[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Streptococci and enterococci](https://durgical.com/en/microbiology/groups/streptococci-and-enterococci/) › Streptococcus pneumoniae [Microbiology](https://durgical.com/en/microbiology/) · [Streptococci and enterococci](https://durgical.com/en/microbiology/groups/streptococci-and-enterococci/) # Streptococcus pneumoniae - Bacterium - Gram-positive - Exam priority: high A nose and throat bacterium behind most community pneumonia, ear infections, sinusitis and meningitis; a vaccine is in Colombia's PAI. Updated 2026-11-01 Also called: pneumococcus ## Key points - Lancet-shaped Gram-positive diplococcus, alpha-haemolytic. - Optochin sensitive and bile soluble (viridans: resistant and insoluble). - Capsule = virulence; asplenia and sickle cell disease raise the risk. - Leading cause of community pneumonia, otitis media and adult meningitis. - Penicillin resistance through altered PBPs, not beta-lactamase. ## At a glance **Gram** Gram-positive **Shape** Lancet-shaped diplococci **Oxygen** Facultative anaerobe **Family** Streptococcaceae **Stain** Gram positive; catalase negative; alpha-haemolytic ## Morphology - Lancet-shaped Gram-positive diplococci - Alpha (green) haemolysis on blood agar - Polysaccharide capsule; more than 100 serotypes ## Transmission - Contact with respiratory secretions (saliva, mucus) - Respiratory droplets from healthy carriers - Nasopharyngeal colonisation, especially in children ### Isolation precautions What the care team adds to standard precautions. - Standard ## Virulence factors - Polysaccharide capsule: the main antiphagocytic factor and the basis of vaccines - IgA protease: degrades mucosal IgA - Pneumolysin: damages cells and activates complement - Autolysin: releases inflammatory cell-wall pieces ## Diseases it causes - Community-acquired pneumonia (most common bacterial cause) [Community-acquired pneumonia →](https://durgical.com/en/conditions/community-acquired-pneumonia/) - Bacterial meningitis in adults and children [Bacterial meningitis →](https://durgical.com/en/conditions/bacterial-meningitis/) - Acute otitis media [Acute otitis media →](https://durgical.com/en/conditions/acute-otitis-media/) - Acute sinusitis [Acute rhinosinusitis →](https://durgical.com/en/conditions/acute-rhinosinusitis/) ## Clinical picture - Sudden high fever, rigors, cough with rusty sputum and pleuritic pain - Lobar consolidation on chest X-ray - Higher risk with asplenia, sickle cell disease, HIV, the extremes of age and alcohol use ## Diagnosis - Sputum Gram stain: lancet-shaped Gram-positive diplococci - Optochin sensitive and bile soluble - Quellung reaction (capsule swelling with antiserum) - Urinary C-polysaccharide antigen - Blood and cerebrospinal fluid cultures ## Treatment Beta-lactams (amoxicillin, ceftriaxone) are the mainstay. Some strains carry altered PBPs that lower penicillin susceptibility; in meningitis ceftriaxone is combined with vancomycin until susceptibility is known. Macrolide resistance is common. Drug class only; doses and regimens are set by the clinician from the current guideline. In Pharmacology: - [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/) - [Amoxicillin](https://durgical.com/en/pharmacology/amoxicillin/) - [Ceftriaxone](https://durgical.com/en/pharmacology/ceftriaxone/) - [Vancomycin](https://durgical.com/en/pharmacology/vancomycin/) ## Prevention - Conjugate vaccine in infants - Vaccination of older adults and people with risk factors - Hand and cough hygiene **Vaccine:** The pneumococcal conjugate vaccine (13-valent) is part of Colombia's PAI schedule for infants; vaccines also exist for older adults and risk groups. ## In Colombia Bacterial meningitis, pneumococcal included, is a notifiable surveillance event in Colombia; the conjugate vaccine is in the free PAI schedule. ## Memory aid Pneumococcus travels as a pair in a cloak: the capsule hides it, and the spleen is the bouncer that throws it out. ## Test yourself Think of the answer, then tap the question to see it. ## Which two tests distinguish pneumococcus from viridans streptococci? Optochin (pneumococcus sensitive) and bile solubility (pneumococcus soluble). ## Why do people without a spleen get severe pneumococcal disease? The spleen is key to clearing opsonised encapsulated bacteria; without it, pneumococcus spreads. ## What is the mechanism of pneumococcal penicillin resistance? Altered penicillin-binding proteins (PBPs) with lower affinity; it does not make beta-lactamase. ## Which isolation precautions does a patient with pneumococcal pneumonia need? Standard precautions only; droplet isolation is not required. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/streptococcus-pneumoniae/) ## Related - [Viridans streptococci](https://durgical.com/en/microbiology/viridans-streptococci/) - [Listeria monocytogenes](https://durgical.com/en/microbiology/listeria-monocytogenes/) ## Related conditions - [Community-acquired pneumonia](https://durgical.com/en/conditions/community-acquired-pneumonia/) - [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/) - [Acute otitis media](https://durgical.com/en/conditions/acute-otitis-media/) - [Acute rhinosinusitis](https://durgical.com/en/conditions/acute-rhinosinusitis/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. [← Back to the group: Streptococci and enterococci](https://durgical.com/en/microbiology/groups/streptococci-and-enterococci/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [About Pneumococcal Disease](https://www.cdc.gov/pneumococcal/about/index.html) (CDC, 2024); [Clinical Overview of Pneumococcal Disease](https://www.cdc.gov/pneumococcal/hcp/clinical-overview/index.html) (CDC, 2026); [Acortamiento del Esquema](https://www.minsalud.gov.co/sites/rid/Lists/BibliotecaDigital/RIDE/VS/PP/PAI/infografia-acortamiento-esquema-2025.pdf) (Ministerio de Salud y Protección Social, Colombia, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/streptococcus-pneumoniae/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/streptococcus-pneumoniae/