Update on Pediatric Pneumonia: Causes-Treatment Options

Pneumonia is one of the most common conditions seen by primary care physicians who treat children. Respiratory symptoms are among the most common reasons why outpatients seek medical care. The distinction between upper respiratory tract disease and pneumonia should be made so that pneumonia is managed appropriately.

Here we summarize the evaluation of pediatric pneumonia and offer our management recommendations-based on a literature review and on clinical experience-in the outpatient setting.

EPIDEMIOLOGY AND ETIOLOGY
According to World Health Organization, about 150 million cases of pneumonia occur annually in children younger than age 5 years. About 20 million cases are severe enough to require hospital admission, and 2 million children die worldwide. The majority of these deaths occur in Africa and Southeast Asia. Mortality is much lower in the United States, but morbidity is substantial.

Due to person-to-person spread because of overcrowding and also because of decreased  mucociliary clearance from dry air, pneumonia is more common during winter in temperate climates. The incidence of pneumonia is higher among boys, children from lower socioeconomic levels, and those exposed to smoke. 

The exact cause of pneumonia is not determined in most pediatric cases because of the difficulty in obtaining sputum specimens and the low incidence of bacteremia in children. Respiratory viruses are a major cause of pneumonia and occur frequently in all age groups-especially in infants and young children. The most common causes of pneumonia include influenza A and B viruses; respiratory syncytial virus (RSV); and Haemophilus parainfluenzae types 1, 2, and 3. Adenovirus and rhinovirus can also cause pneumonia. The importance of metapneumovirus as a causative agent of childhood pneumonia is still being clarified, as is its role in producing more severe symptoms if coinfection with RSV is present.

TABLE

Patient age, likely bacterial pathogens, and empiric outpatient antibiotic treatment

Certain organisms cause pneumonia at particular ages (Table). This makes it possible to select antimicrobials based on a patient's age. Neonates can become infected with maternal vaginal and rectal flora; therefore, group B streptococci (Streptococcus agalactiae), Gram-negative bacilli (Escherichia coli in particular), and rarely, Listeria monocytogenes are the causes of pneumonia in this age group. In the developing world, Staphylococcus aureus often affects newborns.

From 1 month to 3 to 4 months of age, viruses are the most common pathogens. In infants between 1 and 3 months viruses are the most common cause of pneumonia. However, group B streptococci and organisms encountered by older children (see Table) occasionally cause pneumonia, along with Chlamydia trachomatis. This atypical pathogen is of particular concern in children between 2 and 19 weeks old. Infection with Ureaplasma urealyticum may also present as afebrile pneumonia, but its role in causing disease in young, healthy infants is controversial.

In older infants and preschoolers (those younger than 5 years), viruses-especially RSV and parainfluenza-continue to be leading causes of pneumonia. In children older than 5 years, S pneumoniae and Mycoplasma pneumoniae play the most important roles. In at-risk populations, Mycobacterium tuberculosis may be a causative organism.

The atypical pathogens M pneumoniae and Chlamydia pneumoniae are, respectively, the second and third most commonly identified bacterial causes of community-acquired pneumonia and are especially prevalent in the 5- to 10-year-old age group. However, preschool-aged children are also at risk. Approximately one-quarter of patients may have a mixed bacterial and viral infection.

However, even after extensive evaluation. the causative organism for pneumonia can be identified in fewer than half the patients.

CLINICAL PRESENTATION
The type of pneumonia and age of the patient affect the clinical presentation. In general, bacterial
pneumonia presents abruptly with high fever and may be accompanied by a productive cough. Viral or atypical pneumonia can present insidiously with upper respiratory tract symptoms, wheezing, and minimal fever.

Neonates with pneumonia display respiratory distress, temperature instability, and lethargy. Early onset of group B streptococcal disease usually occurs within the first 24 hours of life, but it can occur at any time between 0 and 6 days of age.
 
The infant with pneumonia in the first several months of life may be febrile, tachypneic or apneic, and irritable. Fever and tachypnea may be the only findings in a young infant or toddler with pneumonia. Atypical pathogens (ie, C trachomatis) can lead to an afebrile illness accompanied by cough, tachypnea, or wheezing.

The older child with bacterial pneumonia will experience abrupt onset of fever, cough, and malaise. Minimal fever, malaise, and lingering cough typify atypical pneumonia. Poor oral intake, nausea, vomiting, and abdominal pain may manifest in any person with pneumonia.

EVALUATION
The patient's history of present illness and past medical history are essential in determining the possible cause of the pneumonia. Note the patient's immune status: an immunocompromised child may have an opportunistic infection (with Pneumocystis jiroveci for example) in addition to infection with the typical and atypical organisms that an immunocompetent child may encounter. A history of international travel and the time of year that the symptoms are occurring expand the list of possible pathogens.

