Pneumococcus (Streptococcus pneumoniae) is a common cause of invasive bacterial infection in children and a frequent cause of community-acquired pneumonia [1,2]. Intermediate or high-level resistance to penicillin has become a significant problem. Children, particularly those in child care facilities and those receiving frequent courses of antibiotics, appear to be important carriers of resistant strains [3-5].
The clinical features, diagnosis, and treatment of pneumococcal pneumonia will be reviewed here. An overview of the clinical features and diagnosis of community-acquired pneumonia in children and the microbiology, pathogenesis, and epidemiology of S. pneumoniae are discussed separately. (See "Community-acquired pneumonia in children: Clinical features and diagnosis" and "Microbiology and pathogenesis of Streptococcus pneumoniae".)
The pneumococcus is acquired by aerosol or inhalation, leading to colonization of the nasopharynx; pneumococci are carried asymptomatically in approximately 50 percent of individuals at any point in time . In children, the incidence of pneumococcal carriage may be as high as 60 percent, even after immunization with the pneumococcal conjugate vaccine [7-9]. (See "Microbiology and pathogenesis of Streptococcus pneumoniae", section on 'Pathogenesis'.) Antibiotic-resistant strains are increasingly common . (See "Resistance of Streptococcus pneumoniae to beta-lactam antibiotics" and "Resistance of Streptococcus pneumoniae to the fluoroquinolones, doxycycline, and trimethoprim-sulfamethoxazole" and "Resistance of Streptococcus pneumoniae to the macrolides, azalides, lincosamines, and ketolides".)
Invasive disease most commonly occurs upon acquisition of a new serotype, typically after an incubation period of one to three days.
The incidence of disease increases strongly in association with a viral illness, such as influenza, parainfluenza, respiratory syncytial virus, adenovirus, or human metapneumovirus [11-14]. In a case-control study, upper respiratory infections with viruses such as influenza and parainfluenza correlated with acquisition of new serotypes of pneumococci in children . This association is believed to be related to increased expression of receptors for pneumococcal attachment on virally activated respiratory epithelial cells . In addition, viral neuraminidases cleave sialic acid from host cell glycoconjugates, and the resulting free sugar is used as a nutrient to increase the growth and density of pneumococci in the nasopharynx . This adds another dimension to the synergy between viruses and pneumococci in the pathogenesis of pneumonia.