GI Infections Flashcards
1
Q
What is unique about Food Poisoning?
A
- preformed toxins
- very short incubation (because they don’t need to multiply - its the exotoxin that is doing the damage)
- examples: S. aureus, bacillus cereus
2
Q
What do GRAM (+) cocci look like?
rods/spiral/sphere
A
GRAM (+) cocci:
grape-like clusters
3
Q
meaning of
catalase +/-
A
catalase + (which means it breaks down peroxide into water and O2 (contributes to bubbling rxn)
4
Q
Explain Mannitol Salt agar?
A
grows on manitol salt agar (MSA) and turns plate yellow
-only gram (+) can grow
-S. aureus metabolizes mannitol (yellow plate)
(S. Epi plate doesn’t turn yellow, stays pink)
5
Q
S. aureus characteristics
A
gram (+) catalase (+) grape like clusters SALT tolerant normally found in approx. 30% of humans (nose) mannitol SALT agar (yellow)
6
Q
S. aureus virulence
endotoxin / exotoxin
A
- enterotoxin!
- heat stable
- don’t let food sit at room temp and it will not have a chance to grow
7
Q
S. aureus signs and symptoms
A
Symptoms: 3-6 hours after ingestion Severe vomiting Cramps With/w.out diarrhea Recovery 24-48 hours
8
Q
S. aureus transmission
A
ingestion of contaminated food
-potato salad left out at room temp
9
Q
Bacillus cereus characteristics
A
gram (+) rod produces endospores (you remember the other species anthrax)
10
Q
Bacillus cereus virulence
A
2 forms of enterotoxins cause gastroenteritis:
- Emetic: *think RICE (buzz word)
- incubation is less than 6 hours
- duration is 8-10 hours
- heat stable - Diarrhea: think MEAT and VEGETABLES
- incubation is great than 6 hours
- duration is 20-36 hours
- heat liable
- profuse watery diarrhea (via increased cAMP)
11
Q
Bacillus cereus transmission
A
ingestion
12
Q
food poisoning
A
S. aureus, bacillus cereus
13
Q
examples of enterobacteria?
A
E. Coli
Salmonella
Shigella
14
Q
enterobaceria common characteristics
A
Gram negative rods Facultative anaerobes Ferment glucose MacConkey agar Catalase positive Oxidase negative
15
Q
where are enterobacteria found?
A
-for E. Coli and Shigella fecal contamination of:
soil
water
vegetation
-for Salmonella:
intestinal tract of humans and animals
note: enterobacteria cause GI infections (IT’S the organism causing us problems - they survive the stomach and make it to the intestine)
(not the same as food poisoning - where its the preformed toxin causing us problems)
16
Q
MacConkey agar
A
Light pink color
Selective: only Gram negatives
Differential: detects lactose fermentation
Lactose positive: pink/purple colonies
Lactose negative: colorless/beige colonies
17
Q
EMB agar
A
Lactose fermenter: dark colonies
E. coli: metallic green sheen
18
Q
What is the #1 cause of UTI infections in normal healthy people?
(hint:
we use this bacteria to test the fecal contamination of the water supply
-most strains of this bacteria are non-pathogenic)
A
E. Coli
19
Q
Enterotoxigenic (ETEC)
A
- travelers diarrhea (fairly common)
- strain of ecoli
20
Q
ETEC virulence
A
2 toxins:
- LT1 is heat liable and increases cAMP
- STa is heat stable and increases cGMP
21
Q
ETEC transmission
A
*consuming fecal contaminated water or food
returning from a few days in Mexico and suddenly it hits you: (even brushing teeth, salad wash – their water sanitation system just is not what ours is here – most people from the area probably are adapted to it
22
Q
ETEC signs and symptoms
A
Watery diarrhea
Abdominal cramps
Fever
Nausea/vomiting (possible, but not always)
Onset: 24 to 72 hours
Duration: 3 to 5 days
23
Q
Enteroinvasive (EIEC)
A
rare in US
24
Q
EIEC virulence
A
- no enterotoxin produced
* has to invade the GI epithelium to cause illness
25
EIEC symptoms
```
Onset: 10 to 18 hours
Watery diarrhea
Fever
Abdominal cramps
Bloody diarrhea w/leukocytes
Duration: 3 to 5 days
```
*once bacteria has invaded the immune system is activated and the watery diarrhea turns into Bloody diarrhea w/leukocytes
26
Enterohemorrhagic (EHEC) characteristics
- very infective, only requires 10 - 100 organisms
| - Buzz word: undercooked hamburgers
27
EHEC transmission
```
Normally found in GI tract of
Cattle
Goats
Sheep
-spread fecal to oral
```
```
examples:
Alfalfa sprouts
Unpasteurized milk, juice
Petting zoos
Lettuce, spinach
```
28
EHEC virulence
Produces powerful shiga-like toxins
(The toxin this e. coli produces is actually picked up from shigella; moved via phage – transduction)
Stx1 and Stx2 (verotoxin)
disrupts protein synthesis
receptor found on intestinal cells and kidney cells
29
EHEC symptoms
```
Incubation: 3 to 4 days
Start with watery diarrhea
Progresses to gross bloody diarrhea
Severe stomach cramps
Low grade fever
Vomiting (not common)
Duration: 3 to 7 days
```
30
EHEC complications
This shit can cause LIFE LONG complications!
