Colonization, Invasion, and Clinical Disease

Question 1

who benefits (microbe or host) and who is harmed in the following symbiosis?

Answer 1

Question 2

what is the symbiosis of normal microbiota?

Answer 2

mutualists and commensals

Question 3

what does it mean for a member of the normal microbiota to be an opportunistic pathogen?

Answer 3

it can cause disease under the right conditions

Question 4

define pathogenicity

Answer 4

ability of microbe to damage a host

Question 5

define virulence

Answer 5

relative capacity of microbe to cause damage in a host

Question 6

define transmissibility

Answer 6

relative ease with which an infectious agent spreads between hosts

Question 7

define infectivity

Answer 7

capacity of a microbe to become established in a host

Question 8

define virulence factor

Answer 8

traits that enhance pathogenicity

Question 9

what are the major categories of virulence factors in bateria?

Answer 9

adhesins, capsules, toxins

Question 10

what does the attachment specificity in adhesins help bring out?

Answer 10

tissue tropism
host specificity

Question 11

what do capsules do to increase virulence?

Answer 11

mediate adherence and biofilm formation

Question 12

what do toxins do to increase virulence?

Answer 12

damage host cell and tissues

Question 13

what are the two major types of toxins?

Answer 13

exotoxins and endotoxins

Question 14

Difference between exotoxins and endotoxins

Answer 14

exotoxins - secreted by bacterial cell
endotoxins - come from cell wall

Question 15

what is an important endotoxin that produces a systemic inflammatory response in gram negative bacteria?

Answer 15

lipid A portion of LPS

Question 16

what can exotoxins be inactivated with and what is the purpose of this?

Answer 16

inactivated with formaldehyde
resulting toxoid used for vx

Question 17

what are the 3 basic steps in pathogenesis?

Answer 17

colonization, invasion, damage

Question 18

define colonization

Answer 18

establishment of pathogen at appropriate portal of entry

Question 19

Portal of entry examples

Answer 19

mucous membranes, skin, direct deposition beneath skin/mm

Question 20

At what step of pathogenesis are adhesins used?

Answer 20

colonization

Question 21

what are the 3 main portals of entry?

Answer 21

gastrointestinal tract
respiratory tract
urogenital tract

Question 22

what is an example of bacteria co-opting hosts nutrients in colonization?

Answer 22

siderophores - steal iron from iron-binding proteins

Question 23

how are biofilms helpful in colonization?

Answer 23

facilitate quorum sensing - bio film inhabitants can coordinate cellular activities ex. exotoxin production

Question 24

what are invasins?

Answer 24

enzymes that cause local damage to host cells and extracellular matrix

Question 25

what are the two routes of invasion?

Answer 25

paracellular route
transcellular route

Question 26

define paracellular route

Answer 26

passage between epithelial cells

Question 27

define transcellular route

Answer 27

passage through epithelial cells themselves

Question 28

how do pathogens damage the host?

Answer 28

-use host nutrients
-cause direct damage at sites of colonization/invasion
-produce toxins damage sites away from invasion site
-collateral damage from host inflammatory or immune rxns

Question 29

define subclinical infection

Answer 29

infection not leading to disease

Question 30

define acute disease

Answer 30

develops rapidly but lasts a short time

Question 31

define chronic disease

Answer 31

develops slowly is likely to recur for long periods

Question 32

define carriers

Answer 32

no signs/symptoms of disease but are infected and can transmit

Question 33

what are the 4 types of carriers?

Answer 33

passive, incubatory, convalescent, and active

Question 34

what type of carrier would this be - nasal discharge from equine strangles?

Answer 34

active carrier

Question 35

define passive carrier

Answer 35

carry/transmit a pathogen w/o having had the disease

Question 36

define incubatory carrier

Answer 36

transmit a pathogen during the incubation period of the disease when there are no overt signs/symptoms in the carrier

Question 37

define convalescent carrier

Answer 37

harbor/transmit a pathogen while recovering from the disease

Question 38

define active carrier

Answer 38

are completely recovered from the disease but still harbor/transmit the pathogen