Unit 2- Determinants of Pathogenicity

Question 1

What is a niche

Answer 1

a compartment with unique properties (ie. temperature, pH, nutrients)

Question 2

What proportion of body cells do microbes make up?

Answer 2

90%

Question 3

When do microbes start colonizing the human body

Answer 3

at birth and throughout lifetime

Question 4

What is commensalism?

Answer 4

One organism benefiting without harming the other

Question 5

What is mutualism?

Answer 5

Two organisms cooperating to both benefit (ie. bacteria in the grass cows eat help the cow digest grass)

Question 6

What is parasitism?

Answer 6

One organism benefiting at the expense of another (harm is done to one)

Question 7

How long does colonization of a baby take after birth?

Answer 7

8-12 hours

Question 8

What protects the womb from vaginal microbes?

Answer 8

Fetal membranes

Question 9

What microbes are exposed to bottle-fed babies?

Answer 9

coliforms, lactobacilli, enteric strepotococci, staphylococci

Question 10

What microbes are exposed to breast-fed babies?

Answer 10

bifidobacterium

Question 11

Where in the body do normal flora microbes colonize?

Answer 11

Skin, mucous membranes, upper respiratory tract, gastrointestinal tract, outer opening of urethra, external genitalia, vagina, external ear and canal, external eye (lids, lash follicles)

Question 12

What are microbes that are temporary in the body called

Answer 12

Transients

Question 13

What are long term/permanent microbes called?

Answer 13

Residents

Question 14

Pathogen?

Answer 14

Parasitic microbes with the potential to cause disease

Question 15

What a true/primary pathogens?

Answer 15

Those likely to cause disease in people with normal immune system

Question 16

What are opportunistic pathogens?

Answer 16

They cause disease in immunocompromised people

Question 17

What factors weaken host defenses and increase susceptibility to infection?

Answer 17

Old age, extreme youth, genetic defects or acquired defects in immunity, surgery and organ transplants, organic disease (liver, cancer, diabetes), chemotherapy/immunosuppressive drugs, physical and mental stress and other infections

Question 18

Invasion?

Answer 18

Microbes enter into germ-free tissues or cells

Question 19

Infection

Answer 19

Microbe spreads throughout the tissues and body

Question 20

Virulence

Answer 20

degree of harm caused by pathogen

Question 21

virulence factors

Answer 21

Intrinsic characteristics of pathogens that contribute to virulence

Question 22

infectious dose (ID)

Answer 22

minimum number of microbes required to cause illness

Question 23

lethal dose (LD)

Answer 23

minimum number of microbes needed to cause death

Question 24

Virulence factors of E. coli?

Answer 24

1) toxins to break down gut lining 2) rapid growth 3) ability to enter gut lining (ingesting as little as 10 cells may cause illness)

Question 25

Virulence factors of Vibrio cholera

Answer 25

1) produces cholera toxin (which draws salts and water into intestine, causing diarrhea) (ingesting 10^6-10^11 cells are needed to cause illness)

Question 26

ID50?

Answer 26

minimum amount of microbes required to infect 50% of a given population

Question 27

LD50

Answer 27

amoutn of microbes needed to kill 50% of a given population

Question 28

the ____the ID50 and LD50, the more virulent the pathogen

Answer 28

lower

Question 29

Adhesion?

Answer 29

adsorption to host cells and tissues

Question 30

Adhesion mechanisms of bacteria

Answer 30

Fimbrae (non-specific), capsule

Question 31

Adhesion mechanisms of viruses

Answer 31

Glycoproteins (specific), Hemagglutinin (non-specific)

Question 32

Evasion?

Answer 32

Antiphagocytic factor, prevent being eaten from immune cell

Question 33

3 strategies to avoid phagocytosis?

Answer 33

1) Capsule- slimy layer preventing phagocytosis
2) Toxins- defense against phagocytic cells
3) Leukocidins- toxins that directly kill WBCs

Question 34

Intracellular Microbes do what?

Answer 34

hide inside host cells, and ecrete molecules into a target cell to make it easier to enter

Question 35

Evasive factors of H. pylori?

Answer 35

1) urease produces NH4 to neutralize stomach acid

2) flagella