Epidemiology and bacteriology of bacterial pneumonias.

An understanding of the epidemiology and bacteriology of pneumonia in childhood is frustrated by the difficulties in making an aetiological diagnosis in young children. Incidence figures for community-acquired pneumonia are derived from the 1970s and 1980s and suggest that the incidence is higher in young children than in older children: approximately 40/1000/year <5 years of age and 15/1000/year aged 5-14 years. Certain pathogens are associated with pneumonia in different age groups, Mycoplasma pneumoniae and Chlamydia pneumoniae are more commonly implicated in older age groups and viruses in younger age groups. The most common bacterium, Streptococcus pneumoniae is less influenced by age. The mortality from community-acquired pneumonia in developed countries appears to be very low. The range of potential bacterial pathogens associated with nosocomial pneumonia and with pneumonia in the immunosuppressed child is wider with Gram-negative aerobic bacilli the most frequent isolate.