Question

List the Mechanisms of Pathogenicity employed by disease causing microorganisms and give an example for each.

Answer 1

There are four types of pathogens.

virus ,fungi,bacteria  and parasites.

Pathogenecity means the ability of an organism to cause disease.The steps involved in pathogenesis are exposure,adhesion,invasion,infection and transmission.

Mechanism of action of viral pathogenecity

There are certain that contribute the pathogenecity of virus.It includes ability of the virus to enter the cell,ability of the virus to grow inside the cell,ability of defense mechanism,ability to make permanent or temporary damage to the cell through production of toxic substances,cell transformation and by induction of structural alterations in the host cells.

virus must enter into the host cell for the replication either in the mucousmembrane itself or in the tissues by penetration through the surface membrane.After penetration it will start multiplying by using the host cell materials.This is cell lysis.After cell replication many viral components are accumulate in the cell.They either multiply in a normal manner or they may be dormant in the cell and eventually transforms the cell in to a malignant cell.Example includes HIV virus

Mechanism of action of bacterial pathogenecity

Bacterial pathogenesis is the process by which bacteria infect and cause disease ina host . Microbes express the pathogenecity by means of their virulence.The determinants of virulance of a pathogen are any of its genetic r biochemical or structural features that enable to produce disease.The mechanism includes

a. Invasiveness is the ability to enter the tissue of host,

b.adherence and initial multiplication

c. production of extracellular substance to facilitate invasion

d . ability to overcome host defense mechanism.

Bacteria are much larger than virus.They enter host cell through phagocytosis.Phagocytosis is a normal function of macrophages.They patrol the tissues of the body and destroy unwanted tissues.

Example for bacterial pathogenecity is  E.Coli

Mechanism of action of pathogenecity of fungi

Fungi often develop both virulence mechanism and morphologic forms that facilitate within the host.Often fungal infections start in the lungs or in the skin as they are reproduce throgh tiny spores in the air.Fungal infections occur when an invading fungus takes over the part of a body and it is too much difficult for the immune system to handle.There are some fungi that lives naturally in the human body.Fungi enters the skin through tiny cracks in the body. Example -candida

Mechanism of action of pathogenecity in parasites

The pathogenic mechanism of parasites varies according to the species , quantity of parasites and by infective dose and virulence.There is huge variation across pathogens species in the number of cells required to infect a host.This number is known as infective dose.In pathogens where the molecules are secreated to facilitate infection acted locally,the number of cells required to start an infection ,ie,infective dose,was lower than in pathogens where the secreated molecules act more distantly. Example -fleas ,taoeworm