Escherichia coli Flashcards
1
Q
What is the most common facultative anaerobe in the human gastrointestinal tract?
A
E. coli
2
Q
T/F. E. coli is always pathogenic.
A
False
3
Q
What are two key characteristics of E. coli related to motility and metabolism?
A
- Motile
- Lactose fermenters
4
Q
How do E. coli acquire virulence factors?
A
Horizontal gene transfer
5
Q
What are the main pathotypes of diarrheagenic E. coli (DEC)?
A
- Enterotoxigenic E. coli (ETEC)
- Enteropathogenic E. coli (EPEC)
- Shiga toxin-producing E. coli (STEC/EHEC)
- Enteroaggregative E. coli (EAEC)
- Enteroinvasive E. coli (EIEC)
6
Q
What are the two additional enteric pathotypes of E. coli?
A
- Diffusely adherent E. coli (DAEC)
- Adherent-invasive E. coli (AIEC)
7
Q
ETEC
How is Enterotoxigenic E. coli (ETEC) transmitted?
A
Ingestion of contaminated water or food
8
Q
ETEC
Who is most affected by ETEC infections?
A
- Children in developing countries
- Returning travelers
9
Q
ETEC
How do foodborne outbreaks of ETEC occur in developed countries?
A
Improper sanitation
10
Q
ETEC
What is the first step in ETEC pathogenesis?
A
Adherence and colonization of small intestine mucosa, mediated by adhesins or colonization factors
11
Q
ETEC
What are the types of colonization factors (CFs) in ETEC?
A
- Chaperone-usher type pili
- Type IV pili
- Thinner fibrillae
- Afimbrial factor
12
Q
ETEC
What are examples of nonpilus adhesins involved in ETEC adherence?
A
Tia, TibA, and EtpA
13
Q
ETEC
What toxin produced by ETEC shares a nearly identical structure and mechanism with cholera toxin?
A
Heat-labile enterotoxin (LT)
14
Q
ETEC
What is the result of LT-mediated GαS activation?
A
- Increased cAMP
- Activation of protein kinase A (PKA)
- Stimulation of CFTR
- Chloride secretion and sodium and water loss
15
Q
ETEC
This toxin is produced by 75%-80% of ETEC isolates and is associated with more severe disease than LT-only producing strains.
A
Heat-stable enterotoxin (ST)
16
Q
ETEC
What is the traditional mechanism of ST-mediated pathogenesis?
A
- Increased cGMP
- Activates protein kinase G (PKG)
- Stimulates CFTR
- Chloride secretion and sodium and water loss
17
Q
ETEC
What diagnostic methods can confirm ETEC diarrhea?
A
- Immunoassays
- PCR assays
- DNA probe assays (for toxins)
18
Q
ETEC
What antibiotic therapies are effective in shortening the duration of traveler’s diarrhea caused by ETEC?
A
- Azithromycin
- Levofloxacin
- Rifaximin
19
Q
EPEC
How is EPEC classified?
A
- Typical EPEC (tEPEC): contains type IV bundle-forming pili (BFP)
- Atypical EPEC (aEPEC): Lacks BFP
20
Q
EPEC
How soon after ingestion can EPEC diarrhea start?
A
As early as 3 hours
21
Q
EPEC
Which age group is most affected by tEPEC?
A
Infants aged 0-11 months
22
Q
EPEC
How is EPEC transmitted?
A
Person-to-person contact
23
Q
EPEC
Where are EPEC outbreaks commonly seen?
A
- Nosocomial settings
- Childcare centers
24
Q
EPEC
What are the primary symptoms of EPEC infection?
A
- Watery, nonbloody diarrhea
- Vomiting
25
# EPEC
What role does BFP play in tEPEC adherence?
Aids in biofilm formation and retraction
26
# EPEC
Where are attaching and effacing (A/E) lesions formed?
On the apical surface of intestinal epithelial cells
27
# EPEC
What genetic locus regulates A/E lesion formation in EPEC?
The locus of enterocyte effacement (LEE).
28
# EPEC
What key virulence factors are encoded by the LEE?
* T3SS
* Intimin
* Translocated intimin receptor (Tir)
* EPEC-secreted proteins (Esp)
29
# EPEC
What is the role of EspA in EPEC adhesion?
