoplasma pneumoniae causes an atypical pneumonia and is more common in children age 5 years and older. Symptoms are generally less severe, and pneumonias tend to be self-limited. Patients with M. pneumoniae typically have a nonproductive cough and occasionally have wheezing. About 10% of children with M. pneumoniae may develop erythema multiforme.

• Haemophilus influenzae, Chlamydia pneumoniae, and Moraxella cattarhalis are less common causes of bacterial pneumonia and are associated with less severe disease.

Treatment of bacterial CAP in children >3 months: The Infectious Diseases Society of America (IDSA) has issued evidenced-based guidelines for management of community-acquired pneumonia (CAP) in infants and children that include the following treatment recommendations:

• High-dose amoxicillin is the antibiotic of choice for children older than 3 months with bacterial CAP who do not require hospitalization. Amoxicillin is preferred because it is effective against the majority of bacterial pathogens for CAP, well tolerated, and inexpensive. The high dose is for empiric treatment of antibiotic-resistant S. pneumoniae.

• An alternative to amoxicillin for children with non-type I hypersensitivity reactions to penicillin is a second- or third-generation cephalosporin (e.g., cefdinir). Clindamycin or a macrolide are also alternatives, with the caveat that local resistance rates may be high for these drugs.

• In children with suspected S. aureus infection, treatment should include coverage of methicillin-resistant S. aureus with either vancomycin or clindamycin, depending on local susceptibilities.

• For patients who require hospitalization, the choice of antimicrobials can vary with clinical presentation and age. However, for uncomplicated cases in children older than 6 months, ampicillin is recommended. In unimmunized children at risk of disease secondary to Haemophilus influenzae type B or pneumococcus, or in areas with high rates of resistant pneumococcus, ceftriaxone should be used.

Indications for hospitalization: Indications for hospitalization of children with CAP include inability to tolerate oral antibiotics, respiratory distress, and oxygen requirement. Some patients with severe viral or bacterial pneumonia may require oxygen supplementation and mechanical ventilation. In severe cases, extracorporeal membrane oxygenation (ECMO) has been used to improve oxygenation while reducing the need for positive pressure ventilation.

(Source: Community-Acquired Pneumonia Requiring Hospitalization Among U.S. Children. N Engl J Med 2015.)

Complications of Pneumonia

Most episodes of pneumonia in children will resolve spontaneously or with antimicrobial therapy. However, the following groups of patients are more likely to develop complications:

• patients with underlying diseases

• patients with anatomic or functional abnormalities

• immunocompromised patients

Major complications of pneumonia:

• abscess

• empyema

• apnea or respiratory failure

• bacteremia and sepsis

• necrotizing pneumonia

• pleural effusion

• pericardial effusion

• pneumothorax

• pneumatocele

Empyema: The most common complication is empyema with or without lung abscess. Empyema is the development of a purulent effusion in the parapneumonic space. Children with empyema and lung abscesses will generally have diminished breath sounds and prolonged fever despite adequate antibiotic therapy. The diagnosis of complicated pneumonia is usually made by imaging, either with chest x-ray, ultrasound, or computed tomography. Surgical intervention (either chest-tube placement or decortication) and prolonged antibiotic therapy may be required. The decision to perform surgery is typically based on the size and characteristics of the effusion.

(Source: The Management of Community-Acquired Pneumonia in Infants and Children Older Than 3 Months of Age: Clinical Practice Guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America. Clin Infect Dis 2011.)