Exam 3 Lecture 20 Flashcards
1
Q
Where can pathogenic E. coli come from?
A
Ingesting undercooked or contaminated meat; contaminated sprouts
2
Q
True or false: pathogenic E. coli frequently causes disease in both cows and humans
A
False: not usually in cows
3
Q
Which Enterobacteriacae spp are found as normal microbiota? (5)
A
- E. coli non-pathogenic species
- Klebsiella
- Enterobacter
- Proteus
- Serratia
4
Q
Examples of E. coli non-pathogenic species + what do they produce
A
E. coli K12, E. coli B; produce vitamin K, which is important for production of RBC
5
Q
What Enterobacteriacae spp are not part of normal human microbiota? (4)
A
- Salmonella
- Shigella
- Yersinia
- Pathogenic E. coli
6
Q
What kinds of diseases can pathogenic Enterobacteriacae cause?
A
endotoxic shock, UTI, diarrhea, hemolytic uremic syndrome
7
Q
Describe gram stain of E. coli
A
gram negative bacilli
8
Q
E. coli can ferment ___ and are ___-positive
A
lactose; indole
9
Q
True or false: E. coli is the most common Enterobacteriacae in normal colonic flora
A
true
10
Q
What infections can pathogenic E. coli cause?
A
UTI, gastroenteritis, septicemia, neonatal meningitis
11
Q
True or false: shigatoxin must be present to cause UTI and gastroenteritis
A
false; these can be caused by E. coli in our microbiota
12
Q
E. coli is usually grown on ____ ___
A
MacConkey agar
13
Q
MacConkey agar characteristics
A
phenol agar, sugars, lactose, salts
14
Q
On a MacConkey agar, if able to produce ___-______, the bacteria will metabolize ____, causing the medium to turn ___ in color.
A
beta-galactosidase; lactose; pink
15
Q
What are the 6 types of pathogenic E. coli?
A
- Enterotoxigenic E. coli (ETEC)
- Enteropathogenic E. coli (EPEC)
- Enteroinvasive E. coli (EIEC)
- Enterohemmorhagic E. coli (EHEC)
- Enteroaggregative E. coli (EAEC)
- Diffuse Aggregative E. coli (DAEC)
16
Q
True or false: 6 types of pathogenic E. coli are easily distinguishable by appearance and biochemical tests
A
false - not easily distinguishable
17
Q
Name some surface structures of E. coli
A
cell wall, K antigen capsule, pili (lots of dif types), H antigen flagella
18
Q
BFP Pili
A
bundle forming pili found in EPEC strains
19
Q
CFA Pili
A
colonization factor antigen; pili used by ETEC strains for binding to host cells
20
Q
Type I pili
A
common pili binds via FimA to mannose residues on epithelial cells
21
Q
What do O and H refer to in E. coli O157:H7?
A
O = O antigen in LPS H = flagellar antigen
22
Q
True or false: all 6 pathogenic strains of E. coli have similar mechanisms of infection
A
false; they are different
23
Q
EPEC mechanism of diarrheal disease
A
BFP pili used to form cluster of cells, injects effector proteins, causes pedestal formation
24
Q
EHEC mechanism of diarrheal disease
A
causes pedestal formation and injects Stx-shiga toxin into the cells
25
ETEC mechanism of diarrheal disease
uses CFA pili to bind and then secretes two types of enterotoxins - ST (heat stable) and LT (heat labile)
26
EAEC mechanism of diarrheal disease
forms a biofilm on the surface of the cells, produces cytotoxins and enterotoxins to cause diarrhea
27
EIEC mechanism of diarrheal disease
binds and invades cells, then escapes into the cytoplasm similar to Shigella
28
DAEC mechanism of diarrheal disease
binds as single cells
29
Which E. coli is one of the major causes of UTIs?
UPEC (uropathogenic E. coli)
30
UPEC is responsible for ____% of the ____ cases of UTIs and ____ cases of pylonephritis (kidney infection)
70-90%; 7 million; 250,000
31
How does UPEC infection start?
spread of UPEC bacteria from the colon to the bladder
32
True or false: UPEC strains are often nosocomial acquired
false; more so community acquired (sexual transmission), but unclear what the mechanism of pickup is
33
The presence of _-___ in UPEC is associated with pyelonephritis
P-pili
34
Pyelonephritis
kidney infection caused by spreading of UTI from urethra/bladder to the kidneys
35
What is FimH?
protein at tip of P-pili which is responsible for the binding of the pilus to the host cell via mannose receptor
36
True or false: Pili and FimH mutants do not adhere well to bladder cells
True
37
What did researchers find in the UPEC low flow/high flow rate experiment?
