Pneumococcal

Pneumococcal refers to infections caused by the bacterium Streptococcus pneumoniae, a Gram-positive, encapsulated diplococcus that colonizes the human nasopharynx and can invade sterile sites. The organism is characterized by a polysaccharide capsule, which defines many serotypes and helps it resist phagocytosis. More than 90 serotypes have been described, which has implications for vaccine design and effectiveness.

Most commonly, pneumococcus spreads through respiratory droplets and colonization is more frequent in children. Invasive disease occurs when the bacteria enter sterile compartments such as the bloodstream or meninges, or when pneumonia extends into the pleura. Clinical manifestations include pneumococcal pneumonia (often with fever, cough, and chest pain), acute otitis media in children, sinusitis, meningitis, and bacteremia. Severe disease is more likely in the very young, the elderly, and individuals with certain chronic conditions or compromised immune systems.

Vaccination forms a central part of prevention. Pneumococcal conjugate vaccines (for example, PCV13, PCV15, and PCV20) target multiple serotypes and can reduce invasive disease and nasopharyngeal carriage in both vaccinated individuals and the broader community. Polysaccharide vaccines (such as PPSV23) cover additional serotypes and are recommended for older adults and certain risk groups. Serotype replacement can occur as vaccination shifts circulating strains.

Diagnosis relies on culture from blood or cerebrospinal fluid, with urinary antigen testing and molecular methods supporting rapid detection. Treatment depends on susceptibility and local guidelines, with awareness of rising penicillin and macrolide resistance in some regions.