GI Tract Infections Flashcards
1
Q
What is considered true food poisoning?
A
- the consumption of preformed toxin within the food that may be chemical or bacterial in nature - the toxins survive cooking and heating
2
Q
What is a toxin associated infection?
A
- the food is simply the vehicle for the pathogen to grow and multiply to numbers large enough to cause infection
- ex. Campylobacter and Salmonella
3
Q
What are the three ways for GI infections to cause disease?
A
- Fluid imbalance (changes balance of water and electrolytes in the small bowel, leading to a massive fluid secretion)
- Cell destruction and inflammation (invasion/cytotoxin production)
- Invasion (penetrate the intestinal mucosa -> spread and multiply outside the bowel)
4
Q
Diarrhea is an increase in fluid and electrolyte loss in the ____
A
gut lumen
5
Q
How many different groups of E.coli are there?
A
6
6
Q
Describe enteropathogenic E.coli (EPEC)
A
- affects babies and young children
- virulence factors: adhesins, bundle forming pili and intimin - attaches to epithelial cells and microvillus
7
Q
Describe enterotoxigenic E.coli (ETEC)
A
- affects children
- binds to receptors on cell membrane of small intestine
- plasmid encoded toxins
- heat labile toxin (LT) - similar mode of action as cholera toxin
- heat stable toxin (ST) - increase in guanylate cyclase activity -> increase cGMP -> increases fluid secretion
8
Q
Describe enterohaemorrhagic E. coli (EHEC)
A
- invasive AND makes toxins
- verotoxins 1 and 2 (VTEC)
- aka “shiga like toxin”
- SLT-1 and SLT-2
- toxins damage the large intestine (inhibit protein synthesis)
- ulceration and bleeding
- serotype O157:H7
9
Q
What syndromes/ symptoms can be caused by enterohaemorrhagic E.col?i
A
- hemorrhagic colitis (HC)- destruction of mucosa leads to hemorrhage
- hemolytic uremic syndrome (HUS) - toxin gets absorbed in bloodstream. Verotoxin receptors found in renal epithelium- may account for kidney damage
- causes symptoms of anemia due to destruction of RBCs and low platelet count and sudden kidney damage
10
Q
Describe enteroinvasive E.coli (EIEC)?
A
- attach to the mucosa of the large intestine
- invade cells by endocytosis, multiply, spread to adjacent cells, cause tissue destruction and then inflammation and ulceration
11
Q
Describe enteroaggregative E.coli? (EAEC)
A
- stacked brick appearance on tissue culture cells
- aggregation: plasmid encoded fimbria
- toxins produced by role in diarrheal disease is uncertain
12
Q
Describe diffuse aggregative E.coli (DAEC)
A
alpha hemolysin and cytotoxic necrotizing factor 1
13
Q
What test could be done to identify the EHEC strain of E.coli?
A
testing for shiga toxins
14
Q
What can be done to identify the EIEC strain of E.coli?
A
invasion of tissue culture cells or the presence of invasion associated genes
15
Q
Do you have to use antibiotic therapy to treat diarrhea caused by E.coli?
A
- no
- need to focus on fluid replacement
16
Q
What is the consequence of using antidiarrheal medications?
A
- increase the contact time of the pathogen with the intestinal wall - therefore this increases the disease severity
17
Q
What is HUS and what is needed to treat it?
A
- known as hemolytic uremic syndrome
- is a complication of an E.coli infection and can cause kidney failure
- need to undergo dialysis
18
Q
What is the best method of prevention of an E.coli infection?
A
- clean water, pasteurization, proper cooking
- boil it, peel it, cook it or forget it
19
Q
Whittier the most common symptoms of salmonella poisoning?
A
- meat, poultry, eggs, dairy products and farmed fish
20
Q
When are the symptoms of salmonella noticeable after ingestion?
A
- 6-48 hours after ingestion
21
Q
What aret eh most common symptoms of salmonella poisoning?
A
- nausea, vomiting and diarrhea
22
Q
Salmonella may be excreted in ___ for several weeks post infection
A
feces
23
Q
Food handlers that test positive for salmonella are excluded from work until ______
A
3 fecal specimens come back negative
24
Q
What bacteria is known to cause typhoid fever?
