Diarrhea Flashcards
1
Q
• Acute watery diarrhea is main feature of…
A
viral gastroenteritis
2
Q
two main causes of viral gastroenteritis?
A
norovirus, rotavirus
3
Q
tx for viral gastroenteritis
A
fluids
no abx
4
Q
which two viral gastroenteritis causes are part of the calciviridae family?
A
norovirus and sapovirus
5
Q
How is norovirus diagnosed?
A
RT-qPCR Assay (sensitive and specific)
ELISA (outbreak only)
6
Q
how is rotavirus diagnosed?
A
RT-qPCR Assay (sensitive and specific)
7
Q
Which bacterial family has the following morphology?
Aerobic, facultative anaerobic
Gram negative rods
A
enterobacteriaceae
8
Q
These are four characteristics of…
• Most ferment carbohydrates to lactic acid
- Flagella (H antigen)
- Capsule (K or Vi)
- LPS (O antigen)
A
enterobacteriaceae
9
Q
Three important species of enterobacteriaceae
A
salmonella, shigella, e. coli
10
Q
Most members of enterobacteriaceae are motile with what type of flagella?
A
peritrichous
11
Q
is shigella motile?
A
no
12
Q
enterobacteriaceae typically have what two virulence factors?
A
endotoxin
capsule
13
Q
enterobacteriaceae endotoxin is a __________ component of LPS, it can lead to septic shock
A
Lipid A
14
Q
This mechanism is widely used by gram - bacteria like enterobacteriaceae that can “inject” material into host cell to alter protein expression
A
T3SS (type 3 secretion system)
15
Q
important species of salmonella that can infect humans…
A
s. enterica
16
Q
Primary source of salmonella transmission?
A
ingestion of contaminated food/water
17
Q
Secondary source of salmonella transmission
A
animals
18
Q
typing of salmonella depends on what two antigens?
A
flagellar H antigen
LPS O antigen
19
Q
What percent of patients with salmonella gastroenteritis develop bacteremia?
A
5%
20
Q
This serovar of salmonella is a generalist that infects a variety of hosts causing self-limiting gastroenteritis
A
S. typhimurium
21
Q
This is the most common clinical isolate of salmonella enterica…
A
S. enterica serovar enteritidis
22
Q
What type of T3SS is present with salmonella?
A
SPI1
23
Q
Does E. coli have SPI-1?
A
no
24
Q
Salmonella leads to what type of changes in epithelial cells?
A
actin and cytoskeletal changes
engulfment of bacterium
25
Salmonella transits the epithelial cells to and replicates inside _______ to gain access to systemic sites...
macrophages
26
What are three clinically relevant strains of E. coli?
ETEC: enterotoxigenic
EHEC: enterohemorrhagic
EIEC: enteroinvasive
27
Which type of e. coli?
watery diarrhea/intestinal cramps. Travelers diarrhea
1-2 days post-exposure
lasts 3-5 days
ETEC
28
What are two ETEC virulence factors?
LT1 - heat labile toxin
STb - heat stabl toxin
29
Which ETEC toxin activates adenylate cyclase leading to increased cAMP and Cl- into the intestinal lumen?
LT1 - heat labile
30
Which ETEC toxin binds guanylate cyclase leading to increased cGMP?
STb - heat stable
31
This type of e. coli:
- common foodborne illness
- also called STEC (shiga toxin producing E. Coli)
- O157:H7
- cattle reservior
EHEC
32
Stx binds to what receptor present on human intestines?
globotriaosylceramide receptor
33
What type of toxin is Stx toxin, stopping protein synthesis and cytokine production?
A-B toxin
34
Stx is not released in an T3SS... so how is the toxin released?
lysogenic bacteriophage lysis
35
What are two virulence factors present with EHEC?
intimin (adhesin)
Tir (cytoskeletal effects)
36
This type of e. coli:
- profuse, bloody diarrhea, dysentery
- 12 to 72 hour incubation period
- no flagella, no adherence factors
EIEC
37
EIEC is basically the same as...
shigella
38
what differentiates shigella from other pathogenic e. coli?
lac -
39
What is the most common shigella type, and what is the most virulent?
MC: S. sonnei
most virulent: S. dysenteriae
40
What pathogen?
Can range from mild watery diarrhea to severe dysentery with blood and mucus
1 to 3 day incubation
Shigella
41
What is the initial feature of shigella associated with toxin?
watery diarrhea
42
How does shigella leave the gut?
Macrophage cells or dendritic cells engulfment
43
Shiga toxins are produced by which type only, and are encoded by...
S. dysenteriae
encoded by Stx phage
44
Which shiga toxin?
very potent
identical to shiga-like toxin on O157:H7
Shiga toxin 1
45
Shiga toxin 2 is the same as shiga toxin 1 except 2 changes...
structure, immunogenic
46
What causes dysentery with shigella infection?
toxins
47
Which two toxins are carried by other shigella species, but are generally less severe...
shet1 and shet2
48
What is the route of infx for shigella?
fecal-oral
49
how many shigella cells can cause disease?
10
50
Which bacterial causes of diarrhea are G- and lac-
shigella, salmonella
51
Which bacterial cause of diarrhea produces H2S on HE/TSI or SS Agar
salmonella
52
What type of media is used to identify diarrhea cause?
maconkey agar
53
Which pathogen?
