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DTMH Block 3 > Intestinal diseases > Flashcards

Intestinal diseases Flashcards

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1
Q

What is the leading cause of morbidity and mortality worldwide?

A

Gastroenteritis

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2
Q

Where are infectious intestinal diseases usually contracted in the UK?

A

Home

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3
Q

Compare paediatric diarrhoea in developed vs developing countries

A

Developed
- <1 episode/y
- winter
- rare dehydration, nutrition-sequelae, assoc with measles, epidemics
- polymicrobial unusual

Developing
- 3-10 episod/y
- any season
- frequent dehydration, common nutrition-sequelae, 15-65% measles assoc, frequent epidemics
- >20% polymicrobial

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4
Q

What are common viruses that cause intestinal disease?

A

Rota
Noro
Astro
Adeno 40/41
Calci
Corona

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5
Q

What are common bacteria that cause intestinal disease?

A

E.coli (EPEC, ETEC, EAggEC, EIEC)
Salmonella
Shigella
Yesenia enterocolitica/pseudotubercolosis
Campylobacter
Vibrio

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6
Q

What are common protozoa that cause intestinal disease?

A

Microsporidia
C. parvum
Isospora belli
Entamoeba histolytica
G. lamblia

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7
Q

What are common trematodes that cause intestinal disease?

A

Fasciolopsis buski
Heterophyes heterophyes
Fasciola hepatica
Clonorchis sinensis

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8
Q

What are common cestodes that cause intestinal disease?

A

Taenia saginata

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9
Q

What are common helminths that cause intestinal disease?

A

Pinworms
Whipworms
Threadworms
Hookworms

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10
Q

Which bacteria causing IID are NOT zoonotic?

A

S. typhi
Shigella

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11
Q

What are the host factors that influence IID?

A

Species, age
Hygiene
Intestinal motility
Specific immunity (phagocytic, humoral, cell-mediated)
Non-specific
Intestinal receptors
Underlying diseases

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12
Q

What are the environmental factors that influence IID?

A

Sanitation
Hygiene
Education
Overcrowding
Climate
Hospitals

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13
Q

What are the microbe factors that influence IID?

A

Transmission mode
Infectious dose
Virulence factors
Toxins

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14
Q

Which bacteria produces mucinase?

A

V. cholera

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15
Q

What are the modes of transmission of IIDs?

A

Predominantly fecal-oral
Person-to-person
Aerosolisation (norovirus after vomiting)

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16
Q

What is the latin name for the common house fly?

A

Musca domestica

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17
Q

How are common house flies related to transmission of IIDs?

A

Transfer focal matter via
- feces on hairy limbs
- stomach contents regurgitation onto food
- defecation onto food

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18
Q

What is it called when a domestic house fly regurgitates its stomach contents?

A

Vomit drop

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19
Q

What are the 3 types of diarrhoea?

A

Acute, chronic, persistent
OR
Non-inflammatory, inflammatory and penetrating

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20
Q

Define acute diarrhoea

A

Loose/watery stools >3x in 24h

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21
Q

Define chronic diarrhoea

A

Diarrhoea lasting >4 weeks

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22
Q

Define persistent diarrhoea

A

Diarrhoea lasting >2 weeks

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23
Q

What is the difference in the epidemic pattern of waterborne vs foodborne diarrhoea?

A

Waterborne - explosive
Foodborne - localised

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24
Q

Discuss the mechanisms of non-inflammatory diarrhoea

A

Adherence and sequelae
- villus tip disruption
- brush border disruption
- enterotoxin production

