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Colonization and Invasion by Bacterial Pathogens (page 1)
(This chapter has 4 pages)
© Kenneth Todar, PhD
Microbial pathogenicity has been defined as the structural
biochemical mechanisms whereby microorganisms cause disease.
in bacteria may be associated with unique structural components of the
cells (e.g. capsules, fimbriae, LPS or other cell wall components) or
secretion of substances that either damage host tissues or protect the
bacteria against host defenses. Hence, there are two broad qualities of
that underlie the means by which they cause disease:
invasiveness and toxigenesis.
Toxigenesis is the ability
produce toxins. Toxic substances produced by bacteria, both soluble
may be transported by blood and lymph and cause cytotoxic effects at
sites remote from the original point of invasion or growth.
Invasiveness is the ability
of a pathogen to
invade tissues. Invasiveness encompasses (1) mechanisms for
and initial multiplication), (2) production of extracellular substances
("invasins"), that promote the immediate invasion of tissues and (3)
ability to bypass or overcome host defense
mechanisms which facilitate the actual invasive process. This chapter
deals with the
first two aspects of of invasiveness: colonization and invasion.