《微生物学 Microbiology》课程PPT教学课件（英文版）microbial mechanisms of pathogenicity

Chapter 15 Microbial Mechanisms of Pathogenicity

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings B.E Pruitt & Jane J. Stein Chapter 15 Microbial Mechanisms of Pathogenicity

Microbial Mechanisms of Pathogenicity 。Pathogenicity The ability to cause disease ·Virulence The extent of pathogenicity

Microbial Mechanisms of Pathogenicity • Pathogenicity The ability to cause disease • Virulence The extent of pathogenicity

Portals of Entry ·Mucous membranes 。Skin ·Parenteral route

• Mucous membranes • Skin • Parenteral route Portals of Entry

Numbers of Invading Microbes ID50:Infectious dose for 50%of the test population 。 LD50:Lethal dose (of a toxin)for 50%of the test population

• ID50: Infectious dose for 50% of the test population • LD50: Lethal dose (of a toxin) for 50% of the test population Numbers of Invading Microbes

Bacillus anthracis Portal of entry 1D50 Skin 10-50 endospores Inhalation 10,000-20,000 endospores Ingestion 250,000-1,000,000 endospores

Bacillus anthracis Portal of entry ID50 Skin 10-50 endospores Inhalation 10,000-20,000 endospores Ingestion 250,000-1,000,000 endospores

Adherence Adhesions/ligands bind to receptors on host cells ·Glycocalyx Streptococcus mutans 。Fimbriae Escherichia coli 。M protein Streptococcus pyogenes 。Opa protein Neisseria gonorrhoeae 。Tapered end Treponema pallidum

• Adhesions/ligands bind to receptors on host cells • Glycocalyx Streptococcus mutans • Fimbriae Escherichia coli • M protein Streptococcus pyogenes • Opa protein Neisseria gonorrhoeae • Tapered end Treponema pallidum Adherence

Enzymes 。Coagulase Coagulate blood 。Kinases Digest fibrin clots 。Hyaluronidase Hydrolyses hyaluronic acid 。Collagenase Hydrolyzes collagen ·IgA proteases Destroy IgA antibodies ·Siderophores Take iron from host iron- binding proteins 。Antigenic variation Alter surface proteins

• Coagulase Coagulate blood • Kinases Digest fibrin clots • Hyaluronidase Hydrolyses hyaluronic acid • Collagenase Hydrolyzes collagen • IgA proteases Destroy IgA antibodies • Siderophores Take iron from host iron￾binding proteins • Antigenic variation Alter surface proteins Enzymes

Penetration into the Host Cell Figure 15.2

Penetration into the Host Cell Figure 15.2

Toxins 。Toxin Substances that contribute to pathogenicity 。Toxigenicity Ability to produce a toxin Toxemia Presence of toxin the host's blood 。Toxoid Inactivated toxin used in a vaccine 。 Antitoxin Antibodies against a specific toxin

Toxins • Toxin Substances that contribute to pathogenicity • Toxigenicity Ability to produce a toxin • Toxemia Presence of toxin the host's blood • Toxoid Inactivated toxin used in a vaccine • Antitoxin Antibodies against a specific toxin

Endotoxin Endotoxin (b)Endotoxins are part of the outer portion of the cell wall(lipid A;see Figure 4.12c)of gram-negative bacteria.They are liberated when the bacteria die and the cell wall breaks apart. Figure 15.4b

Endotoxin Figure 15.4b