Forms filamentous extension of T3SS, sonnecting it to the host cell
30
# EPEC
Leads to microvilli loss and actin pedestal formation.
Tir
31
# EPEC
What proteins form pores in the host cell membrane for Tir insertion?
EspB and EspD
32
# EPEC
How does EPEC disrupt the host immune response?
By inhibiting the NK-κB pathway.
33
# EPEC
It participates in protein-protein interactions affecting intestinal barrier function.
EspF
34
# EPEC
They inhibit luminal chloride transport.
EspG and EspG2
35
# EPEC
How does EPEC contribute to malnutrition in prolonged disease?
It inhibits thiamine uptake
36
# EPEC
What rapid diagnostic test is available for EPEC in low-income countries?
Rapid agglutination test specific to EspB
37
# EPEC
Whats a measure that helps prevent EPEC infection?
Human breast milk
38
# EPEC
How does human breast milk help prevent EPEC infection?
It contains antibodies against BFP, intimin, EspA, EspB, and O antigens
39
# STEC/EHEC
What are the main symptoms of STEC infection?
Watery, often bloody diarrhea, which can lead to hemolytic-uremic syndrome
40
# STEC/EHEC
What is the leading cause of renal failure in children?
Hemolytic-uremic syndrome (HUS)
41
# STEC/EHEC
What are the three key features of HUS?
* Anemia
* Thrombocytopenia
* Renal failure
42
# STEC/EHEC
What complications can arise from thrombosis in HUS?
* Ischemic bowel
* Peripheral necrosis
* Neurologic complications
43
# STEC/EHEC
What are the potential long-term sequelae of HUS?
* Cardiac
* Renal
* Gastrointestinal
* Neurologic
* Endocrine
44
# STEC/EHEC
What is the primary natural reservoir for STEC?
Cattle
45
# STEC/EHEC
What are common sources of STEC infection?
* Undercooked beef
* Contaminated water
* Contaminated beverages
46
# STEC/EHEC
How can fecal-oral transmission of STEC occur?
* Farm animal exposure
* Petting zoos
* Person-to-person contact
47
# STEC/EHEC
When does bloody diarrhea typically develop in STEC infection?
Around 2 days after infection
48
# STEC/EHEC
What are the two types of Shiga toxins produced by STEC?
Stx1 and Stx2
49
# STEC/EHEC
What organelle is inhibited by shiga toxin?
Ribosomes
50
# STEC/EHEC
Besides inhibiting ribosomal function, how else does Shiga toxin affect host cells?
Affects cell signaling, promoting inflammation and apoptosis
51
# STEC/EHEC
How does Shiga toxin spread through the bloodstream?
Binding to leukocytes
52
# STEC/EHEC
What type of lesions does EHEC produce on intestinal cells similar to EPEC?
Attaching and effacing (A/E) lesions
53
# STEC/EHEC
What key virulence factors are encoded by the LEE in EHEC?
* T3SSS
* Intimin
* Tir
* Esp
54
# STEC/EHEC
What molecular techniques can be used to detect STEC?
PCR assays and immunoassays
55
# STEC/EHEC
Why is antibiotic therapy not recommended for STEC infections?
It may increase the risk of HUS
56
# EAEC
In which regions is EAEC a major cause of diarrhea?
Both developed and developing countries
57
# EAEC
How is EAEC primarily transmitted?
Fecal-oral route
58
# EAEC
What conditions are associated with EAEC infection?
* Foodborne outbreaks
* Traveler's diarrhea
* Postinfectious irritable bowel syndrome
59
# EAEC
What populations are at higher risk for chronic diarrhea due to EAEC?
Children and HIV patients
60
# EAEC
What type of mucosal damage does EAEC infection cause?
Microvilli loss and cell death
61
# EAEC
What inflammatory marker is elevated in EAEC diarrhea?
IL-8
62
# EAEC
What type of adhesion mechanism is linked to EAEC?
Aggregative adherence, mediated by fimbriae (AAF)
63
# EAEC
T/F. EAEC strains form thick biofilms on both intestinal mucosa and abiotic surfaces.
True
64
# EAEC
Biofilms can harbor bacteria in dense aggregates, interfering with...
Host nutrient absorption
65
# EAEC
What are the key toxins produced by EAEC?
