Polysaccharide encapsulated bacteria


Polysaccharide encapsulated bacteria

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

*Haemophilus influenzae type B (Hib)cite journal |author=Jakobsen H, Jonsdottir I |title=Mucosal vaccination against encapsulated respiratory bacteria--new potentials for conjugate vaccines? |journal=Scand J Immunol |volume=58 |issue=2 |pages=119–28 |year=2003 |pmid=12869132 |doi=10.1046/j.1365-3083.2003.01292.x]
*Streptococcus pneumoniae (pneumococcus)
*Neisseria meningitides (meningococcus)
*Group B streptococcus (GBS)
*Salmonella typhiLee CJ, Lee LH, Koizumi K. Polysaccharide Vaccines for Prevention of Encapsulated Bacterial Infections: Part 1. Infect Med 19(3):127-133, 2002. [http://www.medscape.com/viewarticle/431127 Partial Free Text] .]

Role in disease

Many encapsulated bacteria are pathogens that lead to a significant amount of morbidity and mortality.cite journal |author=Vinuesa C, de Lucas C, Cook M |title=Clinical implications of the specialised B cell response to polysaccharide encapsulated pathogens |journal=Postgrad Med J |volume=77 |issue=911 |pages=562–9 |year=2001 |pmid=11524513 |doi=10.1136/pmj.77.911.562 [http://pmj.bmj.com/cgi/reprint/77/911/562.pdf Full Free Text] .]

Asplenia

People that lack a spleen, functionally (as in sickle cell disease [cite journal |author=Pearson H |title=Sickle cell anemia and severe infections due to encapsulated bacteria |journal=J Infect Dis |volume=136 Suppl |issue= |pages=S25–30 |year= |pmid=330779] [cite journal |author=Wong W, Powars D, Chan L, Hiti A, Johnson C, Overturf G |title=Polysaccharide encapsulated bacterial infection in sickle cell anemia: a thirty year epidemiologic experience |journal=Am J Hematol |volume=39 |issue=3 |pages=176–82 |year=1992 |pmid=1546714 |doi=10.1002/ajh.2830390305] ) 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".

Children

Young children do not have the ability to make antibodies to polysaccharide and are, therefore, more susceptible to encapsulated bacteria.This is especially so for children between 6months and 1year old,where maternalantibodies are depleted and endogeneous synthesis is not perfected yet.

ee also

*Conjugate vaccine

References


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