Lac+, H2S-
E. Coli
54
Which pathogen?
Lac-, H2S+
Salmonella
55
Which pathogen?
Lac-, H2S-
shigella
56
How do you treat shigella, salmonella, e. coli? Why no abx?
supportive care
abx prolong infx
57
5% of salmonella is resistant to how many drugs?
5 or more
58
What can cause D+ HUS from shigella and e. coli?
Abx
59
What pathogen?
G- curved rod
acid sensitive, large numbers must be ingested
Vibrio cholerae
60
What toxin?
A-B toxin
causes high cAMP, Cl- secretion
Sodium, water follow Cl- into lumen causing diarrhea
Cholera toxin
61
What disease?
profuse watery diarrhea
enormous bacterial load
severe dehydration, organ failure, death
Cholera
62
How is cholera diagnosed?
stool cx
63
How is cholera treated?
oral rehydration
64
when are abx used with cholera?
severe cases
65
What disease?
```
• Diarrhea: loose, watery stools for
several days
• Fever
• Nausea
• Colitis, pseudomembranous colitis
```
C. diff
66
What pathogen?
G+ obligate anaerobe
endospore forming
A & B toxins that disrupt actin and cause pseudomembranes
C. diff
67
What patients primarily get infected by c. diff?
hospitalized on abx
68
The below are risk factors for...
65 and older who take antibiotics and receive medical care
• Extended hospital and nursing homes stays
• People with weakened immune systems
c. diff
69
What drug can increase risk for c. diff in hospitalized patients?
PPIs
70
If possible, what tx should be stopped in order to prevent c. diff?
abx
71
why does c. diff usually recur even after vanco or metronidazole administration?
endospores
72
What process reliably kills endospores?
autoclave
73
This bacteria has the following characteristics:
- microaerobic (10% co2, 80% N2, 10& o2)
- G- s-shaped rod
campylobacter
74
What is the most common cause of gastroenteritis in the US?
C. jejuni (campylobacter)
75
What virulence factor present on campylobacter has the following characteristics?
* Provides serum resistance
* Attachment to host cells
* Invasion of epithelial cells
capsule
76
What is the infectious dose of campylobacter?
500-1000 cells (low)
77
What pathogen can cause the below?
* Self-limiting gastroenteritis
* Diarrhea (sometimes bloody), fever, severe abdominal pain
* Typically lasts about a week
campylobacter
78
What is a rare complication from C. jejuni that causes symmetric weakness over several days, with recovery over months?
Guillain Barre
79
Campylobacter LOS resembles _______ which leads to Ab cross reactivity and Guillain Barre
neuronal gangliosides
80
The below are methods of diagnosing...
Microscopy (s-shaped rods)
campy antigen detection
cx with TMP
C. jejuni
81
Which organism?
* motile, flagellated spiral shaped
* Oxidase positive
* Catalase positive
H. pylori
82
H. pylori produces _____ which allows it to produce ammonia to survive HCl in gastric environment
urease
83
What H. Pylori virulence factor?
-forms pores in host membranes
VacA
84
What H. Pylori virulence factor?
higher incidence of gastric cancer...
CagA
85
three methods to dx h. pylori...
Gastric biopsy + urease test (invasive)
polyclonal Ab detection (easy, inexpensive)
Cx (difficult)
86
is h. pylori treated with abx? what can occur as a result?
yes, c. diff risk
87
Which pathogen?
Gastroenteritis
• Septicemia
• Clostridial myonecrosis (Gas gangrene)
• up to 12 toxins
clostridium perfringens
88
The following describes pathogenesis of which organism?
• Ingestion of contaminated meat
– Allowing food to cool to below 60°C allows spore germination
– Reheating to 75°C kills enterotoxin
c. perfringens
89
Sxs of c. perfringens occur due to...which means what for its incubation?
toxins, short incubation (self-limiting)
90
Three important species of bacillus...
B. subtilis, B. cereus, B. anthracis
91
What pathogen has the following characteristics?
G+ rod, forms chains
Aerobic, facultative anaerobe
spore forming
Bacillus
92
Bacillus species are responsible for producing what type of compounds used by humans?
(antimicrobials, insecticides)
bacitracin
polymyxin B
Bt toxin
93
Bacillus cereus can cause emetic disease and diarrheal disease. What toxin is responsible for each?
emetic: heat stable enterotoxin
diarrheal: heat labile enterotoxin (similar to cholera)
94
Emetic disease from bacillus cereus is frequently caused by...
Intoxication from eating contaminated rice
95
If disease is toxin mediated, is there fever?
no
96
What is a common cause of bacillus cereus diarrheal disease?
eating contaminated meat/veggies
97
What pathogen?
G+ cocci
Catalase +
staphylococcus
98
What pathogen?
non-motile
optimal growth 30-37 C
can grow between 15-40 C
Staphylococcus
99
Staph. Gastroenteritis is caused by...
staphylococcal superantigens
100
list the Staphylococcal superantigens
SEA, SEB, SEC...through SER
101
What is responsible for food poisoning from staph?
staphylococcal enterotoxins
102
What are two important characteristics of staphylococcal enterotoxins?
heat labile
| resistant to gastric enzymes
103
describe the onset of food poisoning by staph
4 hours onset