During the physical examination, determine the respiratory rate for a full minute-especially in younger patients-and compare the rate with normal values for that child's age group because tachypnea is the most sensitive and specific sign of pneumonia. Observe the patient for any signs of respiratory distress (retractions, flaring, grunting, cyanosis) and auscultate the chest for wheezing, rhonchi, or decreased breath sounds. Wheezing is usually associated with viral infection-not bacterial infection. In older patients, it may be possible to check for signs of lower respiratory tract disease, such as dullness to percussion, increased fremitus, and egophony.

When you suspect viral pneumonia or if influenza and/or RSV infection are prevalent in your
community, perform a rapid antigen test (if readily available) on nasopharyngeal secretions, which can lead to timely diagnosis. Serologic tests may be performed to diagnose Mycoplasma, Chlamydia, and Legionella infections. A urinary antigen test may also be performed to diagnose Legionella.

The recently published guidelines for the management of community acquired pneumonia  include a recommdation against the use of a urinary antigen test for the diagnosis of pneumoncoccal pneumonia.¹

The difficulty of obtaining an adequate sputum sample in a young child precludes sputum analysis from being a routine component of the outpatient evaluation of uncomplicated pediatric pneumonia. A total serum white blood cell count and differential and measurement of sedimentation rate and C-reactive protein level are nonspecific aids that may provide evidence for a viral or bacterial cause. Blood cultures are of limited value in the diagnosis of pneumonia because results are positive in fewer than 10% of patients with pneumonia; however, cultures should be obtained in the young febrile infant-especially if that infant is not fully immunized against pneumococci.¹  Blood cultures should also be obtained in any child who does not improve or who worsens despite treatment with antibiotics.

FIGURE 1

Anteroposterior and lateral chest radiographs help reveal areas of consolidation or
interstitial disease in the ill patient (Figure 1). The pattern of abnormal findings on
x-ray films provides a clue to the possible causative agent. Bacteria (S pneumoniae)
are more likely to produce a lobar pattern and viral or atypical pathogens are more
likely to produce an interstitial pattern. These radiographic descriptions are not
absolute: bacterial and viral pathogens can produce various patterns of radiographic
findings.

During outpatient treatment, order follow-up chest radiographs when you suspect a complication such as pleural effusion or empyema, evidenced by chest pain, failure to respond to antibiotics, recurrence of fever, and worsening respiratory tract signs. Upright and lateral decubitus radiographs also may be necessary in this setting. After a patient completes therapy for uncomplicated pneumonia, repeated chest radiographs are not necessary; if they are obtained, however, be aware that initial radiographic abnormalities may take 6 or more weeks to resolve.
 

The chest radiograph is not capable of detecting all pneumonias. High-resolution CT scans can detect infiltrates that are not evident on plain chest radiographs. A chest CT scan may be required in a pediatric patient with normal chest films and serious or unexplained respiratory symptoms-especially a febrile immunocompromised patient. More invasive testing is not routine in the general pediatric clinic. In complicated cases, referral for bronchoscopy; bronchoalveolar lavage; or collection of a pleural fluid sample for culture, Gram stain, and analysis (cell count; levels of glucose, protein, and lactate dehydrogenase; pH; and specific gravity) may be needed.

A tuberculin skin test may be performed in patients who are at high risk for contracting tuberculosis.

TREATMENT
The patient’s age, history, clinical presentation, and radiographic findings guide therapy. Should the child be hospitalized or treated as an outpatient? Generally those who require hospitalization are younger than 3 to 6 months; have persistent hypoxemia and require supplemental oxygen; appear toxic; require IV hydration; or who have underlying chronic conditions, such as cystic fibrosis. If outpatient compliance with prescribed treatment is a concern due to social circumstances, hospitalization is advised.

If you suspect viral infection, supportive care includes adequate hydration, oxygen, and analgesics for general discomfort. If influenza is diagnosed, the use of anti-influenza medications should be considered on a case-by-case basis and ideally administered within 48 hours of illness. When you suspect bacterial or atypical pneumonia, base your choice of empiric antibiotic therapy on the most likely causative organisms.

Patients who are up to 6 months old need to be hospitalized and treated with IV antibiotics effective against the typical causative agents in this age group. Obtain blood samples for culture before you start therapy. If afebrile pneumonitis is likely, outpatient treatment with a macrolide is appropriate. Although there is an association between orally administered erythromycin and the development of pyloric stenosis in infants younger than 6 weeks, erythromycin is recommended in this age group for suspected Chlamydia infections. Be sure to warn parents of this possible association.  Data are scant concerning the safety and efficacy of the use of other macrolides (ie, azithromycin) in the young infant.²

The older infant, toddler, and school-aged child can be treated safely as an outpatient if he or she is immunocompetent, appears to be well, is able to stay adequately hydrated, and is not hypoxic. When viral pneumonia is likely, provide supportive care for the child. For the young child with suspected bacterial pneumonia, we recommend initial therapy with amoxicillin, amoxicillin/clavulanate, or cefuroxime. If resistant S pneumoniae is a major factor in your community, high-dose amoxicillin may be necessary.

