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Mechanisms of Pathogenicit1

Mechanisms of Pathogenicit1 - = Leukocidins produced by...

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Mechanisms of Pathogenicity - Invasion, virulence factors, damage to host cells Pathogenic microorganisms employ a variety of virulence factors that contribute to their ability to evade host defenses and penetrate tissues - Many pathogenic bacteria possess capsules = Possession of a capsule seems to interfere with phagocytosis of the pathogen by white blood cells = In some cases, it has been shown that mutations that cause loss of the ability of to produce a capsule is associated with a loss of virulence (recall the experiments of Griffith) - Cell wall components can contribute to virulence = Pathogenicity of Streptococcus pyogenes, the agent of "strep throat" is associated with an M protein found on the cell surface = Cell wall components can interfere with host defenses; for instance the mycolic acids that make Mycobacterium species "acid-fast" may also prevent their destruction - The virulence of some bacteria is thought to be aided by production of extracellular enzymes
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Unformatted text preview: = Leukocidins, produced by species of Staphylococcus and Streptococcus, can cause destruction of white blood cells = Hemolysins cause lysis of red blood cells = Coagulases, which promote clot formation, may aid pathogenicity by isolating the pathogen from host defenses = On the other hand, streptokinase, produced by some Streptococcus strains, may contribute to virulence by causing clots to break down, releasing the pathogen from isolation = Hyalurinidase breaks down hyaluronic acid, a polysaccharide that helps to hold together connective tissues, helping the pathogen to spread within tissues = Collagenase breaks down collagen, a protein of connective tissue- Many “extracellular” bacteria have been shown to enter host cells through the activity of surface protein invasins (Tortora et al. Figure 15.2)...
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