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25
Name examples of causative organisms of non-inflammatory diarrhoea
ETECT EAEC V. cholerae C. perfringens B. cereus G. lamblia Rotavirus Norovirus C. parvum
26
Discuss the mechanisms of inflammatory diarrhoea
Invasion Cytotoxins
27
Name examples of causative organisms of inflammatory diarrhoea
EIEC S. enteritidis Shigella V. parahemolyticus C. difficile C. jejune Entamoeba histolytica
28
What is significant about penetrating diarrhoea?
Does not primarily present as diarrhoea
29
Name examples of causative organisms of penetrating diarrhoea
S. type Yersinia enterocolitica Campylobacter fetus
30
Name the 5 e.coli types
Enteropathogenic (EPEC) Enterotoxigenic (ETEC) Enteroaggregrative (EAggEC) Enteroinvasive (EIEC) Enterohemorrhagic (EHEC)
31
What is the major cause of infantile diarrhoea (<6m) in developing countries?
EPEC Breastmilk is protective (lipids and immunoglobulins limit adherence)
32
Discuss the features of EPEC
Transmission: person-to-person Reservoir: humans Site: small intestine Treatment: primarily supportive but antibiotics can be used in severe cases to shorten duration Vaccine: none
33
Discuss the pathophysiology of EPEC
Attachment and effacement of enterocytes 1. Intimin (adhesin) allows binding to host intestinal cells 2. Adherence -> actin rearrangement and host cell deformation 3. Moderate invasion of host cells -> inflammation -> loss of microvillus surface area and loosening of tight junctions -> direct fluid secretion
34
Discuss the clinical presentation of EPEC
Severe acute watery diarrhoea Vomiting Fever Can be persistent
35
Discuss the properties of stool in EPEC
Copious Watery RBCs absent WBCs scanty (moderate inflammation)
36
What is the major cause of childhood diarrhoea in developing countries?
ETEC
37
What is the number 1 cause of traveller's diarrhoea?
ETEC
38
Discuss the features of ETEC
Transmission: fecal-oral Reservoir: humans, animals, aquatic sources Site: small intestine Treatment: primarily supportive, anti-motility agents, fluroquinolones Vaccine: no specific, commercially available
39
Discuss the pathophysiology of ETEC
Enterotoxins! 1. Attachment via fimbrial adhesions and colonisation factor antigens 2. No invasion!!! 3. Expression of - heat labile toxin (LT) - heat stable toxin (ST)
40
Discuss the pathophysiology of LT and ST
LT - active adenylate cyclase -> incr cAMP -> incr fluid secretion ST - incr cGMP
41
ETEC's heat labile toxin is similar to which other toxin?
Cholera toxin (similar structure and function)
42
Discuss the clinical presentation of ETEC
Severe acute diarrhoea Abdominal cramping Occasional vomiting
43
Discuss the properties of stool in ETEC
Copious Watery RBCs absent (no invasion) WBCs absent (minimal inflammation)
44
Which e.coli strain is associated with emerging infection in childhood, traveller and persistent diarrhoea?
Enteroaggregative e.coli (EAEC)
45
Discuss the features of EAEC
Transmission: fecal-oral Reservoir: asymptomatic humans Site: small intestine Treatment: primarily supportive, fluoroquinolones for traveller's Vaccine: none
46
Discuss the pathophysiology of EAEC
1. Adherence via bundle-forming pili -> loss of microvillus surface -> decreased absorption 2. Mucus biofilm formation 3. Enterotoxins Plasmid encoded toxin (PET) -> crypt dilation, cell damage, fluid and electrolyte secretion
47
What is the suggested reason for persistence with EAEC?
Mucus biofilm
48
Which enterotoxins are involved in EAEC pathophysiology?
1. Plasmid encoded toxin (PET) -> crypt dilation, cell damage, fluid and electrolyte secretion 2. Enteroaggregative heat stable (EAST) -> fluid and electrolyte secretion
49
Discuss the clinical presentation of EAEC
