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 bacterial capsule, made of polysaccharide.

A popular mnemonic to remember most of the encapsulated bacteria is the SHiNE SKiS bacteria (S. pneumo, Hib, N. meningitidis, E. Coli, Salmonella, Klebsiella, Group B Strep).

Many encapsulated bacteria are pathogens that lead to a significant amount of morbidity and mortality. The smooth surface and negative charge of the exterior capsule limits the ability of phagocytes to counteract the bacteria through cell-mediated immunity, and hence the humoral immune response of B cell antigens is important for the removal of encapsulated bacteria. Patients with B cell deficiencies are highly susceptible to encapsulated bacterial infections.

People that lack a spleen, functionally (as in sickle cell disease) or anatomically (due to a splenectomy or congenital absence, as in Ivemark Syndrome for example), have been shown to be more susceptible to these pathogens due to impaired opsonization of such organisms. Therefore, it is standard medical practice to recommend vaccination.

It is generally recommended that people with asplenia are vaccinated against Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae. These vaccines can be remembered with the mnemonic: SHiN. Alternatively they can be called the NHS bacteria, as in National Health Service in the UK.

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