The faster the flow rate, the more tightly FimH binds to mannose, suggesting that the bacteria have found a way to prevent from being excluded during fecal/urinary flow
38
Where is ETEC most prevelent?
developing world
39
ETEC is a major cause of ____ ___ and ____ ____
traveller's diarrhea; infantile diarrhea
40
How does ETEC spread?
through contaminated food (fecal/oral route)
41
True or false: low inoculum of ETEC is sufficient to cause disease
false - requires high inoculum
42
ETEC attacks the ___ ___, which causes watery diarrhea
small bowel (part of small intestine)
43
True or false: ETEC does not cause histological or inflammatory changes of the GI tract
true
44
ETEC treatment
hydration
45
ETEC toxins are found on ......
plasmid
46
ETEC enterotoxins include:
1. LT (heat labile toxin)
2. ST (heat stable toxin)
** good mnemonic ** (LT = heat LABILE; ST = heat STABLE)
47
Features of ETEC LT1
similarity to cholera toxin, causes cAMP mediated osmotic disruption of the cell
48
```
Which of these ETEC enterotoxins have a known mechanism of disease?
A. LT1
B. LT2
C. STa
D. STb
```
A and C
49
Where is EPEC most prevalent?
developing world
50
EPEC attacks ___ ___
small bowel
51
EPEC causes:
severe watery diarrhea, nausea, vomiting, dehydration
52
EPEC treatment
hydration
53
EPEC initially adheres to host cell via ___ ___. This forms an intimate attachment and allows ___ ____ and ____ _____.
BFP pili; actin condensation; microvillous effacement
54
EPEC attaches to enterocytes, causing loss of_____.
microvilli
55
What type of secretion system does EPEC use? What does EPEC secrete and why?
Type III SS; secretes effector proteins in order to rearrange host actin and form pedestal
56
EPEC causes "_____ __ ____" lesions along with pedestal formation to allow close association to host cell
attaching and effacing lesions
57
Once EPEC adheres to host cell, it injects ___, which is a needle complex that serves as a translocation tube.
EspA
58
What protein does EPEC secrete via EspA?
Tir
59
When Tir protein is injected into host cell, Tir is translocated into the ____ and then reappears on ____ of the host cell
cytoplasm; surface
60
____ binds to Tir protein to form a tight complex between EPEC and host cell.
Intimin (EaeA)
61
Mechanism of EPEC induced diarrhea (more specific in terms of cellular response)
1. EPEC binds via BFP pili, causing loss of absorptive surfaces (malabsorption)
2. alters Cl- or HCO3- ion secretion
3. decreases the integrity of tight junctions
4. neutrophil recruitment leads to more tissue damage
5. more water flow out due to decreased resistance
62
EHEC is the cause of ____ diarrhea
bloody
63
EHEC can cause ____ ____ ____
hemolytic uremic syndrome (HUS)
64
True or false: regarding EHEC, ~100 organisms is enough to cause infection
True
65
EHEC is very resistant to ___
acid (thus can survive acidity of stomach)
66
What are the two major virulence factors of EHEC?
1. adhesins
| 2. Shiga Toxins
67
EHEC adhesins are encoded on:
LEE plasmid (pathogenicity island)
68
EHEC Shiga-like toxins can enter the _____ and cause microvascular damage in the ___ and ___
bloodstream; brain and kidney
69
EHEC produces Shiga-like toxins are called:
Stx-1 and Stx-2
70
True or false: Stx-1 and Stx-2 are encoded on a bacteriophage and undergo lysogenic/lytic phases
True
71
What induces lysogenic to lytic transition of EHEC Shiga-like toxins?
Antibiotics or DNA damage
72
True or false: EHEC causes attaching and effacing lesions and has Intimin
True
73
True or false: Antibiotics and DNA damage can induce horizontal gene transfer (conjugation) in EHEC
True
74
Shiga-like toxins block ___ ___, which leads to cell death of the ______ ____ in the kidney.
protein synthesis; microvascular system
75
Stx-2 has a role in the development of ___
HUS
76
Most common source of EHEC in the US:
cattle
77
True or false: almost all cattle in feed lots are positive for EHEC-contamination of ground beef
True (99%!!)