Two syndromes:
1. Hemorrhagic Colitis (Bloody diarrhea) - attacking intestinal cells
2. Hemolytic Uremic Syndrome (HUS) - infection gets into blood and travels to kidney and start killing kidney cells
31
Discuss Hemolytic Uremic Syndrome (HUS)
| Around 5–10% of O157:H7 cases - children/elderly
(EHEC complication)
Thrombocytopenia
-decrease in platelets – so cant clot and you bleed more
Hemolytic anemia
Renal failure
Death: 3-5% patients
32
How much antibiotic should you give to a patient with HUS?
| EHEC complication
*Antibiotics will actually stress the e. coli cells in this case and the e coli responds by pumping out more toxin (so don’t give an antibiotic!!)
Won't need to know treatment specifically but))
instead:
Dialysis for kidneys
fluids to combat dehydration
*A kid could be on dialysis for the rest of his life (because he ate a hamburger)
33
EHEC diagnosis (lab characteristics)
-collect fecal specimens
Plate on Sorbitol-MacConkey agar
select colorless colonies
95% E. coli are lactose +, sorbitol +, BUT O157:H7 is lactose +, sorbitol –
OR
Direct detection of the shiga-like toxin (verotoxin)
Direct PCR to detect presence of SLT genes
```
WHat won't work:
urine specimen (infection is not in kidneys)
```
34
Sorbitol-MacConkey agar?
95% E. coli are lactose +, sorbitol +
O157:H7 lactose +, sorbitol –
In sorbitol MacConkey agar, lactose is replaced by sorbitol.
O157:H7 is unable to ferment sorbitol (colorless colonies)
35
Other infections caused by E. Coli
UTI (urinary tract infection):
```
Endogenous infection (coming from your bladder)
Colon to urethra, then ascends into bladder
*pili is most important virulence factor in UTI infection (if it didn’t have this the flow of urine would wash it away)
```
(E coli is one of the major causes of)
Neonatal meningitis:
Mother to child (vertical transmission)
Septicemia: starts in GI tract or urinary tract then spreads
36
Salmonella characteritics
gram (–) rod
LPS
colorless on MacConkey agar (does not ferment lactose)
*H2S positive
Only two species of Salmonella
BUT over 2300 different strains
reptiles carry both species (S. enterica and S. bongori)
S. enterica enteritidis - causes enteric infections with diarrhea (this is the one she cares about for this lecture)
37
salmonella transmission
*ingesting contaminated food or water
38
salmonella virulence
Bacteria multiply and **invade the intestinal mucosa
Ability to attach (colonization)
Ability to enter (invasion) columnar epithelial cells and M cells
Divides in the phagocytic vesicles and does not escape to the cytoplasm of the host cell
39
salmonella symptoms
Short incubation time: 12-72 hours
- Diarrhea with mucus +/- blood (mucus, puss, leukocytes, it’s all the same, it’s from the immune response)
- Fever
- Abdominal cramping
duration: 2 to 7 days
40
shrigella transmission
super infective (infective dose: 10 cells)
again fecal - oral route
Day care , nursing home – coming in contact with fecal matter
41
shrigella characteristics
Lactose non-fermenter
**H2S negative (differentiate from salmonella!)
No animal reservoir, only humans
```
4 species that are human pathogens
Shigella sonnei
most common in U.S.
Shigella dysenteriae
most severe disease
```
Shigella flexneri
Shigella boydii
42
shrigella virulence
similar to salomella - *invades intestinal epithelium (mcell) then replicates in macrophage, and spreads from cell cytoplasm to cell cytoplasm
Shiga toxin
- inhibits protein synthesis
- another one that - Damages intestinal epithelial cells and kidney cells (Hemolytic Uremic Syndrome)
43
shrigella symptoms
```
Incubation 1-4 days
Watery diarrhea
Abdominal cramps
Fever
Bloody diarrhea with mucus
*Dysentery: frequent passage of stools containing blood and mucous (small amounts of diarrhea occurring many times throughout the day)
duration: 2 to 3 days
```
44
lab diagnostics / characteristics of:
Vibrio cholera and Vibrio parahaemolyticus
```
Gram negative, curved rod
Facultative anaerobes
Marine organisms
Halophiles** (organisms that live in high salt con.)
