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Diarrhoea Flashcards

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1
Q

What is the epidemiology and global burden of diarrhoeal illness?

A

1.3 million deaths per year
Leading cause of infectious death globally
Sub saharan africa > SEA > South America

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2
Q

What is the GEMS trial?

A

Global Enteric Multicentre Study, which provided ground breaking information about the most common causes of childhood diarrhoeal illness

It also found out that shigella does not always cause dysentery, and absence of dysentery does not rule out shigella

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3
Q

What 4 causes of diarrhoea cause the most deaths globally?

A

Rotavirus
Shigella
Salmonella
Cryptosporidium

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4
Q

What are the 6 main causes of diarrhoeal illness in children as per the GEMS trial?

A

Rotavirus
Shigella
ST-ETEC (enterotoxic e coli)
Cryptosporidium
adenovirus
Campylobacter

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5
Q

What is the global burden of cholera?

A

1.3 billion people at risk

95 000 deaths per year

Occurs in epidemics

**Be concerned re: cholera if you have adults dying of diarrhoeal illness

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6
Q

What is the global burden of shigella?

A

Accounts for 50% of all dysentery
One of the top 5 causes of diarrhoeal illness in children

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7
Q

What is microbiology of shigella?

A

Gram negative straight bacillus
Aerobic

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8
Q

What are the 4 common types of shiga bacteria?

A

Sonnei
flexneri
Boydi
dysenteriae

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9
Q

Which shigella spp. is most common in HICs?

A

Shigella Sonnei

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10
Q

Which shigella spp. is most common in LMICs?

A

Shigella flexneri

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11
Q

Which shigella spp. is assocaited with outbreaks during conflict/displacment?

A

Shigella dysenteriae

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12
Q

Who is at high risk of shigella infection?

A

Children
MSM
Travellers
Poverty
Overcrowding
Areas of poor water sanitation

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13
Q

Is shigella resistant to gastric acid?

A

YES

This is important because it means that you don’t need to come into contact with very much of the bacteria to get sick…

Also helps to account for the fact that shigella can cause epidemics

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14
Q

What is the incubation of shigella?

A

1-8 days

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15
Q

What is the presentation of shigella?

A

High fever
Watery ± bloody diarrhoea
Malaise
Abdo Pain
Vomiting

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16
Q

What are the complications of shigella infection?

A
  1. Death
  2. Rectal prolapse
  3. Toxic megacolon ± intestinal perforation
  4. Dehydration
  5. Hyponatraemia and hypoglycaemia
  6. Leukaemiod reaction
  7. HUS
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17
Q

What is the diagnosis of shigella?

A

PCR
Culture
Rectal Swabs

**Note that serology is NOT helpful

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18
Q

What is the treatment of shigella?

A

ORS / IV fluids if not tolerating oral intake
Zinc supplements
Ciprofloxacin for 3/7 at least
- ADULTS: 500mg BD for 3/7
- CHILDREN: 15mg/kg BD for 3/7

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19
Q

What second line antibiotics can be used in shigellosis?

A

Ceftriaxone
Azithromycin

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20
Q

What is antibiotic resistance common in shigellosis?

A

Significant S. Sonnei resistance in Europe

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21
Q

What are the side effects of ciprofloxacin

A

Arthropathy
Tendonitis and tendon rupture

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22
Q

How can shigella be prevented?

A

Improved sanitation –> highly sensitive to chlorine!!!

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23
Q

What is the WHO definitiion of cholera?

A

(a) in area where cholera not known to be present, patient ≥ 5 years develops severe dehydration or dies from acute watery diarrhoea;
(b) Area in which there is a cholera outbreak, any patient ≥ 5 years who develops acute watery diarrhoea with or without vomiting

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24
Q

How many global cholera pandemics have there been?