Severe acute or persistent chronic mucoid diarrhoea Low grade fever
50
Discuss the properties of stool in EAEC
Watery, mucoid Occasional RBCs
51
Which e.coli is the cause of dysenteric-like syndrome?
Enteroinvasive e.coli (EIEC)
52
Discuss the features of EIEC
Transmission: fecal-oral and person-to-person Reservoir: humans Site: LARGE intestine Treatment: primarily supportive Vaccine: none
53
Discuss the pathophysiology of EIEC
1. Attachment -< invasion w/ intracellular motility -> spread -> inflammation and ulceration of colonic wall
54
Discuss the clinical presentation of EIEC
Enterocolitis Fever Cramping Watery -> dysentery Tenesmus
55
Discuss the properties of stool in EIEC
Scant Mucopurulent RBCs common WBCs prominent!
56
What is the most common e.coli serotype?
O157:H7 (EHEC)
57
Which diseases can EHEC cause
Hemorrhagic colitis Hemolytic uremic syndrome
58
Discuss the features of EHEC
Transmission: fecal-oral, person-t-person Reservoir: humans, animals, environment Site: LARGE intestine Treatment: entirely supportive, AVOID antibiotics Vaccine: none
59
In which e.coli species should antibiotics be avoided and why?
EHEC -> induce expression and release of Shiga toxins which is associated with increased HUS in extremes of age
60
Discuss the clinical presentation of EHEC
NO fever! Watery -> dysentery Cramping HUS
61
Discuss the properties of stool in EHEC
Copious Bloody Prominent RBCs Few-absent WBCs
62
What is the primary pathogenic mechanism of ETEC?
Enterotoxin LT/ST
63
What is the primary pathogenic mechanism of EIEC?
Enterocyte invasion
64
What is the primary pathogenic mechanism of EHEC?
Shiga-like cytotoxin
65
What is the primary pathogenic mechanism of EPEC?
Adherence to enterocytes
66
What is the primary site of ETEC?
Small intestine
67
What is the primary site of EIEC?
Large intestine
68
What is the primary site of EHEC?
Large intestine
69
What is the primary site of EPEC?
Small intestine
70
What is the mucosal pathology of ETEC?
Intact hyperaemia
71
What is the mucosal pathology of EIEC?
Necrosis, ulceration and inflammation
72
What is the mucosal pathology of EHEC?
Microvilli destruction Cell death
73
What is the mucosal pathology of EPEC?
Microvilli destruction
74
In which e.coli strains is fever absent and in which stains is fever common?
Absent - ETEC - EHEC Common - EIEC - EPEC
75
When does rotavirus infection peak?
6 and 24m
76
Which family does rotavirus belong to? What kind of virus is it?
Reoviridae dsRNA wheel-shaped virus
77
What is the difference in seasonality of rotavirus in developed vs developing countries?
Developed - winter Developing - year round
78
Discuss the features of rotavirus
Transmission: fecal-oral Reservoirs: humans Treatment: fluids
79
Discuss the clinical presentation of rotavirus
Profuse, watery diarrhoea Low grade fever Vomiting Abdominal cramps
80
How long does rotavirus shed?
8 days
81
How is rotavirus diagnosed?
ELISA Rotastrip (antigen) Electron microscopy
82
Which viruses are non-enveloped and what is important about their IPC?
Rota, adeno, entero Inactivated by alcohol NOT common disinfectants (chlorhexidine, etc)
83
What is the rotavirus vaccine?
Live attenuated vaccine 2 oral doses at 6w and 14w
84
How protective is the rotavirus vaccine?
98% protective
85
Which family does norovirus belong to?
Calciviridae
86
What is the seasonality of norovirus?
Year round transmission Increases in winter in temperate climates
87
Discuss the features of norovirus
Transmission: fecal-oral, person-to-person, aerosolisation Treatment: fluids Vaccine: none
88
Is norovirus highly infectious?
Yes, as few as 18 particles required
89
Discuss the clinical presentation of norovirus
Nausea Projectile vomiting Cramps Low grade fever Myalgia Moderate diarrhoea Lasts 24-72h
90
