Invasive gram-neg bacterial pathogens of GI tract

Question 1

Enterobacteriaceae and Vibronoaceae are both prolific colonizers of what?

Answer 1

mucosal surfaces

Question 2

what is a mucosal surface?

Answer 2

Surface that interacts with air that has associated glands for secreting mucus.

Question 3

what are the defenses of the mucosal surface?

Answer 3

• Innate immunity
• Adaptive immunity
• Nonspecific barrier defenses

Question 4

transmission of gram-negative mucosal pathogens: via what pathways?

Answer 4

the “seven F’s”

feces to mouth

Question 5

what are the “7 F’s”?

Answer 5

Feces
Food
Fluids
Fingers
Flies
Fomites
Fornication

Question 6

what is the lowest range of inoculum size? (Shigella dysenteriae)

Answer 6

50-100 organisms

Question 7

what are the natural barrier defenses for gram-negative pathogens?

Answer 7

A) secretory substances
B) anatomical and physiological
barriers
C) indigenous microbiota

Question 8

what is the pH level of the gastrointestinal tract?

Answer 8

1-2 all the way up to 9

Question 9

how does a Lysozyme (a.k.a muramidase) destroy a bacteria?

Answer 9

cleaves beta 1,4 glycosidic linkages between NAM and NAG

-only works on exposed murien (gram positive)

Question 10

what is lactoferrin’s main function?

Answer 10

sequester iron

Question 11

how does Cathelicidin work toward destroying a microbe?

Answer 11

Disrupts bacterial membranes of BOTH gram - and gram + bacteria

Question 12

What do Defensins create on the target microbe?

Answer 12

pores

Question 13

what are the 2 types of Defensins? where are they produced?

Answer 13

Alpha - produced by neutrophils and paneth cells (intestines)

Beta- produced by epithelial cells

Question 14

How do pathogenic bacteria overcome these innate barrier defenses?

Answer 14

1) Acid resistance
2) Fimbriae/Pili
3) Bacterial structures

Question 15

________ are an Important Component of Mucosal Immunity

Answer 15

Macrophages

Question 16

Activation of pattern recognition receptors on macrophages also initiates the _______ _________

Answer 16

Inflammatory response

Question 17

Which TLR will be most important for identifying gram-negative bacteria?

Answer 17

TLR4

Question 18

Inflammatory cytokines, such as TNF-α can disrupt the _________ ______ between epithelial cells

Answer 18

Tight junctions

Question 19

the Four species of Shigella are distinguished by what?

Answer 19

The O antigen

Question 20

T/F: the Inoculum size of Shigella is very small

Answer 20

True

Question 21

_____ _______ facilitates survival of Shigella through the stomach

Answer 21

Acid resistance

Question 22

where will Shigella multiply and colonize?

Answer 22

in the Colon

Question 23

Shigella microbes will travel through the mucosal surfaces, eventually entering what type of cell?

Answer 23

M cells

Question 24

how does Shigella enter the M cells?

Answer 24

using the outer membrane protein “invasion plasmid antigens”

Question 25

once it has entered the M cells, where is it released?

Answer 25

into the lamina propria- causes inflammatory response

Question 26

what response to Shigella actually causes illness?

Answer 26

inflammatory response as a result of macrophage activity

Question 27

Intracellular spread of Shigella facilitated by _______, an ATPase that causes ________

Answer 27

IcsA actin polymerization

Question 28

what develops when invaded Shigella cells die and slough off?

Answer 28

Ulcer

Question 29

what immune cell can be found in the stool of people infected with Shigella?

Answer 29

Neutrophils

Question 30

All species of Shigella will induce an _______ ______ with leukocytes in the stool

Answer 30

inflammatory diarrhea

Question 31

which Shigella species induces a watery stool?

Answer 31

S. sonnei

Question 32

why is S. dysenteriae (Shigella) different from other forms of the genus?

Answer 32

it produces SHIGA TOXIN

Question 33

what does Shiga toxin do?

Answer 33

kills intestinal epithelium and endothelial cells disrupts Na absorption

Question 34

Salmonella causes what 2 main diseases?

Answer 34

A) Gastroenteritis | B) Typhoid fever

Question 35

which species of Salmonella causes typhoid fever?

Answer 35

Salmonella typhi

Question 36

how is Salmonella transmitted?

Answer 36

fecal-oral transmission can be between human or animal

Question 37

T/F: a relatively small inoculum is required for Salmonella

Answer 37

False- large inoculum required

Question 38

Salmonella is more _____-sensitive than shigellae

Answer 38

acid

Question 39

in Salmonella- a low pH induces the expression of at least 40 proteins found on what?

Answer 39

pathogenicity islands on large virulence plasmids

Question 40

when Salmonella approaches a host cell surface, it causes the increase of what within the cell?

Answer 40

Calcium | Ca2+

Question 41

the forced uptake of Salmonella into the host cell is known as what?

Answer 41

Microbe-directed phagocytosis

Question 42

unlike Shigella, Salmonella remains within ________ for many hours after entering

Answer 42

cell vesicles

Question 43

when salmonella is released to the lamina propria, what does it induce?

Answer 43

a loss of Na and Cl from the host cell

Question 44

Salmonella typhi will survive and grow within the _______

Answer 44

macrophages

Question 45

Salmonella typhi will travel from the gastrointestinal tract into the ____ ______

Answer 45

lymphatic system

Question 46

Salmonella typhi cannot survive in a _______ reservoir, meaning its strictly a what?

Answer 46

- cannot survive in an animal reservoir | - strictly a human pathogen

Question 47

carriers of Salmonella typhi can often be _____

Answer 47

asymptomatic -they have colonized gall bladders

Question 48

what is a unique property of the Salmonella strains that cause typhoid fever?

Answer 48

they multiply in macrophages in the: A) liver B) spleen C) bone marrow

Question 49

Shigella and Salmonella are both invasive, so both are able to do what?

Answer 49

invade into the intestinal epithelial cells | both can invade host cells

Question 50

differences between Shigella and Salmonella:

Answer 50

1) Inoculum size (i.e., acid sensitivity) 2) Bacteremia (only Salmonella) 3) Species that cause severe disease are very dissimilar.

Question 51

Salmonella and Shigella species both cause what symptoms upon infection?

Answer 51

``` Large Intestine Small Volume of Stool Bloody Stool Leukocytes in Stool Tissue Ulcerations ```