Pneumococcal pneumonia is a common lung infection caused by the organism Streptococcus pneumoniae (a.k.a. pneumococcus).
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Epidemiology
Pneumococcus accounted for around 95% of pneumonia cases in the pre-antibiotic, pre-vaccination era. Conjugate vaccinations were introduced in 2000. These protect children and give long-lasting protection to the elderly. Pneumococcal pneumonia now accounts for an estimated 27% of community-acquired pneumonia (CAP) globally. Africa and the Indian sub-continent have the highest rates of infection. Invasive pneumococcal disease (IPD) is predominantly a disease of children below the age of 2, causing around 11% of deaths from all causes.
In older age-groups, pneumonia accounts for 89% of deaths due to pneumococcus; meningitis and other IPDs for the remaining 11%. HIV and asplenia are major risk factors for pneumococcal disease. Other risk-factors include age over 65, COPD, asthma, alcohol abuse and various co-morbidities.
The reservoir for infection is the human nasopharynx which is typically colonized by age 5. Children are renowned for their ability as spreaders! Vaccination is effective against carriage, however other serotypes replace the eliminated strains and new strains emerge. Current developments are focused towards serotype-independent vaccination 6,7.
Clinical presentation
The clinical presentation of pneumococcal pneumonia includes fever, cough and malaise and may also include chest pain and dyspnea or tachypnea.
Pathology
Streptococcus pneumoniae is a Gram positive diplococcus. Over 100 serotypes are recognized and vaccination is available for the more virulent strains.
Asymptomatic nasopharyngeal colonization is common and usually occurs in childhood making children the main reservoir of infection. Transmission is by respiratory droplet from patients or carriers. Disease is either due to non-invasive contiguous spread to the middle ear, paranasal sinuses or lungs or invasive (IPD), with bacteremia which may cause seeding of sterile sites e.g. meninges.
Radiographic features
Radiographic appearances considered classic for pneumococcal pneumonia include lobar consolidations and air bronchograms in adults and round pneumonia in children, however this type of pneumonia can have many different appearances 1,2. CT may reveal lymphadenopathy and complications 5.
History
Pneumococcus was first recognized as the cause of pneumonia in the 1880s and experimental innoculation with killed bacteria began in the same decade.
Penicillin became available in 1940 and was regarded as a miracle cure, however antibiotic resistance was noticed in that same year.
Following a 25-year hiatus, new vaccines were introduced from the late 1970s. Conjugate vaccines, introduced in 2000 provoke stronger immunity and offer protection to children.