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Nagasaki Flashcard Extravaganza > Diarrhoeal diseases > Flashcards

Diarrhoeal diseases Flashcards

1
Q

What is the definition of diarrhoea?

A

Passage of ≥3 loose or watery bowel motions in 24 h
1. Acute watery
diarrhoea without
blood (enteritis)
2. Acute bloody
diarrhoea
(dysentery)
3. Persistent (chronic) : > 14 days

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2
Q

What are the types of shigella?

A

4 ->
S. Dysenteriae causes epidemics
S. Flexneri causes endemic dysentery in developing countries
S Boydii is common in the Indian subcontinent
S Sonneii is a common cause in the industrialised world

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3
Q

What are the top six causative organisms of childhood diarrhoea?

A
  • Shigella
  • Rotavirus
  • Adenovirus
  • ST-ETEC
  • Cryptosporidium
  • Campylobacter
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4
Q

What are the clinical features and complications of shigella?

A

Bloody diarrhoea +/- mucus after 1-7 days
“Redcurrant jelly” stool
Children may have meningoencephalitis
Complications: fulminant colitis or toxic megacolon, perforation, HUS, sepsis

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5
Q

How to test for shigella?

A

PCR/culture

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6
Q

Who gets zinc in diarrhoea illness and how long?

A

Children <5 years – oral zinc 10/7 course

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7
Q
A
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8
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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9
Q

What 4 causes of diarrhoea cause the most deaths globally?

A

Rotavirus
Shigella
Salmonella
Cryptosporidium

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10
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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11
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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12
Q

What is microbiology of shigella?

A

Gram negative straight bacillus
Aerobic

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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 diagnosis of shigella?

A

PCR
Culture
Rectal Swabs

**Note that serology is NOT helpful

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16
Q

What is the treatment of shigella?

A

ORS / IV fluids if not tolerating oral intake
Zinc supplements if <5
Ciprofloxacin for 3/7 at least
- ADULTS: 500mg BD for 3/7
- CHILDREN: 15mg/kg BD for 3/7
High levels of resistance esp high income countries - may require carbapenems

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17
Q

What is the WHO definition 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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18
Q

What is the bacteriology of cholera?

A

Vibrio cholera
Gram negative curved bacilli
Multiple serogroups
Golden yellow colonies on selective media

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19
Q

What are the serotypes of vibrio cholerae?

A

Serogroup O1
- Classical
- El Tor

Serogroup O139

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20
Q

What is the infectious dose of vibrio cholerae?

A

10000-100000 organisms

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21
Q

What is the pathophysiology of cholera?

A

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

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22
Q

What are the symptoms of cholera?

A
  1. ASYMPTOMATIC (75%)
    - human only natural host
  2. Mild - Moderate Illness
    Rice water stools
    +/- bloating
    +/- vomiting
    Ileus
    Muscle weakness/cramps
  3. Severe requiring hospitalisation (2%)
    Severe dehydration
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23
Q

What is the mortality of cholera?

A

5-10%

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24
Q

What are the reservoirs/hosts of cholera?

A

Humans
Shellfish

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25
Q

Which cholera strain is most associated with pandemics?

A

O1 El Tor

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26
Q

How is cholera diagnosed?

A
  1. Clinical diagnosis based on WHO definition
  2. Stool culture
  3. VC RDT
  4. Dark Field Microscopy
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27
Q

What antibiotic can be used in cholera?

A

Azithromycin in epidemics

otherwise:
Doxycycline (adults only, ideally): 4mg/kg stat

OR
Erythromycin

OR
Ciprofloxacin

28
Q

How is cholera managed?

A

Fluids +/- abx

29
Q

During an epidemic, what is the expected ‘attack rate’ of cholera?

Of these, what percentage are likely to require parenteral intervention?

A

5%

75% are likely to need IVF in epidemic cholera

30
Q

How can cholera be prevented?

A

Early case detection
Water chlorination
Improve hygiene practices
Vaccination (in outbreaks only)
Safe corpse disposal

31
Q

Is there a cholera vaccine?

A

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

32
Q

What effect does cholera toxin have on Chloride?

A

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.

33
Q

What is Typhoid Fever?

A

‘Enteric Fever’

A bacterial diarrhoeal illness with rapidly growing worldwide AMR

34
Q

What is the epidemiology of TF?

A

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

35
Q

What are the causative organisms of TF?

