Intestinal diseases Flashcards
What is the leading cause of morbidity and mortality worldwide?
Gastroenteritis
Where are infectious intestinal diseases usually contracted in the UK?
Home
Compare paediatric diarrhoea in developed vs developing countries
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
What are common viruses that cause intestinal disease?
Rota
Noro
Astro
Adeno 40/41
Calci
Corona
What are common bacteria that cause intestinal disease?
E.coli (EPEC, ETEC, EAggEC, EIEC)
Salmonella
Shigella
Yesenia enterocolitica/pseudotubercolosis
Campylobacter
Vibrio
What are common protozoa that cause intestinal disease?
Microsporidia
C. parvum
Isospora belli
Entamoeba histolytica
G. lamblia
What are common trematodes that cause intestinal disease?
Fasciolopsis buski
Heterophyes heterophyes
Fasciola hepatica
Clonorchis sinensis
What are common cestodes that cause intestinal disease?
Taenia saginata
What are common helminths that cause intestinal disease?
Pinworms
Whipworms
Threadworms
Hookworms
Which bacteria causing IID are NOT zoonotic?
S. typhi
Shigella
What are the host factors that influence IID?
Species, age
Hygiene
Intestinal motility
Specific immunity (phagocytic, humoral, cell-mediated)
Non-specific
Intestinal receptors
Underlying diseases
What are the environmental factors that influence IID?
Sanitation
Hygiene
Education
Overcrowding
Climate
Hospitals
What are the microbe factors that influence IID?
Transmission mode
Infectious dose
Virulence factors
Toxins
Which bacteria produces mucinase?
V. cholera
What are the modes of transmission of IIDs?
Predominantly fecal-oral
Person-to-person
Aerosolisation (norovirus after vomiting)
What is the latin name for the common house fly?
Musca domestica
How are common house flies related to transmission of IIDs?
Transfer focal matter via
- feces on hairy limbs
- stomach contents regurgitation onto food
- defecation onto food
What is it called when a domestic house fly regurgitates its stomach contents?
Vomit drop
What are the 3 types of diarrhoea?
Acute, chronic, persistent
OR
Non-inflammatory, inflammatory and penetrating
Define acute diarrhoea
Loose/watery stools >3x in 24h
Define chronic diarrhoea
Diarrhoea lasting >4 weeks
Define persistent diarrhoea
Diarrhoea lasting >2 weeks
What is the difference in the epidemic pattern of waterborne vs foodborne diarrhoea?
Waterborne - explosive
Foodborne - localised
Discuss the mechanisms of non-inflammatory diarrhoea
Adherence and sequelae
- villus tip disruption
- brush border disruption
- enterotoxin production
Name examples of causative organisms of non-inflammatory diarrhoea
ETECT
EAEC
V. cholerae
C. perfringens
B. cereus
G. lamblia
Rotavirus
Norovirus
C. parvum
Discuss the mechanisms of inflammatory diarrhoea
Invasion
Cytotoxins
Name examples of causative organisms of inflammatory diarrhoea
EIEC
S. enteritidis
Shigella
V. parahemolyticus
C. difficile
C. jejune
Entamoeba histolytica
What is significant about penetrating diarrhoea?
Does not primarily present as diarrhoea
Name examples of causative organisms of penetrating diarrhoea
S. type
Yersinia enterocolitica
Campylobacter fetus
Name the 5 e.coli types
Enteropathogenic (EPEC)
Enterotoxigenic (ETEC)
Enteroaggregrative (EAggEC)
Enteroinvasive (EIEC)
Enterohemorrhagic (EHEC)
What is the major cause of infantile diarrhoea (<6m) in developing countries?
EPEC
Breastmilk is protective (lipids and immunoglobulins limit adherence)
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
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
Discuss the clinical presentation of EPEC
Severe acute watery diarrhoea
Vomiting
Fever
Can be persistent
Discuss the properties of stool in EPEC
Copious
Watery
RBCs absent
WBCs scanty (moderate inflammation)
What is the major cause of childhood diarrhoea in developing countries?
