Polysaccharide encapsulated bacteria

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SEM micrograph of an encapsulated bacteria (Pneumococcus).

Polysaccharide encapsulated bacteria, frequently referred to simply as encapsulated bacteria and less precisely called encapsulated organisms, are a group of bacteria that have an outer covering, a capsule, made of polysaccharide.

Examples of encapsulated bacteria

Role in disease

Many encapsulated bacteria are pathogens that lead to a significant amount of morbidity and mortality.[3]


People that lack a spleen, functionally (as in sickle cell disease[4][5]) or anatomically (due to a splenectomy or congenital absence), have been shown to be more susceptible to these pathogens. Therefore, it is standard medical practise to recommend vaccination.

People with asplenia are commonly offered vaccines against Neisseria meningitis, Haemophilus influenzae, and Streptococcus pneumoniae; these vaccines can be remembered with the mnemonic: NHS.


Young children do not have the ability to make antibodies to polysaccharide and are, therefore, more susceptible to encapsulated bacteria.[3]

See also


  1. 1.0 1.1 1.2 1.3 Jakobsen H, Jonsdottir I (2003). "Mucosal vaccination against encapsulated respiratory bacteria--new potentials for conjugate vaccines?". Scand J Immunol. 58 (2): 119–28. PMID 12869132.
  2. Lee CJ, Lee LH, Koizumi K. Polysaccharide Vaccines for Prevention of Encapsulated Bacterial Infections: Part 1. Infect Med 19(3):127-133, 2002. Partial Free Text.
  3. 3.0 3.1 Vinuesa C, de Lucas C, Cook M (2001). "Clinical implications of the specialised B cell response to polysaccharide encapsulated pathogens". Postgrad Med J. 77 (911): 562–9. PMID 11524513. Full Free Text.
  4. Pearson H. "Sickle cell anemia and severe infections due to encapsulated bacteria". J Infect Dis. 136 Suppl: S25–30. PMID 330779.
  5. Wong W, Powars D, Chan L, Hiti A, Johnson C, Overturf G (1992). "Polysaccharide encapsulated bacterial infection in sickle cell anemia: a thirty year epidemiologic experience". Am J Hematol. 39 (3): 176–82. PMID 1546714.