Chapter 15

Question 1

Pathogenicity

Answer 1

the ability to cause disease

Question 2

virulence

Answer 2

the extent of pathogenicity

Question 3

portals of entry

Answer 3

mucous membrane
  -gastrointestinal tract 
  -respiratory tract 
  - genitourinary tract 
skin
parenteral route

Question 4

preferred portal of entry

Answer 4

organisms can enter more than one way but many do not cause disease unless they enter the preferred portal of entry

Question 5

numbers of invading microbes

Answer 5

• ID50- infectious dose of 50% of test population
• LD50- lethal dose (of a toxin) for 50% of the test population
• wide variation from one kind of pathogen to another

Question 6

Bacillus Anthracis

Answer 6

portal of enter

• skin- (ID50)- 10-50 endospores
• inhalation (ID50)- 10,000-20,000 endospores
• ingestion (ID50)- 250,000-1,000,000 endospores

Question 7

Adherence/ ligands

Answer 7

• bind to receptors on host cells
• attachment is necessary step in pathogenicity; non-pathogens can have attachment molecules
• adhesions located on cells glycocalyx, pili, fimbriae or flagella
• adhesions made of glycoproteins and lipoproteins
• receptors on host cells are usually sugars

Question 8

adherence examples

Answer 8

• glycocalyx: Streptocouccs mutans
• Fimbriae: Escherichia coli
• M protein: Streptococcus pyogenes
• Opa protein : Neisseria gonorrhoeae
• Tapered end: Treponema

Question 9

Biofilms (adherence)

Answer 9

• communities of microbes that live together in masses on a surface
  
  • produce extracellular products such as polysaccharides to hold the microbes together
  • biofilms are much more organized than appear
    
    • channels for nutrients and oxygen to penetrate
    • cell to cell communication-quorum sensing
    • 1000x more resistant to biocides than individual cells because of the extracellular materials
    • very important in pathogenicity
    • 65% of infections may involve biofilms; catheters commonly involved

Question 10

Extracellular enzymes (factors that make pathogens invasive: enzymes)

Answer 10

help bacteria invade tissues (exoenzymes)

Question 11

Coagulase (factors that make pathogens invasive: Enzymes)

Answer 11

Coagulate (clot) fibrinogen of blood

-Staphylococcus aureus may produce; helps wall of boils

Question 12

Kinases (factors that make pathogens invasive: enzymes)

Answer 12

digest fibrin clots

-some Staphylococcus and Streptococcus produce

Question 13

Hyaluronidase (factors that make pathogens invasive: enzymes)

Answer 13

• hydrolyses hyaluronic acid which holds certain cells of the body together
  
  • gas gangrene caused by Clostridium

Question 14

Collagenase (Factors that make pathogens invasive: enzymes)

Answer 14

hydrolyzes collagen (forms the connective tissue of muscles)
    -several species of Clostridium which are involved in gas gangrene

Question 15

IgA proteases (factors that make pathogens invasive)

Answer 15

enzymes produced by the bacteria which destroy IgA antibodies that would attack the bacteria

Question 16

Siderophores (factors that make pathogens invasive)

Answer 16

take iron from iron-binding proteins and make available for bacteria

Question 17

Antigenic variation (factors that make pathogens invasive)

Answer 17

pathogen alters surface proteins so that the host antibodies aren’t effective
- influenzavirus; Neisseria gonorrhoeae

Question 18

Capsules (factors that make pathogens invasive)

Answer 18

they help the bacterial cell avoid being engulfed by certain immune cells

- host immune cells engulf invading bacteria (phagocytosis) and destroy them inside the immune cell    - capsule prevents the immune cell from attaching and engulfing bacteria

Question 19

invasions (penetration into the host cell)

Answer 19

• produced by certain microbes when they come in contact with host cell membrane
  
  • E. coli strains and Salmonella strains
  • cause cell membrane to “ruffle” which is due to cytoskeleton being disrupted
  • bacteria can enter cell

Question 20

toxin

Answer 20

substances that contribute to pathogenicity

Question 21

toxigenicity

Answer 21

ability to produce a toxin

Question 22

toxemia

Answer 22

presence of toxin in the host’s blood

Question 23

toxoid

Answer 23

inactivated toxin used in a vaccine

Question 24

antitoxin

Answer 24

antibodies against a specific toxin

Question 25

exotoxin

Answer 25

- source: gram + - relation to microbe: By-products of growing cell - chemistry: protein - fever- no - neutralized by antitoxin- yes - LD50- small (bad that its a small amount) - specific for a structure or function in host cell - genes for toxin may be introduced into bacterial cell by a lysogenic phage; only those strains with lysogenic phage produce the toxin

Question 26

3 types of Exotoxins

Answer 26

1. A-B toxins - most common type - two types: A-enzyme component, B- attachment component ex: diphtheria toxin 2. Membrane-disrupting toxins - lyse hosts cell by: - making protein channels in pm - ex: leukocidins- kill phagocytic white BC & hemolysins- kill RBC - disrupting phospholipid bilayer 3. Superantigens - cause an intense immune response due to release of cytokines from host cells - fever, nausea, vomiting, diarrhea, shock and death - ex: staphylococcal food poisoning exotoxin

Question 27

endotoxins

Answer 27

- source: gram - - relation to microbe- present in LPS of outer membrane - chemistry- lipid - fever- yes - neutralized by antitoxin- no - LD50- relatively large -mechanism by which endotoxin in the gram neg cell causes a fever response in humans. macrophage is a type of WBC

Question 28

endotoxin (figure slide 24)

Answer 28

- fever response (pyrogenic response) - gram neg bacterium ingested by macrophage - bacteria degraded in vacuole inside macrophage and the lipopolysaccharide (LPS) layer of cell wall is released; this causes the macrophage to release interleukin- 1 (IL-1) - IL-1 is carried by blood to hypothalamus of brain (controls body temp) - IL-1 causes hypothalamus to reset the body temp to higher temp --> fever

Question 29

endotoxins cont.

Answer 29

- not destroyed by autoclaving temp - can have dead bacterial cells and still have LPS from cell wall which will cause fever response - drugs, injection materials and medical devices need to be LPS free - LAL test- limulus amoebocyte lysate test- rapid test detect the presence of LAL in pharmaceutical products

Question 30

cytopathic effects of viruses

Answer 30

- vary with the type of virus - may stop cell division - may produce inclusion bodies - may cause cells to fuse together to produce large cell with multiple nuclei - may affect cells so that they no longer stop dividing when they touch each other (contact inhibition) and keep on dividing to form a mass of cells

Question 31

pathogenic properties of fungi

Answer 31

- fungal waste products may cause symptoms - chronic infections provoke an allergic response - tichothecene toxins produced by molds growing in a house or on grain inhibit protein synthesis - ingesting the toxins causes chills, fever, nausea and vomiting - Fusarium; Stachybotrys

Question 32

aflatoxin

Answer 32

toxins produced by some Aspergillus growing under specific conditions; toxic if eaten

Question 33

mycotoxins

Answer 33

neurotoxins; may be quite potent

Question 34

portals of exit

Answer 34

- respiratory tract - coughing and sneezing - gastrointestinal tract - feces and saliva - genitourinary tract - urine and vaginal secretions - skin - blood - biting arthropods and needles or syringes