ETEC
What is the number 1 cause of traveller’s diarrhoea?
ETEC
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
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)
Discuss the pathophysiology of LT and ST
LT
- active adenylate cyclase -> incr cAMP -> incr fluid secretion
ST
- incr cGMP
ETEC’s heat labile toxin is similar to which other toxin?
Cholera toxin (similar structure and function)
Discuss the clinical presentation of ETEC
Severe acute diarrhoea
Abdominal cramping
Occasional vomiting
Discuss the properties of stool in ETEC
Copious
Watery
RBCs absent (no invasion)
WBCs absent (minimal inflammation)
Which e.coli strain is associated with emerging infection in childhood, traveller and persistent diarrhoea?
Enteroaggregative e.coli (EAEC)
Discuss the features of EAEC
Transmission: fecal-oral
Reservoir: asymptomatic humans
Site: small intestine
Treatment: primarily supportive, fluoroquinolones for traveller’s
Vaccine: none
Discuss the pathophysiology of EAEC
- Adherence via bundle-forming pili -> loss of microvillus surface -> decreased absorption
- Mucus biofilm formation
- Enterotoxins
Plasmid encoded toxin (PET) -> crypt dilation, cell damage, fluid and electrolyte secretion
What is the suggested reason for persistence with EAEC?
Mucus biofilm
Which enterotoxins are involved in EAEC pathophysiology?
- Plasmid encoded toxin (PET) -> crypt dilation, cell damage, fluid and electrolyte secretion
- Enteroaggregative heat stable (EAST) -> fluid and electrolyte secretion
Discuss the clinical presentation of EAEC
Severe acute or persistent chronic mucoid diarrhoea
Low grade fever
Discuss the properties of stool in EAEC
Watery, mucoid
Occasional RBCs
Which e.coli is the cause of dysenteric-like syndrome?
Enteroinvasive e.coli (EIEC)
Discuss the features of EIEC
Transmission: fecal-oral and person-to-person
Reservoir: humans
Site: LARGE intestine
Treatment: primarily supportive
Vaccine: none
Discuss the pathophysiology of EIEC
- Attachment -< invasion w/ intracellular motility -> spread -> inflammation and ulceration of colonic wall
Discuss the clinical presentation of EIEC
Enterocolitis
Fever
Cramping
Watery -> dysentery
Tenesmus
Discuss the properties of stool in EIEC
Scant
Mucopurulent
RBCs common
WBCs prominent!
What is the most common e.coli serotype?
O157:H7 (EHEC)
Which diseases can EHEC cause
Hemorrhagic colitis
Hemolytic uremic syndrome
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
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
Discuss the clinical presentation of EHEC
NO fever!
Watery -> dysentery
Cramping
HUS
Discuss the properties of stool in EHEC
Copious
Bloody
Prominent RBCs
Few-absent WBCs
What is the primary pathogenic mechanism of ETEC?
Enterotoxin LT/ST
What is the primary pathogenic mechanism of EIEC?
Enterocyte invasion
What is the primary pathogenic mechanism of EHEC?
Shiga-like cytotoxin
What is the primary pathogenic mechanism of EPEC?
Adherence to enterocytes
What is the primary site of ETEC?
Small intestine
What is the primary site of EIEC?
Large intestine
What is the primary site of EHEC?
Large intestine
What is the primary site of EPEC?
Small intestine
What is the mucosal pathology of ETEC?
Intact hyperaemia
What is the mucosal pathology of EIEC?
Necrosis, ulceration and inflammation
What is the mucosal pathology of EHEC?
Microvilli destruction
Cell death
What is the mucosal pathology of EPEC?
Microvilli destruction
In which e.coli strains is fever absent and in which stains is fever common?
Absent
- ETEC
- EHEC
Common
- EIEC
- EPEC
When does rotavirus infection peak?
6 and 24m
Which family does rotavirus belong to? What kind of virus is it?
Reoviridae
dsRNA wheel-shaped virus
What is the difference in seasonality of rotavirus in developed vs developing countries?
