Microbial Mecanisms Of Pathogenicity

Question 1

Pathogenicity

Answer 1

The ability to cause disease

Question 2

Virulence

Answer 2

The extent of pathogenicity

Question 3

What factors make a microbe a successful pathogen?

Answer 3

if it has the ability to enter and infect a host’s cells, cause damage to the host,
spread from one host to another,
adapt to changing environments and host immune systems,
persist in the environment or host tissues,
and have a broad host range or be specific to a particular host.

Question 4

Portals of entry:

Answer 4

Mucous membranes
Skin
Parenteral route
Preferred portal of entry

Question 5

Numbers of invading microbes:
ID50:

Answer 5

infectious dose for 50% of the test population

Question 6

Number of invading microbes
LD50:

Answer 6

lethal dose (of a toxin) for 50% of the test population

Question 7

Relative virulence of toxin

Answer 7

Question 8

Adhesins/ligands bind to

Answer 8

Receptors on host cells
Glycocalyx: Streptococcus mutans
Fimbriae: Escherichia coli
M protein: Streptococcus pyogenes
Form biofilms

Question 9

Capsules

Answer 9

Prevent phagocytosis
Streptococcus pneumoniae
Haemophilus influenzae
Bacillus anthracis

Question 10

Cell Wall Components

Answer 10

M protein resists phagocytosis
Streptococcus pyogenes
Opa protein inhibits T helper cells Neisseria gonorrhoeae
Mycolic acid (waxy lipid) resists digestion Mycobacterium tuberculosis

Question 11

Coagulase

Answer 11

Coagulates fibrinogen

Question 12

Kinases

Answer 12

Digest fibrin clots

Question 13

Hyaluronidase

Answer 13

Hydrolyzes hyaluronic acid

Question 14

Collagenase

Answer 14

Hydrolyzes collagen

Question 15

IgA proteases:

Answer 15

Destroy IgA antibodies (found in mucous membranes)

Question 16

Using the Host’s Nutrients: Siderophores

Answer 16

Use host’s iron

Question 17

Direct damage

Answer 17

● Disrupt host cell function
● Produce waste products
● Toxins

Question 18

Toxin

Answer 18

substance that contributes to pathogenicity

Question 19

Toxigenicity

Answer 19

ability to produce a toxin

Question 20

Toxemia

Answer 20

presence of toxin in the host’s blood

Question 21

Toxoid

Answer 21

inactivated toxin used in a vaccine

Question 22

Antitoxin

Answer 22

antibodies against a specific toxin

Question 23

Exotoxins

Answer 23

Specific for a structure or function in host cell

Question 24

Membrane-disrupting toxins

Answer 24

Lyse host’s cells by
Making protein channels in the plasma
membrane
Disrupting phospholipid bilayer

Question 25

Leukocidins

Answer 25

Destroys leukocytes

Question 26

Hemolysins

Answer 26

Destroys RBCs

Question 27

Streptolysins

Answer 27

Destroys immune cells

Question 28

Superantigens are usually an:

Answer 28

Exotoxin or other bacterial protein

Question 29

Superantigens cause an:

Answer 29

Intense immune response due to release of excessive amounts of cytokines from host cells

Question 30

Cytokines is a general term for:

Answer 30

cell communication and immune mediator chemicals (protein)

Question 31

Superantigens symptoms of intense immune response:

Answer 31

fever, nausea, vomiting, diarrhea, shock, and death

Question 32

Exotoxin sources

Answer 32

Question 33

Exotoxins and lysogenic (virus stays dormant in cells) conversion

Answer 33

Question 34

Endotoxins = only one type:

Answer 34

Lipid A released from dead Gram negative bacteria Lipopolysaccharide membrane

Question 35

Exotoxins are proteins produced:

Answer 35

Inside pathogenic bacteria, most commonly gram-positive bacteria, as part of their growth and metabolism. The exotoxins are then secreted into the surrounding medium during log phase.

Question 36

Exotoxin is a Ex(s)?

