Chapter 15 Flashcards by B Wade

Pathogenicity

The ability to cause disease

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Virulence

The degree of pathogenicity

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Portals of entry (name 3)

Mucous membranes - Skin - Parenteral route

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Parenteral route

Deposited directly into tissues when barriers are penetrated

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Most pathogens have a preferred _______ __ _____.

portal of entry

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ID₅₀

Infectious Dose for 50% of a sample population

Measures virulence of a microbe

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LD₅₀

Lethal Dose for 50 % of a sample population

Measures potency of a toxin

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Almost all pathogens attach to host tissues in a process called ________

adherence (adhesion)

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Adhesions (_____) on pathogen bind to _______ on host cells. Name two examples.

(ligands)

receptors

Glycocalyx
Fimbriae

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After adherence microbes form ______

biofilms

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Capsules: Glycocalyx around cell walls. What does this impair? Examples?

Impair phagocytosis

Streptococcus pneumoniae - pnuemonia

Haemophilus influenzae - pneumonia and meningitis

Bacillus anthracis - anthrax

Yersinia pestis - plague

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M protein

Cell wall component; resists phagocytosis

Example: streptococcus pyogenes

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Opa protein

Cell wall component; allows attachment to host cells

Example: neisseria gonorrhoeae

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Waxy lipid

Cell wall component; (mycolic acid) resists digestion

(mycobacterium tuberculosis)

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Coagulases

Coagulate fibrinogen

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Kinases

Digest fibrin clots

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Hyaluronidase

Digests polysaccharides that hold cells together

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Collagenase

Breaks down collagen

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IgA proteases

Destroy destroy IgA antibodies

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Antigenic Variation

Pathogens alter surface antigens (and antibodies are rendered ineffective)

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Invasions

Surface proteins produced by bacteria that rearrange actin filaments of the cytoskeleton (cause membrane ruffling)

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Pathogens use _______ to move from one cell to the next (shigella and lsiteria)

actin

_______ is required for most pathogenic bacteria

Siderophores

Proteins secreted by pathogens that bind iron more tightly than host cells

How does **direct damage** work?

* Disrupts host cell function * Uses host cell nutrients * Produces waste products * Multiplies in host cells and causes ruptures

Toxins

Poisonous substances produced by microorganisms Produce fever cardiovascular problems, diarrhea, and shock

Toxigenicity

Ability of microorganism to produce a toxin

Toxemia

Presence of toxi in host's blood

Intoxications

Presence of toxin without microbial growth

Exotoxins

Proteins produced and secreted by bacteria -Soluble in bodily fluids; destroy host cells and inhibit metabolic functions

Antitoxins

Antibodies against specific exotoxins

Toxoids

Inactivated exotoxins used in vaccines

A-B toxins

**Exotoxin** contain an enzyme component (A part) and binding component (B part) (diphteria toxin)

**Membrane-disrupting toxins** Name 3

* lyse host cells by disrupting plasma membranes 1. Leukocidins 2. Hemolysins 3. Streptolysins

Leukocidin Endo or Exo toxin?

Kill phagocytic leukocytes; Exotoxin

Hemolysis Endo or Exo -toxin?

Kills erythrocytes by forming protein channels; Exotoxin

Streptolysins Endo or Exo -toxin?

hemolysins produced by streptococci; Exotoxin

Superantigens Symptoms?

Cause intense immune response due to release of cytokines from host cells (T cells) Causes symptoms of fever, nausea, vomiting, diarrhea, shock, and death

Genotoxins

Damage DNA (causing mutations, disrupting cell division, and leading to cancer)

Lipid A Endo or Exo -toxin?

Portion of lipopolysaccharides (LPS) of gram-negative bacteria

What is released during bacterial multiplication and when gram-negative bacteria die?

Endotoxins - Stimulate macrophages to release cytokines - Cause disseminated intravascular coagulation

What may carry genes for toxins, production of antibiotics, and enzymes?

Plasmids

Lysogenic conversion

Changes characteristics of a microbe due to incorporation of a prophage

Cytopathic Effects (CPE)

Visible effects of a viral infection on a cell

Examples of CPEs?

* Stopping cell synthesis * Causing cell lysosomes to release enzymes * Creating inclusion bodies in the cell cytoplasm * Fusing cells to create syncytium * Changing host cell function or inducing chromosomal changes * Inducing antigenic changes on the cell surface * Loss of contact inhibition in the cell, leading to cancer * Producing interferons to protect uninfected cells

How do Fungi act as a pathogen?

* Toxic metabolic products * Provoke an allergic response * Trichothecene toxins inhibit protein synthesis * Proteases modify host cell membranes * Capsules prevent phagocytosis

Three main types of 'pathogenic' fungi

* Ergot * Aflatoxin * Mycotoxins

Ergot

Alkaloid toxins that cause hallucinations

Aflatoxin

Carcinogenic toxin produced by aspergillus

Mycotoxins Name two

Produced by mushrooms and are neurotoxic Phalloidin and Amanitin

Protoza avoid host defenses by what 3 methods?

Digesting cells and tissue fluids Grow in phagocytes Antigenic variation

Portals of Exit

* Respiratory tract * Coughing and sneezing * Gastrointestinal tract * Feces and saliva * Genitourinary tract * Urine; secretions from teh penis and vagina * Skin * Blood * Anthropods that bite; needles or syringes