Path Lab - Asplenia Flashcards
Most bacteria have an outer layer of polysaccharide. What are the 3 different layer types of polysaccharide?
a) glycocalyx – very thin layer
b) capsule – thicker layer
c) slime - Amorphous polysccharide extending into the environment
How is capsular serotyping done?
In a given species of encapsulated bacteria, there are generally a number of different antigenic types, determined by the type and the arrangement of the polysaccharides.
Specific antibodies raised in animals (eg. mice, rabbits) can be used in the serotyping of encapsulated bacteria by observing their agglutination when mixed with different antibodies (antisera).
How many capsular serotypes are there for Neisseria meningitidis?
13
How many capsular serotypes are there for Streptococcus pneumoniae?
90
How many capsular serotypes are there for Haemophilus influenzae?
6 encapsulated serotypes. Other non encapsulated serotypes exist
Name the serotypes for Neisseria meningitidis
A,B,C,D,E,W,X,Y,Z,H,I,K,L
Name the serotypes for Haemophilus influenzae
A-F
h serotypes of N. meningitidis cause most disease in Australia?
B and C. B accounts for most cases, and C accounts for about 1/3.
Which groups of people in the Australian population are most predisposed to serious infection with S. pneumoniae?
- Adults over 65
- children under 2
- immunocompromised people
Which serogroup of H. influenzae is the most virulent, and why is it now an uncommon pathogen in Australia?
- type B (Hib)
- Vaccinations
What categories of vaccines are there?
- Live (Attenuated) vaccines
- Inactivated vaccines – contain one or a few components of the organism, i.e. polysaccharide. It cannot replicate.
a) conjugated
b) non-conjugated
What vaccines are available in Australia for Neisseria meningitidis?
- meningococcal B vaccine Bexsero® available on private market
- meningococcal ACWY vaccine available on prescription for travellers
- Meningococcal C vaccination is recommended as part of routine childhood immunization – given at 12m
What vaccines are available in Australia for Streptococcus pneumonia?
Pneumococcal vaccine is recommended as part of routine childhood immunisation, – given at 2m, 4m, 6m. Booster at 12m and 4 years.
What vaccines are available in Australia for Haemophilus influenzae?
Hib vaccination is recommended as part of routine childhood immunization – 2,4,6 months. Booster at 12 months.
What are some of the functions of bacterial capsules?
- permeability barrier
- adherence to surfaces
- carbohydrate reserve for subsequent metabolism
- resistance to phagocytosis by cells of the immune system