A

7; all seem to have stemmed from bangladesh area

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25
What is the bacteriology of cholera?
Vibrio cholera Gram negative curved bacilli Multiple serogroups
26
What are the serotypes of vibrio cholerae?
Serogroup O1 - Classical - El Tor Serogroup O139
27
What is the infectious dose of vibrio cholerae?
10000-100000 organisms
28
What is the pathophysiology of cholera?
Cholera passes through the stomach (sensitive to gastric acid, which is why you need to be infected by so many organisms to get an infection) The bacteria that make it through the intestine colonise the small bowel, where they attach to the bowel mucosa. They contain 2 binding sites, which produce toxic response Toxin: 2 subunits B= binding A= active A enters cell -> stimulates cAMP -> NaCl absorption inhibited, Cl excretion stimulated -> net loss of water, NaCl, K, bicarbonate
29
What are the symptoms of cholera?
1. ASYMPTOMATIC (75%) 2. Mild - Moderate Illness Rice water stools +/- bloating +/- vomiting Ileus Muscle weakness/cramps 3. Severe requiring hospitalisation (2%) Severe dehydration
30
What are the complications of cholera infection?
Hypoglycaemia (especially in children) Arrythmias ARF Shock Coma Death Mortality 5-10%
31
What is the mortality of cholera?
5-10%
32
Where is the majority burden of cholera globally
Sub- saharan Africa (primarily east africa) South East Asia
33
What are the reservoirs/hosts of cholera?
Humans Shellfish
34
Which cholera strain is most associated with pandemics?
O1 El Tor
35
Which diarrhoeal illnesses are sensitive to chlorine?
Shigella Cholera
36
Which diarrhoeal illnesses are not sensitive to chlorine?
E. Histolytica Giardia Cryptosporidia
37
How is cholera diagnosed?
1. Clinical diagnosis based on WHO definition 2. Stool culture 3. VC RDT 4. Dark Field Microscopy
38
How do you manage Cholera?
IV Fluids ±IV Abx ±ORS +Zinc in children
39
What IV fluids should you give to children with severe shock secondary to cholera + fluid losses?
<1 year: 30ml/kg over 60min + 70ml/kg over 5 hours >1 year: 30ml/kg over 30 min + 70ml/kg over 2.5 hours
40
How does ORS improve dehydration?
Changes lumenal osmolality levels, which adjusts fluid shifts Shortens duration of diarrhoea Reduces stool volume Reduces need for unscheduled iv fluids
41
How can you quickly make your own ORS solution if none is available?
One level teaspoon of salt + eight level teaspoons of sugar + one litre of clean water
42
What antibiotic can be used in cholera?
Azithromycin in epidemics otherwise: Doxycycline (adults only, ideally): 4mg/kg stat OR Erythromycin OR Ciprofloxacin
43
During an epidemic, what is the expected 'attack rate' of cholera? Of these, what percentage are likely to require parenteral intervention?
5% 75% are likely to need IVF in epidemic cholera
44
How can cholera be prevented?
Early case detection Water chlorination Improve hygiene practices Vaccination (in outbreaks only) Safe corpse disposal
45
Is there a cholera vaccine?
Yes, multiple Dukoral --> oral cholera vaccine Used in epidemics/outbreaks only Licensed to be used in people >1 years old. Two doses 14 days apart required
46
Bacteriologically, shigella are...?
Gram negative straight rods
47
Which strain of shigella has been absent since the 1990s?
Shigella boydii
48
What effect does cholera toxin have on Chloride?
Prevents the re-absorption of chloride at via CFTR channels Inhibits sodium chloride absorption resulting in an efflux of chloride ions and secretion of hydrogencarbonate ions, sodium and potassium ions, and water. Loss of chloride prompts substantial fluid secretion into the small intestine, overwhelming the resorptive capacity of the large intestine, resulting in severe watery diarrhoea.
49
What is Typhoid Fever?
'Enteric Fever' A bacterial diarrhoeal illness with rapidly growing worldwide AMR
50
What is the epidemiology of TF?
GLOBAL BURDEN: 14 million cases a year Highest incidence in ASIA: Bangladesh, India, Pakistan but occurs in Africa, South + Central america too Commonest cause of bacterial fever in the returning traveller Children > Adults
