GI disease

Question 1

What are the two options for GI bacterial disease

Answer 1

either toxin-mediated or organism-mediated

Question 2

describe the presentation and cause of toxin-mediated foodborne disease

Answer 2

acute onset of nausea and vomiting less than 6 hours after eating contaminated food. the pre-formed toxin is usually already in the food from bacterial food growth

NO fever. Diarrhea is rare.

Question 3

What are two common organisms to suspect of toxin-mediated foodborne disease

Answer 3

Staph aureus and bacillus cereus

Question 4

What often causes heartburn

Answer 4

H. pylori

Question 5

how is h. pylori spread

Answer 5

fecal oral

Question 6

How does it create it’s survivable niche

Answer 6

it secretes urease to increase the pH of its environment and allow it to survive

Question 7

What is a virulence factor for the H. pylori

Answer 7

CagA. It is injected into cells causing inflammation

Question 8

Decribe the course of H. Pylori and the sequelae

Answer 8

h. pylori will cause chronic superficial gastritis (weeks to months). Over the years it can lead to several things: peptic ulcer disease, chronic superficial gastritis, gastric lymphoma, gastric adenocarcinoma (from chronis atrophic gastritis)

Question 9

What are the pathogens that cause dysentery, leukocytosis, and PMN’s in stool

Answer 9

C. difficile, STEC, salmonella, shigella, C. jejuni, Y. enterocolitica

Question 10

What are the pathogens that cause diarrhea and fever

Answer 10

C. difficile, salmonella, shigella, C. jejuni, and yersinia enterocolitica. viral diarrhea (sometimes). STEC (sometimes

Question 11

What never causes fevery diarrhea

Answer 11

ETEC

Question 12

Describe the pathogenesis of C. difficile

Answer 12

fecal-oral spread. The C. dificile will overgrow and realease Toxins A and B. These will inactivate Rho which is an important cytoskeleton protein. this disruption of the cytoskeleton leads to cell apoptosis and inflammation leading to colitis

Question 13

describe the pathogenesis of STEC

Answer 13

beef will get infected with it. This will adhere to the colon. leading to Stx 1/2 (shiga-like toxin) which will depurinate rRNA and inhibit protein synthesis. This leads to local GI inflammation and hemorrhage. Once it breaks through to a systemic ilness, there will be endothelial damage and deposition of immune complex in the kidney leading to hemolytic uremic syndrome.

Question 14

Describe the mechanism of EHEC adhesion

Answer 14

It is a type III secretion system that will inject receptor AND effector proteins. This will rearrange the cytoskeleton to create a pedestal. This is a super-tight adherence. Remember, this does NOT leads to exotoxin injection

Question 15

Describe the laboratory testing for EHEC

Answer 15

look at it on the sorbitol-mackonkey agar which will detect E. coli O157:H7 which does NOT ferment soritol. You can also do an immunoassay for Stx-1 and stx-2 which will detect all serotypes of EHEC

Question 16

How do the virulence factors of STX-1/2 get transferred

Answer 16

by bacteriophages.

Question 17

What will an antibiotic do to STEC

Answer 17

It will damage the bacteria leading to release of lytic virus and increased toxin production. ALSO, this will be able to transfer to other E. coli strains. There is a significant serotype diversity among the EHEC

Question 18

how does Salmonella infect and invade

Answer 18

It will be passed zoonotically from a bird (only non-typhi salmonella) or from fecal-oral human hosts (S. typhi and paratyphi). It will infect M-cells in the GI mucosa leading to inflammation and diarrhea. If it gets into the blood via the lymphatics, it will cause disseminated disease leading to enteric fever (this really is only S. typhi and S. paratyphi).

Question 19

What is the mechanism of Salmonella invasion

Answer 19

It is similar to STEC in that it uses a secretion system that will inject effector proteins. It will lead to cytoskeletal rearrangement and membrane ruffling. Unlike the STEC, though, it will be ENGULFED by the cell leading to uptake

Question 20

What does the lactose + pH indicator on a MacConkey say

Answer 20

basically, the E. coli are all lactose fermentors, but salmonella and shigella are not. Therefore, if you have a non-lactose fermenting thing in a person with diarrhea, you know it is one of these

Question 21

What is the most common cause of traveler’s diarrhea

Answer 21

ETEC is the most common cause of traveler’s diarrhea. It is usually mid and self-limited. It is spread by fecal-oral.

also, don’t forget V. cholerae. This has a variety of presentation from mild to severe, life-threatening illness. spread fecally oroally. Also can be contracted from coastal water shellfish

Question 22

For ETEC and cholera what is the mechanism

Answer 22

Basically, there is growth of the ETEC or cholera in the GI. The toxin created is an A-B toxin which will get into the GI cells and activate cAMP. This leads to increased ion and H2O efflux OUT of the cell into the lumen leading to secretory diarrhea and dehydration