Answer 36

toxic substance released outside the cell Clostridium botulinum, an example of a gram positive bacterium that produces exotoxins

Question 37

Endotoxins are the

Answer 37

Lipid portions of lipopolysaccharides (LPS) that are part of the outer membrane of the cell wall of gram-negative bacteria. The endotoxins are liberated when the bacteria die and the cell wall breaks apart.

Question 38

Endotoxins are a Ex(s)?

Answer 38

Toxin composed of lipids that are part of the outer membrane Ex: Salmonella typhimurium, an example of a gram-negative bacterium that produces endotoxins

Question 39

Endotoxin and Fever (pyrogenic response) A macrophage ingests:

Answer 39

a gram-negative bacterium.

Question 40

Endotoxin and Fever (pyrogenic response) The bacterium is digested in a

Answer 40

phagosome, releasing endotoxins that induce the macrophage to produce cytokines IL-1 and TNF-

Question 41

Endotoxin and Fever (pyrogenic response) The cytokines reach the

Answer 41

hypothalamus causing it to produce prostaglandins, which reset the body’s “thermostat” to a higher temperature, producing fever.

Question 42

Endotoxin and Fever (pyrogenic response) As long as cytokines remain in the blood:

Answer 42

temperature remains high. When cytokines are gone body temp will go back to normal

Question 43

Endotoxins and the pyrogenic response (4 steps)

Answer 43

Question 44

Cytopathic Effects of Viruses

Answer 44

● Cell lysis ● Inclusion bodies (what’s left behind) ● Stop macromolecular synthesis in host cell ● Cause cell fusion (syncytium) ● Interfere with cell functions ● Cause antigenic changes on host cell surface leading to cell being destroyed by the immune system ● Chromosomal changes (possibly activation of oncogenes) ● Transformation of host cells- loss of contact inhibition leading to unregulated cell growth

Question 45

Pathogenic Properties of Fungi

Answer 45

-Fungal waste products may cause symptoms -Chronic infections provoke an allergic response -Trichothecene toxins inhibit protein synthesis :Fusarium -Proteases:Candida, Trichophyton -Capsule prevents phagocytosis: Cryptococcus ● Ergot toxin: Claviceps ● Aflatoxin: Aspergillus ● Mycotoxins: Neurotoxins: phalloidin, amanitin

Question 46

Pathogenic Properties of Protozoa

Answer 46

Presence of protozoa Protozoan waste products may cause symptoms Avoid host defenses by Growing in phagocytes Antigenic variation

Question 47

Pathogenic Properties of Helminths

Answer 47

-Use host tissue ● Presence of parasite interferes with host function ● Parasite’s metabolic waste can cause symptoms

Question 48

Pathogenic Properties of Algae

Answer 48

Paralytic shellfish poisoning -Dinoflagellates -Saxitoxin Red tide: more algae than normal (irritating to skin)

Question 49

Pathogenic Properties of Algae Portals of Exit:

Answer 49

-Respiratory tract: Coughing and sneezing Gastrointestinal tract: Feces and saliva Genitourinary tract: Urine and secretions -Skin -Blood: Arthropods that suck blood; needles or syringes

Question 50

Mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host’s defenses:

Answer 50

PORTALS OF ENTRY: Mucous membranes • Respiratory tract • Gastrointestinal tract • Genitourinary tract • Conjunctiva Skin Parenteral route

Question 51

Mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host’s defenses:

Answer 51

PENETRATION OR EVASION OF HOST DEFENSES: Capsules Cell wall components Enzymes Antigenic variation Invasins Intracellular growth

Question 52

Mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host’s defenses:

Answer 52

DAMAGE TO HOST CELLS: Siderophores Direct damage Toxins: • Exotoxins • Endotoxins Lysogenic conversion Cytopathic effects

Question 53

Mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host’s defenses:

Answer 53

PORTALS OF EXIT: Generally the same as the portals of entry for a given microbe: • Mucous membranes • Skin • Parenteral route