78
How do we diagnose EHEC?
detection of Shiga-like toxin and enrichment culture (this can be tough, but PCR is available)
79
True or false: important treatment of EHEC is via antibiotics
False!! (super false omg)
| -antibiotics induce lysogenic to lytic phase, causing more shiga-like toxin to be produced
80
True or false: EAEC makes a biofilm on top of cells
true
81
EAEC causes ___ diarrhea via attacking the ___ ___
watery; small bowel
82
In immunocompromised patients, EAEC causes:
chronic persistent diarrhea
83
What is unique about EIEC in how it interacts with the host cell and causes disease? (3)
1. invades intestinal cell
2. multiples within the cell
3. spreads to adjacent cells
84
Where is EIEC most common?
developing world
85
EIEC attacks:
large bowel
86
True or false: EIEC causes watery diarrhea that progresses to bloody diarrhea
True
87
EIEC causes disease similar to ___, but it is usually ___
Shigella; milder
88
True or false: some suggest that shigella and EIEC are the same organism, just different LPS
true
89
___ and Shigella use the same set of genes for invasion
EIEC
90
EIEC causes ____ ____ ____, then ___ and becomes intracellular
attaching + effacing lesions; invades
91
When EIEC invades and it becomes intracellular, it is trapped inside a ____. In order for EIEC to spread to adjacent cell, EIEC must:
phagosome; EIEC must lyse vacuole to allow intracellular movement
92
Shigella reservoir
human gastrointestinal tract
93
Shigella causes ____ cases/year of diarrhea
more than 200 million
94
Shigella is highly ____. Less than ___ organisms are sufficient to cause infectious disease.
contagious; 10
95
What are the 4 serogroups of Shigella?
Group A: Shigella dysenteriae
Group B: Shigella flexneri
Group C: Shigella boydii
Group D: Shigella sonnei
96
How do we diagnose Shigella?
detection of antigen
97
True or false: Groups A, B, and C of Shigella cannot be distinguished physically.
False: biochemically
98
Shigella and Salmonella are grown on:
Hektoen Enteric Agar
99
Shigella appears ___ on agar, whereas Salmonella appears ___.
light; black
100
Severity of Shigella disease depends on ____
serogroup
101
Which Shigella spp cause more severe disease?
S. dysenteriae and S. flexnari
| Groups A & B
102
Which Shigella spp causes milder disease? What are the symptoms?
S. sonnei; watery diarrhea instead of dysentery (bloody diarrhea)
103
True or false: Shigella can survive well in blood and macrophages
False - rare to find bacteria in the blood
104
Shigella can be shed via stool for up to _ ___ after infection while you are asymptomatic
6 weeks
105
What complication can follow Shigella infection?
Hemolytic Uremic Syndrome (HUS)
106
Most Shigella cases occur in:
children (especially in institutions or day cares)
107
Is there a vaccine available for Shigella?
No
108
Shigella can tolerate:
acid
109
Shigella invades ____ ___ and leads to ____ and ____
large bowel; ulceration and abscesses
110
True or false: Shigella has a virulence plasmid
True
111
Shigella virulence plasmid includes:
invasion loci and T3SS
112
True or false: Shigella maintains its plasmid when grown in culture
False: somehow plasmid is lost when grown in culture
113
All strains of Shigella produce ____
enterotoxins (minor contributors to disease except for S. dysenteriae which produces Shiga toxin)
114
Shiga toxin is present in:
S. dysenteriae and on a phage
115
Shiga toxin is similar to the Shiga-like toxin of ___
EHEC
116
True or false: Shiga toxin is necessary for invasion
false
117
Shiga toxin can cause disease from a ____
distance
118
What kind of toxin is the Shiga toxin? (hint: what are its components)
bipartite (A-B toxin)
119
Mechanism of Shiga toxin
1. A-B toxin secreted by Shigella and binds to Gb3 glycolipid
2. Shiga toxin is internalized and transported to the golgi
3. A-subunit is released into the cytoplasm
4. A-subunit binds to A-site of ribosome and blocks tRNA binding
120
Regarding Shiga Toxin, inhibition of protein synthesis causes damage in:
kidney, brain, intestine
121
Shiga toxin can infect kidney cells, which may cause damage in the ____ ____ of the kidneys. This can cause ___ to adhere to ____ deposits at the site of damage, which reduces kidney function.
filtration apparatus; platelets; fibrin
122
True or false: Shigella can kill macrophages
True