Clindamycin is an alternative if a child with suspected pneumococcal infection is beta-lactam–allergic. A macrolide is another option; however, standard doses of azithromycin, for example, provide marginal beta-lactamase coverage. Although S pneumoniae is the most likely bacterial cause of pneumonia, antibiotics such as amoxicillin/clavulanate and cefuroxime allow for treatment of beta-lactamase–producing organisms (such as nontypeable H influenzae), which may be an increasing threat in this era of conjugate pneumococcal vaccine use.

Treat the older child and adolescent with a macrolide initially because atypical pathogens have a greater significance in this age group. Doxycycline may be used for children older than 8 years of age. If the child fails to respond, it is reasonable to add or switch to one of the previously mentioned antibiotics.
 
In certain situations, it may be necessary to treat for both bacterial and atypical pneumonia, with 2 agents-a beta-lactam and a macrolide or doxycycline. Fluoroquinolones are active against both S pneumoniae and organisms that cause atypical pneumonia; therefore, they may be used in adolescents with pneumonia. Antibiotics are usually prescribed for 7 to 10 days. If there is no response or if the patient’s health deteriorates, consider other organisms and change antibiotics accordingly.

The management of a complication of pneumonia depends on its severity; patients typically require hospitalization for close monitoring. Pneumonia with a small effusion can be successfully treated with antibiotics alone, but large parapneumonic effusions and empyemas often require drainage. Seek surgical consultation to determine the best course for each circumstance. Because the treatment of pneumonia is empiric, outpatients need to be reevaluated frequently to ensure adequate response. Hospitalization is necessary for the child whose health worsens despite optimal outpatient management.

FIGURE 2

COMPLICATIONS
Complications of pneumonia can be local and may occur secondary to the spread of pulmonary infections to contiguous structures (eg, pleural effusion and empyema, pericarditis, and worsening of pulmonary infection leading to formation of a pulmonary abscess) (Figure 2). Complications can also be systemic; they may arise secondary to bacteremia, which can cause meningitis, osteomyelitis, or septic arthritis.

Bacterial pneumonia is the most common cause of pleural effusion or empyema. Pleural effusion can be a part of the clinical spectrum of pneumonia as a synpneumonic effusion, or it may be a complication that leads to an accumulation of pus in the pleural cavity, resulting in an empyema. Patients often have signs and symptoms of pneumonia along with a characteristic pleural rub (especially in small pleural collections), worsening of fever, respiratory distress, decreased air entry on the affected side, dullness to percussion, and mediastinal shift to the opposite side if the fluid accumulation is rapid and significant. These complications are more common in patients with staphylococcal or streptococcal pneumonias and in those who use antibiotics inappropriately or incompletely.

Treatment of children with a complication includes ultrasonograms or chest CT scans for diagnosis, antibiotics based on sensitivity patterns, and thoracotomy with tube drainage. Most patients respond to these interventions and rarely require additional interventions such as injection of fibrinolytic agents into the pleural space.

References
1. Bradley JS, Byington CL, Shah SS, et al. 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;53:e25-e76.
2. Centers for Disease Control and Prevention.  Sexually Transmitted Diseases Treatment Guidelines,  2010- Chlamydia infections.  http://www.cdc.gov/std/treatment/2010/chlamydial-infections.htm
 

For More Information:

o Browne LR, Gorelick MH. Asthma and pneumonia. Pediatr Clin North Am. 2010;57:1347-1356.

o Pavia AT. Viral infections of the lower respiratory tract: old viruses, new viruses, and the role of diagnosis. Clin Infect Dis. 2011;52(Suppl 4):S284-289.

o Prayle A, Atkinson M, Smyth A. Pneumonia in the developed world. Paediatr Respir Rev. 2011;12:60-69. Epub 2010 Oct 14.

o Singh V, Aneja S. Pneumonia- management in the developing world. Paediatr Respir Rev. 2011;12:52-59. Epub 2010 Oct 16.http://www.ncbi.nlm.nih.gov/pubmed/21172676

o Spurling GK, Doust J, Del Mar CB, Eriksson L. Antibiotics for bronchiolitis in children. Cochrane Database Syst Rev. 2011 Jun 15;(6):CD005189.

o Webster J, Theodoratou E, Nair H, et al. An evaluation of emerging vaccines for childhood pneumococcal pneumonia. BMC Public Health. 2011; 11(Suppl 3):S26.