51
What are the causative organisms of TF?
Salmonella Typhi Salmonella paratyphi A + B
52
What is the bacteriology of Typhoid Fever?
Salmonella Typhi Salmonella paratyphi A + B ARE: Gram negative obligate intracellular organism (i.e. it hangs out in the macrophages)
53
How is TF spread?
Faecal-oral spread
54
What are the risk factors for severe typhoidal infection?
PPI Use Infection with AMR strain
55
What is the pathophysiology of Typhoid Fever?
Patient ingests Typhoid (need to consume at least 100 000 bacteria for infection to occur)  passes through the stomach  Goes into the small intestine at the PEYER’S PATCHES where it is taken up by macrophages where it goes to the mesenteric lymph nodes  Spleen and Liver via blood  Gall bladder enters into the small bowel  colonises the S.I where the PEYER’S PATCHES Symptoms occur when S. Typhi is in the blood stream
56
In chronic carriers of S. Typhi / S paratyphi, where is the organism likely to sequester?
Gall bladder and biliary tree
57
What are the symptoms of TF?
Acute Fever, slowly rising over a few days Faget's sign Headache, malaise Hepatosplenomegaly , abdo distension, mild ascites Rose Spots
58
What three infectious diseases are known to cause Faget's sign?
Typhoid Fever Yellow Fever Brucellosis
59
What is the DDx for Typhoid Fever?
**You must rule out Malaria and Dengue** Leptospirosis Brucellosis Schistosomiasis Viral GE
60
How do you diagnose Typhoid Fever?
Blood Culture is the gold standard (negative result does not rule out TF) - Two sets of paired samples are recommended as it is notoriously hard to get a good lab result Bone Marrow biopsy (bit brutal) Widal test (serology) is no longer recommended -- not sensitive or specific VI Serology can be used in non-endemic settings (e.g. UK) to cool for chronic carriage of Salmonella Typhi Bloods: Mild transamintis RDTs: lots exist, but arent great; none test for S. Paratyphoid
61
How do you manage Typhoid Fever?
**** Lots of AMR globally, especially in South Asia Ciprofloxacin 20mg/kg for 7/7 ± Doxycycline If AMR: Azithromycin 20mg/kg for 77 +/- Steroids if concerns about severe disease
62
What are the complications of Typhoid Fever
Complications start to occur >10 after illness starts Typhoid Encephalopathy (up to 12%) Nephritis Hepatitis UGIB GI Perf Dead (CFR 2.5%)§
63
How do you prevent Typhoid Fever?
WASH techniques Typhoid Vacccine (TCV Vax, safe to use in children >6 months old)
64
Which country is assocaited with highest number of cases of Multidrug resistant Typhoid Fever?
Pakistan
65
What is the prognosis of Typhoid Fever?
Prolonged febrile illness with bacteraemia 90% uncomplicated 10% severe complicated disease 10% + mortality with no treatment < 1% mortality if adequate treatment
66
Which parasitic co-infection is associated with chronic carriage of Typhoid?
Shistosomiasis (unknown why)
67
How is Typhoid Fever usually transmitted?
Typhoid is usually acquired through ingestion of food or water contaminated by faeces of a patient or carrier
68
What is the incubation of typhoid?
10-20 days
69
How do you manage fluid loss in Diarrhoeal Illness?
70
What are the differences between Typhoid and Invasive Non-typhoidal Salmonella?
Typhoid - Salmonella Typhi and S. Paratyphi - invasive (always) - mortality up to 20% - humans are the only host iNTS - S. Typhimurium and S. Enteritidis - HIV (200x more likely if HIV+ve) -Case fatality rate up to 20% - multiple hosts, not just humans (usually spread from animal contact)
71
What two bacteria are responsible for iNTS?
Salmonella Enteritidis Salmonella Typhimurium
72
How does iNTS present?
** have a suspicion in any HIV patient with fever, hepatosplenomegaly, diarrhoea and cough Very non-specific and could be the very bottom of your list if differentials so keep an eye out for it
73
What are the complications of iNTS?
1. Recurrence (higher risk of mortality with each subsequent recurrence) 2. Death 3. Concurrent infections

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