The Determinants of Microbial Pathogenicity,
BIRMINGHAM UNIV (ENGLAND) DEPT OF MICROBIOLOGY
Pagination or Media Count:
The terms of pathogenicity and virulence are synonymous they mean the capacity to produce disease. To be pathogenic a microorganism must be able to 1 Infect the mucous surfaces of the respiratory, alimentary or urogenital tracts. Some microbes are introduced into the host directly through the skin by trauma or vector bite but the majority of infections start on the mucous surfaces. 2 Enter the host usually by penetration of the mucous surfaces. A few microbes can cause disease by growing on the mucous surfaces, for example cholera bacilli, but the majority enter the tissues to cause disease. 3 Multiply in the environment of the hosts tissues. 4 Resist or interfere with host defence mechanisms that try to remove or destroy them. 5 Cause damage to the tissues of the host. All five steps, or the last three if there is direct introduction into the tissues, must be accomplished for pathogenicity. Loss of ability to carry out any one of the steps causes the microbe to lose virulence. The cardinal fact about pathogenicity is its multifactorial nature.
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