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Worldwide, community-acquired pneumonia is a leading cause of
infectious morbidity and mortality in children.1Studies
that employ blood culture, serology, and polymerase chain reaction,
as well as those that use pneumococcal conjugate vaccines as a probe
to determine the proportion of disease due to Streptococcus
pneumoniae, suggest that pneumococcus is the major pathogen
in community-acquired pneumonia in children, frequently in the presence
of concurrent viral respiratory infection. Several observations
such as the presence of patchy perihilar infiltrates
on x-ray suggests that most cases of bacterial pneumonia result
from aspiration of nasopharyngeal organisms and provide the rationale
that respiratory tract flora, nontypeable Haemophilus influenzae,
Streptococcus pyogenes, Moraxella catahhralis, Staphylococcus aureus, and S pneumoniae are
the major bacterial pathogens in pediatric pneumonia.
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Community-acquired pneumonia is most common in infants and toddlers.
In children ages 6 months to 5 years, the incidence is 40/1000
patients/year with declining frequency with increasing
age.2 Further analysis of the incidence of pneumonia
in children < 5 years of age identifies a peak incidence of 52.3/1000
children/year at 2 to 5 years of age with slightly lower
incidence rates in children < 24 months.3 Mortality due
to community-acquired pneumonia is low—0.1/1000
patients/year in children aged < 15 years. Males are
affected almost twice as commonly as females.4 Socioeconomic
status and ethnicity affect pneumococcal pneumonia rates, with a
greater risk of pneumonia in US children aged < 5 years of Asian,
African American, or Hispanic ethnicity compared with those of Caucasian
ethnicity.3 Seasonal variations show a greater
frequency in the winter and spring months,2,6,7 and
during peaks of respiratory syncytial virus (RSV), influenza A,
and, in older children, Mycoplasma pneumoniae.2 Mortality
due to community-acquired pneumonia, as reported from Finland, is
low—0.1/1000 patients/year in children
aged < 15 years. Gender differences are also observed, with males
having a rate nearly double that of females (47.4 vs 23.6/1000
patients/year in Finland).4 Differences
in incidence are also reported by socioeconomic status and ethnicity.
Rates of pneumococcal pneumonia are higher in native Alaskan children
than in nonnatives.5A greater risk of pneumonia
in US children aged < 5 years of Asian, African American, or
Hispanic ethnicity compared with those of Caucasian ethnicity has
also been observed.3 The incidence of community-acquired
pneumonia also varies by season; studies in the United States2,6 and
Israel7 report greater frequency in the winter
and spring months. Annual peaks of respiratory syncytial virus (RSV),
influenza A, and, in older children, Mycoplasma pneumoniae,
infection also are associated with higher pneumonia incidences.2Hospitalization
for all cause community-acquired pneumonia is greatest in children
less than 2 years of age and represents about 10% of all
pneumonia cases in that age group.8
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Lower respiratory tract infections (RTIs) are both more frequent
and associated with a greater mortality in developing countries.
The incidence among children ages 0 to 5 years from 10 developing
countries is estimated to range from 0.2 to 8.1 new episodes/100 child-weeks
at risk.9 Mortality from pneumonia has become uncommon
in developed countries,4,10,11 yet remains a major
cause of death in developing countries.12 In 1990,
respiratory infections were the third most common cause of death
worldwide; 90 percent of deaths occurred in developing countries.12 Nearly
70% of deaths are in children less than 4 years old.
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Microbiological Etiology
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Community-Acquired
Pneumonia
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A large spectrum of pathogens have the ...