Pneumokokit

Pneumokokit, or pneumococci, are Gram-positive, lancet-shaped diplococci belonging to the species Streptococcus pneumoniae. They commonly reside in the human nasopharynx as part of the normal microbiota but can cause disease when they invade normally sterile sites.

The organism is encapsulated, and the capsule is a major virulence factor. More than 90 serotypes exist, defined by their capsule polysaccharides; vaccines target a subset of these serotypes. Pneumococci are spread through respiratory droplets, and carriage is more common in children and in settings with close contact. Carriage can be asymptomatic but may lead to invasive disease in susceptible individuals.

Clinical disease caused by pneumokokkit ranges from noninvasive to invasive. Noninvasive diseases include otitis media and sinusitis, especially in children. Pneumonia is a common pneumonia-causing agent in adults and children. Invasive pneumococcal disease includes meningitis, bacteremia, and sepsis, which can be life-threatening, particularly among the elderly and immunocompromised.

Diagnosis typically relies on culture from blood, cerebrospinal fluid, or other sterile sites, with additional support from urinary antigen testing or PCR. Imaging may aid in evaluating pneumonia. Treatment involves antibiotics, guided by local resistance patterns; resistance to penicillin and other drugs has emerged in certain strains, influencing empirical therapy choices.

Prevention focuses on vaccination and public health measures. Conjugate vaccines (such as PCV13, PCV15, PCV20) and the polysaccharide vaccine PPSV23 reduce carriage and disease and have substantially lowered invasive pneumococcal disease in many populations. Vaccination strategies aim to protect children and at-risk adults, contributing to herd immunity and reduced antibiotic use.