Developed - winter
Developing - year round
Discuss the features of rotavirus
Transmission: fecal-oral
Reservoirs: humans
Treatment: fluids
Discuss the clinical presentation of rotavirus
Profuse, watery diarrhoea
Low grade fever
Vomiting
Abdominal cramps
How long does rotavirus shed?
8 days
How is rotavirus diagnosed?
ELISA
Rotastrip (antigen)
Electron microscopy
Which viruses are non-enveloped and what is important about their IPC?
Rota, adeno, entero
Inactivated by alcohol NOT common disinfectants (chlorhexidine, etc)
What is the rotavirus vaccine?
Live attenuated vaccine
2 oral doses at 6w and 14w
How protective is the rotavirus vaccine?
98% protective
Which family does norovirus belong to?
Calciviridae
What is the seasonality of norovirus?
Year round transmission
Increases in winter in temperate climates
Discuss the features of norovirus
Transmission: fecal-oral, person-to-person, aerosolisation
Treatment: fluids
Vaccine: none
Is norovirus highly infectious?
Yes, as few as 18 particles required
Discuss the clinical presentation of norovirus
Nausea
Projectile vomiting
Cramps
Low grade fever
Myalgia
Moderate diarrhoea
Lasts 24-72h
What is the incubation period of norovirus?
12-48h
How long does norovirus shed?
Up to 3w
Why is it possible to be infected with norovirus multiple times?
Many genotypes
How is norovirus diagnosed?
PCR (stool, vomitus)
ELISA (poor sensitivity)
How is norovirus prevented?
Hand washing
Surface decontamination
Food screening (clam/oyster PCR)
Which disinfectant inactivates norovirus?
Chlorine NOT alcohol
How long can norovirus survive in the environment?
7-12d on surfaces
Months in still water
How is non-typhoidal salmonella classified?
Genus plus serotype
How many species of non-typhoidal salmonella are there?
> 1500 antigenically different species
Discuss the features of non-typhoidal salmonella
Broad host range (zoonotic)
High infectious dose
Fecal-oral
Discuss the presentation of non-typhoidal salmonella
Fever
Vomiting
Diarrhoea > enterocolitis
Bacteremia
What is the pathogenesis of non-typhoidal salmonella infection?
Invasion
Inflammation
Discuss the treatment of non-typhoidal salmonella
Rehydration
Antibiotics for bacteraemia or patient at risk
What is the prototype of enteric fever syndrome?
Salmonella typhi
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)
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
What is the pathogenesis of salmonella typhi?
- Faecal-oral ingestion with 15d incubation
- 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
What causes the inflammatory response in salmonella typhi?
LPS endotoxin
Name complications of salmonella typhi
Abdo
- GIT haemorrhage > perforation
- Cholecystitis
Lung
- Pneumonia
- Empyema
CVS
- Thrombophlebitis
- Pericarditis
- Myocarditis
- Sepsis
CNS
- Meningitis
- Polyneuritis
- Toxic psychosis
When will blood and bone marrow be positive for salmonella typhi?
Week 1
When will stool be positive for salmonella typhi?
Week 3
When will urine be positive for salmonella typhi?
Week 3-4
Transient
25% of patients
What are FBC findings in salmonella typhi?
Decreased WCC with lymphocytosis
Discuss the treatment of salmonella typhi
IV fluids
Fluoroquinolones
Ceftriaxone
Azithromycin
Which patient populations often experience relapsing salmonella typhi infection?
Carriers
HIV
Schistosomiasis
Discuss prevention of salmonella typhi
Hygiene
Vaccine (Ty21a Vi polysaccharide)
Name 4 species of shigella
S. flexneri
S. sonnei
S. boydi
S. dysenteriae
Discuss the features of shigella
Transmission: fecal-oral, person-to-person
Reservoir: humans
Low infectious dose
Discuss the pathogenesis of shigella
Invasion
Verocytotoxin (shiga toxin)
Discuss the clinical presentation of shigella
Dysentery
HUS
Systemic (immunocompromised)
Discuss the treatment of shigella
Fluids
Antibiotics (CTX, fluoroquinolone)
AVOID anti-motility!!!
