Invasive gram negative pathogens of GI tract

Question 1

what are the 3 mechanisms bacteria can use to cause infections

Answer 1

1 - invade the mucous membrane
2 - toxin producers
3 - hybrid of the two above

Question 2

what are the 2 main gram (-) bacterial species that cause infections by invasion of the mucous membrane

Answer 2

salmonella and shigella

Question 3

shigella species of gram negative pathogens has 4 subgroups distinguished by what antigen

Answer 3

O antigen (based on structure of LPS

Question 4

what is RpoS ?

Answer 4

transcription factor that causes acid resistance in shigella allowing pathogen to pass through stomach

Question 5

which gram negative bacteria has a small inoculum size ? large ?

Answer 5

shigella is small, salmonella is large

Question 6

explain how shigella pathogens invade humans

Answer 6

1 - enter host M cells for transport to basal surface
2-released at lamina propria and ate by macrophages causing inflammatory response
3- pathogens not eaten ingested by epithelial cells and put in vesicle
4-shigella proteins lyse the vesicle
5- spread locally intracellulary via IcsA

Question 7

which is resistant to pathogen infection in humans, the mucous surface or basal surface

Answer 7

basal surface

Question 8

what do shigella pathogens produce to signal human M cells to pick them up for transport to basal surface

Answer 8

shigella pathogens have proteins called “invasion plasmid antigens”

Question 9

what is IcsA

Answer 9

protein ATPase of shigella causing polymerization of actin which pushes shigella cells into adjacent epithelial cells w/o going into cytoplasm and getting destroyed by immune system

Question 10

is shigella a localized infection or systemic ? why ?

Answer 10

localized because just stays in epithelial cells and away from blood stream

Question 11

what develops when the invaded epithelial cells die off from shigella infection

Answer 11

ulcer

Question 12

what specific subgroup of shigella induces a watery diarhea stool

Answer 12

shigella sonnei (most common)

Question 13

what specific type of shigella produces the Shiga toxin and is the most severe of shigella diseases

Answer 13

Shigella dysenteria type 1

Question 14

what does the Shiga toxin in shigela dysenteria cause

Answer 14

• kills intestinal epithelial and endothelial cells=more diarhea
• dirsupts Na absortion

Question 15

Salmonella pathogen can cause what 2 diseases

Answer 15

1- Gastroenteritis

2-Typhoid fever

Question 16

how is salmonella transmitted to humans

Answer 16

fecal (human or animal) to mouth

Question 17

Is salmonella acid resistant or not ?

Answer 17

Not as acid resistant as shigella

Question 18

if salmonella pathogens survive through the low acidity of the stomach, the low pH will induce what ?

Answer 18

pathogenicity islands on large virulence proteins

aka - virulence proteins

Question 19

how does salmonella pathogen invade the human

Answer 19

1-approach cell mucosal surface and increase Ca levels
2-induces surface “ruffles” and uptake of pathogens into vesicles
3-remain in vesicles for hours
4 - released into lamina propria and induces Na and Cl loss causing diarhrea
5 - Macrophages eat or if escape become transient

Question 20

how is salmonella typhi, which causes typhoid fever, different from normal salmonella species

Answer 20

it is not killed by macrophages, these survive and grow/replicate inside macrophages then enter lymphatic system becoming system (much more severe)

Question 21

T/F Salmonella typhi has an animal resovoir

Answer 21

F, it is strictly a human pathogen

Question 22

Who is typhoid mary and explain her situation

Answer 22

she was a carrier of salmonella typhi w/o knowing

Question 23

where in the body do salmonella typhi carriers have colonized pathogens

Answer 23

gall bladders

Question 24

how do you diagnose what species of invasive pathogens are causing a disease

Answer 24

stool cultures

Question 25

how do you treat enteric/GI diseases

Answer 25

antibiotics

Question 26

which pathogen invades the mucous membrane by altering the hosts ion signalling pathways ?

Answer 26

salmonella