Question

Describe the mechanism of pathogenesis of staphylococcus Aureus, and the implications of presence/absence of the pathogen in regards to risk to the consumer.

Answer 1

Answer: Staphylococcus aureus have different mode of pathogenesis. The basic mode of pathogenesis followed by all pathogen is following various steps as:

1.Enter to host cell

2.Attachment to host cell

3. Propagation with host cell

4. Intoxication or killing the host cell

5.Releasing by immune modification

But if we talk about staphylococcus aureus then it will follow certain modification to enter to host cell. It have two important features to enter the host cell:

1. Fight against immunity

2. Destroy host cell

Fight against immunity: For this process there is two type of modification

a) presence of surface molecule as protein A

b)Presence of FnBP(fibronectin binding protein)

The presence of this modification is that Protein A is actually helping Staphylococcus aureus to escape the immune system or escape the engulfing by macrophages as the tendency of protein A is to bind with FC portion of IgG molecule as a result of this it is escaped by endocytosis.

By the process of immunologic action it is clear that for the engulfment of bacteria it is need to be coated by antibody so that its Fab(antigen binding region) is to be attached directly with antigen so that macrophage can identify it and engulf it.But in the case of this Protein A is designated in such a way that it will bind by antigen not by Fab portion but by the FC region so it is not recognized as different by macrophages.

FnBP: This act as stabilizing molecule at a particular place so it is not providing any further signal as it is attached to fibronectin it will recognized as its own cell so our immune system getting confused as it is not getting signal that it is a pathogen.

2. Destruction of host cell: Destruction of host cell is largely caused by exotoxins as well as by various enzymes.

Generally the exotoxins are of two types which play part as:

a)Cytolytic toxin: Associated by red blood cells(RBC) so it is responsible for rapturing the RBC.

b) Immune toxin: It is going to force our immune cell to generate more and more chemical mediators as interlukins and cytokins as a result of this will cause Toxic sock syndrome(TSS).A s in case of staphylococcus aureus a different type of antigen is present called as immunotoxin or superantigen. This superantigen will fit in the place of foreign partical which is supposed to be antigen so it will activate more and more T cell synthesis by the secretion of cytokins and interlukins which will result in tissue damage.

b)Enzymes: various enzymes as catalase and coagulase are also secreated by this species which is associated to the lysis of fibrinectin hylorunic acid present in the skin cell which ultimately making the tissue lining thin.