Invasiveness:
This
is the ability to enter host tissues, multiply there, and spread.
This in otherwise means, the organism will be able to bypass the
body’s defense system and if possible, enter immunity surveillance
free environments. Take an example of infection from Mycobacteria
tuberculosis, antaemeba histolytica.
Toxigenicity:
This is the ability to produce toxic substances to the human cells.
In this case, the chemicals produced by such organisms will not only
be strange and new to the host cell, but also dangerous or able to
cause toxicity. For example tetanus toxin produced by Clostridium
tetani. In
addition, microorganisms adopt many strategies to circumvent the
defenses of the host. Different microbes possess these attributes in
varying degrees depending on the specific strain. Most pathogens
have many such factors and although some have been identified, it is
still not known in all cases precisely how each factor functions in
the production of disease. The nature and mode of action of some of
the known virulence attributes in pathogenesis is described here.
Invasiveness
and
the role of Adhesin: Most
infections actually begin on the mucous membranes of the respiratory,
gastrointestinal or urogenital tracts. In these environments, the
potential pathogen must first adhere to the host cell. Adherence
prevents the microorganism from being flushed away in mucus
secretions and renders it less susceptible to the effects of enzymes
and secretory IgA. If
disease is to result from the effects of a toxin, close adherence of
the bacterium assures that the toxin will be delivered in high
concentrations directly to the host cell. Adherence must occur
before penetration of host cells (invasion) is possible for example
in case if HIV.
RELATED;
1. BACTERIOLOGY
2. VIROLOGY
3. IMMUNITY
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