A
- S. typhi
25
What is the general spread of typhoid fever?
- fecal contamination of food or water
26
What are the symptoms of typhoid fever?
- headache
- fever
- malaise
- abdominal tenderness
- constipation
27
Describe enteric fever
(aka typhoid fever)
- once you contract it, you are a chronic colonizer- it stays in the gallbladder and the biliary tree, causing persistent shedding that can last for years
28
Campylobacter species are the most common cause of bacterial _____
gastroenteritis
29
Campylobacter is a heat ___ bacteria
sensitive
30
What are the most common symptoms of campylobacter infections?
- diarrhea with blood and pus (2-3 days)
- abdominal pain that is longer lasting
- self-limiting disease
31
How long after campylobacter infestation do symptoms typically arise?
- within 2-5 days
32
What are the sources of a campylobacter infection?
poultry
| contaminated meat, water unpasteurized mill
33
What are the main antibiotic therapies for a campylobacter infection?
- fluoroquinolones
| - macrolides
34
What pathogen causes cholera?
- Vibrio cholera
35
Where does cholera have the most effect in the world?
- SE Asia, parts of SA and Africa
36
What spreads cholera infections?
- cholera is spread by contaminated food and water - never spread by human contact
37
What are the symptoms associated with a cholera infection?
- severe watery, non bloody diarrhea that is known as rice water diarrhea due to its appearance
- this is due to the presence of a enterotoxin in the GI tract
- can be a loss of fluid up to 1 L an hour, which can cause dehydration, metabolic acidosis, hypokalaemia and hypovolaemic shock resulting in cardiac failure
38
What is the pathogenesis of vibrio cholera?
- vibrio cholerae is ingested in large numbers
- sensitive to stomach acid, large doses needed to cause disease unless the patient is achlorhydria or taking antacids
- colonization of the small intestine depends on the motility, production of mucinase or the attachment to specific receptors- this can
all lead to toxin production
- this in the end leads to a massive loss of fluid and electrolytes form the GI tract
39
Shigella species have a ___ ID50 (or the amount of bacteria that produces an infection in 50% of individuals)
low
40
Shigella species are ____ transmitted and have no____
easily
| animal reservoir
41
What is the pathogenesis of a shigella infection?
- shigella attach to and invade the mucosal epithelium of the distal ileum and the colon, causing inflammation and ulceration
- they produce a toxin that also can cause damage to the epithelial and kidney cells
42
What is the treatment options for shigellosis?
- rehydration
| - antibiotics in severe cases
43
C. diff infections cause what?
diarrhea (can be mild-watery) to life threatening toxic megacolon needing surgical intervention
44
What is the characteristic sign of c. diff infections?
- changing the pseudomembrane to pseudomembranous colitis
| - caused by an influx of neutrophils, fibrin, mucin and cellular debris
45
What is the treatment for C. diff infections?
- antibiotics
| - fecal transplants
46
What is food poisoning caused by?
- Staph aureus enterotoxin and Clotridium botulinum toxin (consumption of preformed toxins in food)
- S. aureus enterotoxin
47
Describe the S aureus enterotoxin
- heat stable and resistance to stomach/small intestine enzymes
- mechanism of action: super antigen, binds to MHC class 2 molecules -> T cell stimulation
- effects on CNS - severe vomiting within 3-6 hours after consumption
- no diarrhea
48
What pathogen causes listeriosis?
- liesteria monocytogenes
49
Listeria is a ___ borne illness that can multiply at 4 degrees, with an infectious dose of under 1000
food
50
Who is at an enhanced risk of listeriosis?
- pregnant women
| - immunocompromised individuals
51
Rotavirus is spread via ____ transmission
oral-fecal
52
What are the symptoms of a rotavirus infection?
- vomiting
- diarrhea
- fever
53
What is the treatment for a rotavirus infection?
- fluid and salt replacement
54
What virus family is norovirus from?
- calcivirus family
55
What does norovirus cause?
- gastroenteritis
56
What is the incubation of period of norovirus?
- 24-48 hours
57
What is the rate of infection of those coming into contact with norovirus?
- 50%
58
How is norovirus detected? Is it culturable?
- NO -not culturable
| - detected by electron microscopy or PCR