What is the incubation period of norovirus?
12-48h
91
How long does norovirus shed?
Up to 3w
92
Why is it possible to be infected with norovirus multiple times?
Many genotypes
93
How is norovirus diagnosed?
PCR (stool, vomitus) ELISA (poor sensitivity)
94
How is norovirus prevented?
Hand washing Surface decontamination Food screening (clam/oyster PCR)
95
Which disinfectant inactivates norovirus?
Chlorine NOT alcohol
96
How long can norovirus survive in the environment?
7-12d on surfaces Months in still water
97
How is non-typhoidal salmonella classified?
Genus plus serotype
98
How many species of non-typhoidal salmonella are there?
>1500 antigenically different species
99
Discuss the features of non-typhoidal salmonella
Broad host range (zoonotic) High infectious dose Fecal-oral
100
Discuss the presentation of non-typhoidal salmonella
Fever Vomiting Diarrhoea > enterocolitis Bacteremia
101
What is the pathogenesis of non-typhoidal salmonella infection?
Invasion Inflammation
102
Discuss the treatment of non-typhoidal salmonella
Rehydration Antibiotics for bacteraemia or patient at risk
103
What is the prototype of enteric fever syndrome?
Salmonella typhi
104
Discuss the features of salmonella typhi
Reservoirs: only humans Endemic in SA HIV assoc w/ increased severity 10% excrete bacteria for weeks 4% become carriers (excrete up to 1 year)
105
What is enteric fever syndrome?
Sustained fever that increases over the first week Headache Abdominal pain Diarrhoea -> constipation -> diarrhoea Bacteremia Rash Splenomegaly Bradycardia Cough Arthritis Meningism
106
What is the pathogenesis of salmonella typhi?
1. Faecal-oral ingestion with 15d incubation 2. Gut mucosa penetration -> uptake by macrophages -> carried via lymphatics to mesenteric lymph nodes -> blood stream via thoracic duct -> RES and other organs -> biliary infection reseeds the intestine
107
What causes the inflammatory response in salmonella typhi?
LPS endotoxin
108
Name complications of salmonella typhi
Abdo - GIT haemorrhage > perforation - Cholecystitis Lung - Pneumonia - Empyema CVS - Thrombophlebitis - Pericarditis - Myocarditis - Sepsis CNS - Meningitis - Polyneuritis - Toxic psychosis
109
When will blood and bone marrow be positive for salmonella typhi?
Week 1
110
When will stool be positive for salmonella typhi?
Week 3
111
When will urine be positive for salmonella typhi?
Week 3-4 Transient 25% of patients
112
What are FBC findings in salmonella typhi?
Decreased WCC with lymphocytosis
113
Discuss the treatment of salmonella typhi
IV fluids Fluoroquinolones Ceftriaxone Azithromycin
114
Which patient populations often experience relapsing salmonella typhi infection?
Carriers HIV Schistosomiasis
115
Discuss prevention of salmonella typhi
Hygiene Vaccine (Ty21a Vi polysaccharide)
116
Name 4 species of shigella
S. flexneri S. sonnei S. boydi S. dysenteriae
117
Discuss the features of shigella
Transmission: fecal-oral, person-to-person Reservoir: humans Low infectious dose
118
Discuss the pathogenesis of shigella
Invasion Verocytotoxin (shiga toxin)
119
Discuss the clinical presentation of shigella
Dysentery HUS Systemic (immunocompromised)
120
Discuss the treatment of shigella
Fluids Antibiotics (CTX, fluoroquinolone) AVOID anti-motility!!!
121
Name bacterial causes of dysenteric syndrome
Shigella Campylobacter EIEC
122
What is dysenteric syndrome?
An inflammatory, invasive, hemorrhagic process involving the colon and occasionally distal small intestine
123
Discuss the clinical presentation of dysenteric syndrome
Fever Vomiting Diarrhoea Tenesmus
124
Name parasitic causes of dysenteric syndrome
Entamoeba histolytica
125
How many stages does entamoeba histolytica have?
2 - trophozoite and cyst
126
How does vibrio cholera appear on microscopy?
