Name three organisms in which the presence of a capsule is important in their vi

Question

Name three organisms in which the presence of a capsule is important in their virulence and the disease(s) each causes. Identify the organisms in which the cell wall components discussed are important virulence factors. For each of the five enzymes listed tell which group of organisms is most likely to produce that enzyme. What advantages does production of these enzymes give to the organism that produces it and what are some of the diseases that result. What groups of organisms are most like to "change their coat" to evade antibodies of the immune system.

Explanation / Answer

3)

   i) Streptococcus pneumoniae (organism) - Streptococcal Pneumonia (disease caused)

The primary virulence factor of S. pneumoniae is its capsular polysaccharide. The capsular polysaccharide is composed of hyaluronic acid. It is the production of large amounts of hyaluronic capsular polysaccharide that plays an important role in protecting the organism from ingestion and killing by phagocytes .The pathogenesis is due to the rapid multiplication of the bacteria in alveolar spaces. The bacteria also produce the toxin pneumolysin that destroys host cells.   

ii)Haemophilus influenzae -  bacterial meningitis, bacteremia, pneumonia, epiglottitis .

The capsular polysaccharide of Haemophilus influenzae serotype b [(3)-beta-D-ribose-(1-1)-ribitol-5-phosphate] is a major virulence factor in these diseases .It is a target for serum antibodies which protect individuals against invasive infections.

iii)Neisseria meningitidis - meningitis and other meningococcal diseases

Neisseria meningitidis strains are frequently encapsulated and 13 different capsular serogroups have been found so far. These capsular polysaccharides protect the meningococci from the action of phagocytic cells and enhance organism’s survival during bloodstream and Central Nervous system invasion.

4) The names of the cell wall components have not been listed. Insufficient information

5) Enzymes not listed . Insufficient information

6) Oragnisms which change their coat to evade antibodies of the immune system employ antigenic variation. Antigenic variation can be found in :-

1 Bacteria- Neisseria meningitidis , Neisseria gonorrhoeae, species of the genus Streptococcus and Mycoplasma.
2 Protozoa- eg, Trypanosoma brucei , Plasmodium falciparum
3 Viruses- eg, Influenza virus, HIV1 VIRUS

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