Question

MU DISCUSSION 1. What effect does the presence of a capsule have on pathogenicity! 2. Look up the definition for opsonin. How would opsonins affect the pathogenicity of a capsule 3. Define negative stain. 4. Define LPS.

Answer 1

1. capsule helps the bacteria to attach to the host organism. It is considered as a virulence factor because it enhances the ability of a bacteria to cause a disease and thereby preventing phagocytosis. Capsule protects the cells from engulfing by the eukaryotic cells eg- macrophages, and increases the tolerance of dissecation. It reduces the action of complement mediated killing and act as virulence deteminants.

2. Opsonin is an antibody that can bind to foreign cells and increase and makes them more susceptible to phagocytosis. Antibodies such as IgA, IgM, IgG can bind to capsules and block their attachment to host cells. IgG and IgM activates the classical complement mediated pathway. IgA and IgM clumps bacteria together by enabling them to be more fatsly removed by phagocytes. Moreover they combines with the exotoxin before they interact with the host and neutralizes toxin.

3. Staining the background of the slide is negative stain and actual specimen is untouched and thus visible. Its used for diagnostic microscopy for contrasting a thin specimen with an opaque fluid. Eg- Nigrosin

4. Lipopolysaccaride is the outer covering of gram negative bacteria. They are composed of lipids and polysaccharide composed of O-antigen and contributes to the structural integrity of bacteria. It increases the negative charge of cell memebrane and prevents the bacteria from chemical attacks.