Gram negative GI infections

Question 1

Differentiate diarrhea and dysentery

Answer 1

Diarrhea: frequent, loose stools. Painless without fever. Due to increased secretion or decreased reabsorption

Dysentery: pus and blood in stool, painful, with fever, caused by deep microbial invasion or cytotoxins

Question 2

List host defenses present in the GI tract

Answer 2

Mucus secretion
Peristalsis
Acid
Bile 
Digestive enzymes
Secretory IgA, IgG
Phagocytes
GALT
Normal microbiota

Question 3

List some obligate human pathogens that cause GI infection

Answer 3

Salmonelly typhi
Shigella
Helicobacter pylori
Entamoeba histolytica

Question 4

List some zoonotic pathogens that cause GI infection

Answer 4

E coli
Non-typhoid Salmonella
Campylobacter

Question 5

____ has high acid tolerance and a very low infectious inoculum; ____ has moderate acid tolerance; ____ has low acid tolerance and a high infectious dose

Answer 5

Shigella
Salmonella
Vibrio cholerae

Question 6

Staphylococcus aureus and bacillus cereus are two organisms that cause disease by ____ and cause nausea, vomiting, diarrhea

Answer 6

intoxication with pre-formed toxin

Question 7

_ E coli, ______ and _____ virus cause disease through a secretory toxin and cause profuse watery diarrhea with mild pain and fever

Answer 7

ETEC
Vibrio cholerae
Rotavirus

Question 8

EHEC and Shigella cause disease by _____ and produce _____ diarrhea with painful cramps and fever

Answer 8

cytotoxin

bloody

Question 9

EPEC, Salmonella, early Campylobacter, and rotavirus infections can _______ causing ______ diarrhea, cramps, and fever

Answer 9

Invade deeply

purulent bloody

Question 10

Salmonella typhi can cause _____ infection, causing ____ fever

Answer 10

systemic/ disseminated

enteric

Question 11

The #1 overall cause of enteric disease in the US is

Answer 11

Campylobacter

Question 12

List the top four causes of reported enteric disease

Answer 12

1. campylobacter
2. salmonella
3. shigella
4. E coli, mostly EHEC

Question 13

List associations with:

ETEC
EPEC
EHEC
EIEC

Answer 13

ETEC: secretory toxins, heat stable and heat labile, traveler’s diarrhea, syndrome similar to cholera

EPEC: infantile diarrhea, mucosal colonization and destruction, similar to salmonella

EHEC: HUS, cytotoxin mediated, similar to some shigella

EIEC: bacillary dysentery, deep invasion similar to some shigella

Question 14

HUS is caused by ______ toxin, and causes a syndrome of ______, ______, ______, and _______

Answer 14

Cytotoxin/ verotoxin/ shiga toxin

Thrombotic microangiopathy
hemolytic anemia
thrombocytopenia with renal lesions
renal failure

Question 15

_______ produces stools with a rotten egg odor and is resistant to bile salts

Answer 15

Salmonella

Question 16

Reservoirs for Salmonella include

Answer 16

Reptiles

Animals

Question 17

The reservoir for enteric fever caused by Salmonella typhi is the _____, but the organism enters through the ______

Answer 17

gallbladder
Peyer’s patches

infection is specific to humans, carrier state is possible

Question 18

In typhoid fever, ____ cultures become + before ____ cultures

Answer 18

blood before stool

Question 19

______ is an obligate human pathogen transmitted by fecal-oral contamination that produces cytotoxins and is associated with daycare settings

Answer 19

Shigella

Question 20

List common sources of campylobacter transmission

Answer 20

Fecal-oral transmission
contaminated milk and poultry
animals

Question 21

Describe the progression of campylobacter infection

Answer 21

Early gastroenteritis from mucosal colonization and destruction similar to EPEC
Occasional late dysentery from deep invasion, similar to EIEC
Rare enteric fever from systemic dissemination

Question 22

List one unique microscopic feature of campylobacter

Answer 22

darting motility

Question 23

_________ species are spread by fecal-oral transmission or animal contact and cause gastroenteritis with occasional “pseudoappendicitis” (terminal iliitis)

Answer 23

Yersina enterolitica or Yersinia pseudotuberculosis

Yersinia pestis NOT associated with enteric infection

Question 24

List the effects of the vibrio toxin

Answer 24

Secretory toxin that causes constitutive enterocyte cAMP production resulting in massive water and electrolyte secretion- “rice water stools”

Question 25

Vibrio ____ is associated with salt water, shellfish, and sushi and causes gastroenteritis with rare enteric fever. Vibio _____ is associated with salt water, shellfish, and skin abrasions and can cause wound infection or septicemia but NOT gastroenteritis.

Answer 25

Parahemolyticus Vulnificus

Question 26

______ survives in acid environment, but produces ureases that hydrolyze urea to raise gastric pH

Answer 26

Helicobacter pylori

Question 27

List steps in diagnosis of enteric infections

Answer 27

Gross stool examination Microscopic stool examination for PMNs, occult blood, ova, darting motility Stool culture- selective media ELISA tests for specific antigens

Question 28

Therapy for enteric infection is often ______ only and may include medications that cause symptomatic relief such as bismuth subsalicylate, loperamide, dihenoxylate

Answer 28

Supportive

Question 29

Do not use medications that reduce _______ if there is blood or pus in the stool

Answer 29

GI motility

Question 30

Antibiotics are only used in enteric infection if:

Answer 30

High risk patient Protracted/ severe infection - use fluoroquinolones such as ciprofloxacin - never use antibiotics in EHEC

Question 31

Contrast measures to prevent vs treat helicobacter pylori infection

Answer 31

Prevention: minimize agents that raise gastric pH- PPIs, H2 antagonists, antacids Treatment: 2+ antibiotics + PPI (to diminish inflammation, damage, symptoms)