* EAST-1
* Plasmid-encoded enterotoxin (Pet)
66
# EAEC
Protein structurally similar to ETEC toxins, increasing cGMP levels.
Enteroaggregative heat-stable enterotoxin 1 (EAST-1)
67
# EAEC
SPATE family toxin that causes intestinal crypt dilation and cell damage.
Plasmid-encoded enterotoxin (Pet)
68
# EAEC
What laboratory tests are commonly used to detect EAEC?
* Clump-formation tests
* Tissue culture adhesion assays
69
# EAEC
What molecular methods can help diagnose EAEC?
PCR and DNA probes
70
# EIEC
What bacterial pathogen shares a similar pathogenesis with EIEC?
Shigella
71
# EIEC
What are the key biochemical characteristics of EIEC, making it similar to Shigella?
* Non-motile
* Lactose non-fermenting
* Lysine descarboxylase negative
72
# EIEC
How does EIEC infection compare clinically to shigellosis?
Indistinguishable
73
# EIEC
How does the infectious dose of EIEC compare to Shigella?
The inoculum required is higher
74
# EIEC
What are the initial symptoms of EIEC infection?
Watery stools, which may progress to dysentery
75
# EIEC
Who is most commonly affected by EIEC dysentery?
Children in developing world
76
# EIEC
How do EIEC outbreaks occur in developed countries?
* Person-toperson transmission
* Foodborne outbreaks
77
# EIEC
What foods are commonly associated with EIEC outbreaks?
Contaminated cheese, milk products, and beef
78
# EIEC
What plasmid mediates EIEC invasion?
plnv
79
# EIEC
What virulence mechanism does pInv encode?
T3SS
80
# EIEC
What are the two key functions of the T3SS in EIEC?
* Escape phagocytosis
* Invasion of intestinal epithelial cells
* Cell-to-cell spread
81
# EIEC
T/F. EIEC causes cell-to-cell spread using the host actin-filament machinery.
True
82
# EIEC
What historical test was used to identify Shigella and EIEC?
The Sereny test, which observed keratoconjunctivitis in guinea pigs.
83
# EIEC
What modern methods are used to diagnose EIEC?
* PCR
* Biochemical assays
* Multilocus sequence typing (MLST) analysis
84
# DAEC
What type of diarrhea is caused by DAEC infection?
Watery diarrhea
85
# DAEC
Which age group is primarily affected by DAEC?
Older children
86
# DAEC
What adherence pattern is characteristic of DAEC?
Diffuse adherence (DA), associated with fimbrial and afimbrial adhesins from the Afa/Dr family.
87
# DAEC
What does Afa/Dr+ adhesins bind to on epithelial cells?
Human decay-accelerating factor (DAF) on the brush border.
88
# DAEC
What cellular effects result from DAEC binding to DAF?
* Increased permeability
* Cytoskeletal changes
* Defective brush border proteins
* Microvilli loss
89
# DAEC
What potential role does DAEC play in Crohn’s disease (CD)?
DAEC has been found in CD patients, where increased DAF expression is observed.
90
# DAEC
What toxins are expressed by diarrheal DAEC strains?
* EAST-1 (Enteroaggregative heat-stable enterotoxin 1)
* ShET1 (Shigella enterotoxin 1)
* Hemolysin
91
# DAEC
How does DAEC flagellar stimulation contribute to inflammation?
* TLR5 activation induces IL-8 secretion.
* Leads to neutrophil migration and inflammation.
* Further promotes DAF expression.
92
# AIEC
T/F. AIEC expresses traditional DEC virulence factors
False
93
# AIEC
What fimbriae facilitate AIEC adherence?
* Type I fimbriae
* Long polar fimbriae (LPF)
94
# AIEC
What host structures do AIEC fimbriae target?
* M cells on Peyer patches
* CEACAM6 on intestinal epithelial cells
95
# AIEC
This is a membrane-bound protein, promotes fusion of outer membrane vesicles (OMVs) with Gp96, a host ER stress response chaperone.
OmpA
96
# AIEC
Where is Gp96 overexpressed?
In the ileum of Crohn’s disease patients.
97
# AIEC
What happens after AIEC invades the lamina propria?
* It replicates in macrophages
* Induces TNF-α production
* Does not provoke macrophage death