Gram negative Comma shaped Single polar flagella
127
What is the nomenclature for classifying vibrio cholera?
Genus, species, serogroup, biotype, serotype Eg vibrio cholerae O1 El Tor
128
What are the 2 main biotypes of v. cholera?
O1 classical and El Tor
129
What are the 2 main serotypes of v.cholerae?
Ogawa Inaba
130
What is the host of v.cholerae?
Humans are the ONLY host
131
Discuss the features of v.cholerae
Faecal-oral transmission (person-to-person rare) High infectious dose
132
Which strains are the main cause of epidemic cholera?
Toxigenic strains
133
Which biotype has more asymptomatic infections than the other?
El Tor
134
What are the interepidemic reservoirs of v.cholerae?
Copepods Plankton Crustaceans
135
Which cholera pandemic are we in now?
7th great pandemic
136
What is the theory regarding the re-emergence of El Tor biotype?
Global warming with El Niño -> warmer seawater -> phytoplankton expansion -> zooplankton copepods which carry v.cholerae on the surface and gut -> widespread dissemination
137
Discuss the virulence factors of v.cholerae
Motility Adherence Enterotoxin (cholera toxin)
138
Discuss the pathogenesis of cholera toxin
1. B subunits attach to GMI ganglioside receptors 2. A subunits enter intestinal epithelial cells -> activate adenylate cyclase -> increased cAMP which acts on small intestine epithelial cells w/ direct secretory effect on crypt cells and anti-absorption effect on villus cells
139
Discuss the clinical presentation of cholera
No fever Vomiting Rice water diarrhoea
140
Discuss the management of cholera
Rehydration Antimicrobials to decrease diarrhoea Monitor urine and stool output Mass prophylaxis discourage Vaccines
141
What is the 'bengal' v.cholerae biotype?
O139
142
How does campylobacter appear on microscopy?
Gram negative spiral "Seagull wing"
143
Which campylobacter spp cause human infection?
>10 spp Most common: jejuni, coli
144
Discuss the features of c.jejuni infection
Inflammatory diarrhoea (invasion, cytotoxin) Distal small intestine and colonic dysentery
145
What is the treatment of c.jejuni?
Azithromycin
146
Name complications of c.jejuni
Guillain Barre Syndrome HUS
147
Discuss the features of campylobacter fetus
Cattle/sheep abortion Cause thrombophlebitis and bacteria in humans with dissemination to other organs
148
What is the treatment of choice for campylobacter foetus?
Gentamicin Ceftriaxone (CNS)
149
Which bacteria cause traveller's diarrhoea?
ETEC EAEC Shigella Salmonella Campylobacter Cholera
150
Which viruses cause traveller's diarrhoea?
Rotavirus Calcivirus Astrovirus SRS (small round structured) Hepatitis A
151
Which protozoa cause traveller's diarrhoea?
G. lamblia Crypto parvum
152
Which bacteria cause infantile diarrhoea?
Diarrhoeagenic e.coli Shigella Salmonella Yersinia enterocolitica
153
Which protozoa cause infantile diarrhoea?
G. lamblia
154
Which viruses cause infantile diarrhoea?
Rotavirus Adenovirus (41, 42, 44) Echovirus
155
Which pathogens commonly cause weaning diarrhoea in developing vs developed countries?
Developing - bacterial Developed - rotavirus
156
Discuss the new strain of c.difficile
B1/NAP1/O27 Produces more toxins Increased fluoroquinolone resistance Also community acquired
157
What is the pathogenesis of c.diff?
1. Disruption of colonic membrane -> colonisation 2. Toxin A/B release 3. Mucosal injury and inflammation
158
What are the two toxins released by c.diff?
A - enterotoxin B - cytotoxin
159
What are complications of acute infectious diarrhoea illness?
Chronic diarrhoea IBS Reiter's syndrome HUS
160
Which organisms are most likely to cause Reiter's syndrome?
Shigella Salmonella Campylobacter
161

DTMH Block 3 (18 decks)

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