Microbiology chapter 15

Question 1

pathogenicty vs virulence

Answer 1

Pathogenicity: the ability to cause disease
Virulence: the extent of pathogenicity

Question 2

pathogenicity steps

Answer 2

Entry
Attachment
Penetration
This may involve avoiding host defense mechanisms.
Host cell damage
Exit

Question 3

Portals of Entry

Answer 3

Portals of Entry
Mucous membranes
Skin
Parenteral route
A particular microorganism has a preferred portal of entry

Question 4

Numbers of Invading Microbes:

ID 50, LD 50

Answer 4

ID50: infectious dose for 50% of the test population
LD50: lethal dose (of a toxin) for 50% of the test population

Question 5

adherence is when Adhesins/ligands of microorganism bind to receptors on host cells, which cause?

Answer 5

Adherence allows for the formation of biofilms

Question 6

How Bacterial Pathogens Penetrate Host Defenses

Answer 6

capsules, cell wall components, enzymes

Question 7

Capsules penetrate by

Answer 7

Prevent phagocytosis
Streptococcus pneumoniae
Haemophilus influenzae
Bacillus anthracis
What else can the capsule do for “its” bacterium?

Question 8

cell wall components are used to?

Answer 8

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

Question 9

Enzymes are used to enter by

Answer 9

Coagulase: coagulates fibrinogen
Kinases: digest fibrin clots
Hyaluronidase: hydrolyzes hyaluronic acid
Collagenase: hydrolyzes collagen
IgA proteases: destroy IgA antibodies

Question 10

Penetration into the Host Cell Cytoskeleton

Answer 10

Invasins
Salmonella alters host actin to enter a host cell
Use actin to move from one cell to the next
Listeria
Salmonella entering intestinal epithelial cells as a result of ruffling

Question 11

Many vaccines provide years of protection against a disease. Why doesn’t the influenza vaccine offer more than a few months of protection?

Answer 11

antigenic variation

Question 12

How Bacterial Pathogens Damage Host Cells

Answer 12

Siderophores,Direct Damage,Toxins,Exotoxins

Question 13

Siderophores damage

Answer 13

Stealing nutrients from the host

Question 14

Direct Damage

Answer 14

Disrupt host cell function
Produce waste products
Toxins

Question 15

Toxins terminology: toxin, toxigenicty,toxemia,toxoid,antitoxin

Answer 15

Toxin: substance that contributes to pathogenicity
Toxigenicity: ability to produce a toxin
Toxemia: presence of toxin in the host’s blood
Toxoid: inactivated toxin used in a vaccine
Antitoxin: antibodies against a specific toxin

Many of these terms apply to exotoxins more than to endotoxins

Question 16

exotoxins

Answer 16

Exotoxins are proteins produced 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 17

endotoxins

Answer 17

Endotoxins are the lipid portions of lipopolysaccharides (LPS) that are part of the outer membrane of the cell wall of gram-negative bacteria (lipid A; see Figure 4.13c). The endotoxins are liberated when the bacteria die and the cell wall breaks apart

Question 18

Exotoxins work by

Answer 18

Specific for a structure or function in host cell
Mechanisms
A-B Toxins
Membrane-Disrupting Toxins
Superantigens

Question 19

Toxins-Membrane-Disrupting Exotoxins

Answer 19

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

Question 20

Toxins-Superantigen Exotoxins

Answer 20

Cause an intense immune response due to release of cytokines from host cells
Symptoms: fever, nausea, vomiting, diarrhea, shock, and death

Question 21

Endotoxins and the pyrogenic response

Answer 21

1.A macrophage ingests
a gram-negative bacterium.
2.The bacterium is
degraded in a vacuole, releasing endotoxins
that induce the macrophage to
produce cytokines IL-1 and TNF-.
3.The cytokines are
released into the bloodstream by the macrophages,
through which they travel to the hypothalamus of the brain.
4.The cytokines induce the hypothalamus to produce prostaglandins,
which reset the body’s
“thermostat” to a
higher temperature,
producing fever.

Question 22

Endotoxins-Limulus Amebocyte Lysate (LAL) Assay

Answer 22

Assay for presence of endotoxins
Mechanism
Amebocyte lysis produces a clot
Endotoxin causes lysis

Question 23

Food poisoning can be divided into two categories:

Answer 23

food infection and food intoxication. On the basis of toxin production by bacteria, explain the difference between these two categories.

Question 24

Viral Cytopathic Effects

Answer 24

No host cell macromolecule synthesis
Release of cellular enzymes from lysosomes
Inclusion bodies
Syncytium
Change in host cell function
Production of interferons
Antigenic change of host cell
Chromosomal changes
Contact inhibition

Question 25

Pathogenic Properties of Algae

Answer 25

Paralytic shellfish poisoning
Dinoflagellates
Saxitoxin
A neurotoxin

Question 26

Portals of Exit

Answer 26

Respiratory tract
Coughing and sneezing
Gastrointestinal tract
Feces and saliva
Genitourinary tract
Urine and vaginal secretions
Skin
Blood
Arthropods that bite; needles or syringes

Question 27

Microbial Mechanisms of Pathogenicity: factors

Answer 27

portals of entry, penetration of cells, host cell damage, portals of exit