Oxidase positive
```
45
Vibrio cholera transmission
ingestion of contaminated food or water.
46
Vibrio cholera symptoms
incubation: 2 to 3 days
Presence of toxin causes cAMP concentration to rise, which results in massive loss of water and electrolytes
Buzz word: “rice-water stools” (rice is mucus and puss along with tons of clear liquid, no solids coming out anymore)
47
vibrio cholera virulence
Organisms adhere to intestinal mucosa of small intestine:
- secrete cholera toxin
- Cholera toxin: phage mediated, ctxA and ctxB
48
vibrio cholera complications
Huge volume loss, can die from dehydration in 12 hours
49
Vibrio parahaemolyticus characteristics
Shellfish are natural reservoirs (Oysters)
| More common in southeast US (Gulf Coast)*
50
Vibrio parahaemolyticus virulence
*produces an enterotoxin
thermostable direct hemolysin (Kanagawa hemolysin)
Induces chloride secretion by increasing intracellular calcium
51
Vibrio parahaemolyticus symptoms
Incubation: 5-72 hours
| Explosive, watery diarrhea
52
Vibrio parahaemolyticus lab diagnostics
TCBS - thiosulfate citrate bile salts sucrose agar
-green agar that turns orange when Vibrios grow
53
campylobacter jejuni characteristics
Gram (-) curved/spiral rod
- Microaerophile
- Capnophilic – likes CO2
* contaminated chicken food products!
* *leading cause of bacterial gastroenteritis in US (she repeated this 3 times – this is more common than salmonella – so when you consume raw eggs you're more likely to get campylobacter than salmonella)
1.4 to 2 million infections/annually in U.S.
54
campylobacter jejuni transmission
- ingestion of contaminated food, poultry, milk or water
| - requires a large dose due to susceptibility to stomach acid
55
campylobacter jejuni lab diagnostics
Prefers 42C – higher than body temp – isolate in lab by putting on two plates 42 vs. 37 (only survives on one)
56
campylobacter jejuni virulence
C. jejuni invades epithelium of small intestine, causes inflammation
57
campylobacter jejuni symptoms
- bloody diarrhea
- fever
- abdominal pain
58
campylobacter jejuni complications
Associated with Guillain-Barré syndrome:
- Autoimmune disorder of the peripheral nervous system
- Antigenic cross reactivity of LPS and gangliosides
* antibodies cross react with peripheral nervous system (thinks its getting rid of campylobacter, but its attacking itself instead)
Reactive arthritis
- painful inflammation of the joints
* antibodies cross react with joints (BUT NO INFECTION IN the joint!)
59
Helicobacter pylori characteristics
```
Spiral shaped curved rod
As culture ages, changes shape
*Gram negative (has LPS)
Can live in the stomach! (Acidophile!)
Microaerophile
Fastidious
```
70-90% of the population in developing countries has H. Pylori
60
Helicobacter pylori virulence
*Urease - produces cloud of ammonia that neutralizes the stomach acid
flagella - allow for invasion of stomach mucosa
- Block acid production
- Neutralize acid with ammonia
- Burrow into mucus
- Attach to epithelial cells
61
Helicobacter pylori symptoms
Fullness
Vomiting
Nausea
Hypochlorhydria (increases your risk of infection):
– people with a decrease in stomach acid (those using tums/antacid/Nexium (purple pill) – ahh **bacterial infection that is directly linked to cancer!
62
Giardia lamblia transmission
- Streams, lakes
- wild and domestic animals
- Contaminated water, fruits and vegetables
need to ingest: (10-25 cysts)
63
Giardia lamblia symptoms
Incubation: 1-4 weeks (average is 10 days)
*Acute, onset of foul smelling, watery *diarrhea
cramps
flatulence
*steatorrhea.
duration:: 10 to 14 days
64
Giardia lamblia characteristics
-Protozoa (2 stages!)
-Cysts (resistant stage)
Typically shed in stools
Infective stage
Spread by fecal-oral route
-Trophozoites (active stage)
Live in the intestine
65
Giardia lamblia virulence
Gastric acid causes change from cyst to trophozoite
Trophozoite attaches to intestinal villi
Localized tissue damage
66
Giardia lamblia diagnosis
Diagnosis:
| -microscopy of stool sample, 1/day for 3 days
67
Shrigella and Enterohemorrhagic (EHEC) e coli. are both quite infective
10 cells : shrigella
| 10 - 100 cells: EHEC