Name bacterial causes of dysenteric syndrome
Shigella
Campylobacter
EIEC
What is dysenteric syndrome?
An inflammatory, invasive, hemorrhagic process involving the colon and occasionally distal small intestine
Discuss the clinical presentation of dysenteric syndrome
Fever
Vomiting
Diarrhoea
Tenesmus
Name parasitic causes of dysenteric syndrome
Entamoeba histolytica
How many stages does entamoeba histolytica have?
2 - trophozoite and cyst
How does vibrio cholera appear on microscopy?
Gram negative
Comma shaped
Single polar flagella
What is the nomenclature for classifying vibrio cholera?
Genus, species, serogroup, biotype, serotype
Eg vibrio cholerae O1 El Tor
What are the 2 main biotypes of v. cholera?
O1 classical and El Tor
What are the 2 main serotypes of v.cholerae?
Ogawa
Inaba
What is the host of v.cholerae?
Humans are the ONLY host
Discuss the features of v.cholerae
Faecal-oral transmission (person-to-person rare)
High infectious dose
Which strains are the main cause of epidemic cholera?
Toxigenic strains
Which biotype has more asymptomatic infections than the other?
El Tor
What are the interepidemic reservoirs of v.cholerae?
Copepods
Plankton
Crustaceans
Which cholera pandemic are we in now?
7th great pandemic
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
Discuss the virulence factors of v.cholerae
Motility
Adherence
Enterotoxin (cholera toxin)
Discuss the pathogenesis of cholera toxin
- B subunits attach to GMI ganglioside receptors
- 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
Discuss the clinical presentation of cholera
No fever
Vomiting
Rice water diarrhoea
Discuss the management of cholera
Rehydration
Antimicrobials to decrease diarrhoea
Monitor urine and stool output
Mass prophylaxis discourage
Vaccines
What is the ‘bengal’ v.cholerae biotype?
O139
How does campylobacter appear on microscopy?
Gram negative spiral
“Seagull wing”
Which campylobacter spp cause human infection?
> 10 spp
Most common: jejuni, coli
Discuss the features of c.jejuni infection
Inflammatory diarrhoea (invasion, cytotoxin)
Distal small intestine and colonic dysentery
What is the treatment of c.jejuni?
Azithromycin
Name complications of c.jejuni
Guillain Barre Syndrome
HUS
Discuss the features of campylobacter fetus
Cattle/sheep abortion
Cause thrombophlebitis and bacteria in humans with dissemination to other organs
What is the treatment of choice for campylobacter foetus?
Gentamicin
Ceftriaxone (CNS)
Which bacteria cause traveller’s diarrhoea?
ETEC
EAEC
Shigella
Salmonella
Campylobacter
Cholera
Which viruses cause traveller’s diarrhoea?
Rotavirus
Calcivirus
Astrovirus
SRS (small round structured)
Hepatitis A
Which protozoa cause traveller’s diarrhoea?
G. lamblia
Crypto parvum
Which bacteria cause infantile diarrhoea?
Diarrhoeagenic e.coli
Shigella
Salmonella
Yersinia enterocolitica
Which protozoa cause infantile diarrhoea?
G. lamblia
Which viruses cause infantile diarrhoea?
Rotavirus
Adenovirus (41, 42, 44)
Echovirus
Which pathogens commonly cause weaning diarrhoea in developing vs developed countries?
Developing - bacterial
Developed - rotavirus
Discuss the new strain of c.difficile
B1/NAP1/O27
Produces more toxins
Increased fluoroquinolone resistance
Also community acquired
What is the pathogenesis of c.diff?
- Disruption of colonic membrane -> colonisation
- Toxin A/B release
- Mucosal injury and inflammation
What are the two toxins released by c.diff?
A - enterotoxin
B - cytotoxin
What are complications of acute infectious diarrhoea illness?
Chronic diarrhoea
IBS
Reiter’s syndrome
HUS
Which organisms are most likely to cause Reiter’s syndrome?
Shigella
Salmonella
Campylobacter