A

Salmonella Typhi
Salmonella paratyphi A + B

36
Q

What is the bacteriology of Typhoid Fever?

A

Salmonella Typhi
Salmonella paratyphi A + B ARE:
Gram negative obligate intracellular organism (i.e. it hangs out in the macrophages)

37
Q

What are the risk factors for severe typhoidal infection?

A

PPI Use
Infection with AMR strain

38
Q

What is the pathophysiology of Typhoid Fever?

A

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

39
Q

In chronic carriers of S. Typhi / S paratyphi, where is the organism likely to sequester?

A

Gall bladder and biliary tree

40
Q

What are the symptoms of TF?

A

Acute Fever, slowly rising over a few days
Faget’s sign
Headache, malaise
Hepatosplenomegaly , abdo distension, mild ascites
Rose Spots

41
Q

What three infectious diseases are known to cause Faget’s sign?

A

Typhoid Fever
Yellow Fever
Brucellosis

42
Q

What is the DDx for Typhoid Fever?

A

You must rule out Malaria and Dengue
Leptospirosis
Brucellosis
Schistosomiasis
Viral GE

43
Q

How do you diagnose Typhoid Fever?

A

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

44
Q

How do you manage Typhoid Fever?

A

** 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

45
Q

What are the complications of Typhoid Fever

A

Complications start to occur >10 after illness starts

Typhoid Encephalopathy (up to 12%)
Nephritis
Hepatitis
UGIB
GI Perf
Dead (CFR 2.5%)§

46
Q

Which country is assocaited with highest number of cases of Multidrug resistant Typhoid Fever?

A

Pakistan

47
Q

Which parasitic co-infection is associated with chronic carriage of Typhoid?

A

Shistosomiasis (unknown why)

48
Q

What is the incubation of typhoid?

A

10-20 days

49
Q

What are the differences between Typhoid and Invasive Non-typhoidal Salmonella?

A

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)

50
Q

What two bacteria are responsible for iNTS?

A

Salmonella Enteritidis
Salmonella Typhimurium

51
Q

What is associated with green watery stool in children?

A

Rotavirus

52
Q

What is associate with rice water stool?

A

Cholera

53
Q

What is mild and severe dehydration in children?

A

5% & 10%

54
Q

Which children are at higher risk of dehydration?

A
  • Children younger than 1 year, particularly those younger than 6 months
  • Infants who had low birth weight
  • Children who have passed more than five diarrhoeal stools in the previous 24 hours
  • Children who have vomited more than twice in the previous 24 hours
  • Children who have not been offered or have not been able to tolerate
    supplementary fluids before presentation
  • Infants who have stopped breastfeeding during the illness
  • Children with signs of malnutrition.
55
Q

How much ORS to give children?

A

Give ORS at 50 mL/kg for fluid deficit replacement over 4 hours and maintenance fluid volume

56
Q

How much fluid to give in a child with a diarrhoeal illness

A

Give extra fluids for ongoing losses: 10 mL/kg per loose stool; 2 mL/kg per vomit.

57
Q

Typhoid causative organism and microbiology facts

A

Salmonella Typhii
Paratyphii A / B / C

Intracellular gram negative flagellated bacillus

58
Q

How is typhoid spread?

A

Faecal oral / contaminated food and water

Peaks in hot season and in flooding

59
Q

Brief pathophysiology of typhoid

A

Mostly killed by stomach acid (worse disease if on PPI)
Uptaken by M cells (Peyer’s patch)
Proliferate in macrophage
Disseminate to bone marrow for more proliferation
Overwhelming bactaraemia

Occuring over 10-20 days incubation

60
Q

Clinical syndrome of typhoid

A

WEEK 1:
Non specific febrile illness with D&V

WEEK 2:
Toxic phase, Faget’s, apathy, rose spots, HSM, abdominal distention

WEEK 3:
Worsening toxicity, delirium, “pea soup” diarrhoea, absent bowel sounds

WEEK 4:
Slow resolution, significant apathy “typhoid facies”

61
Q

What are some complications of typhoid and when do they occur?

A

Death (1%)
GI haemhorrage
Perforation (ulceration at entry site in M / Peyers Patches)

Week 3 most risky but any time from week 2-4

62
Q

How is typhoid diagnosed?

A

CULTURE
Blood: lots needed, not very specific
Bone marrow: more specific than blood (lots of bacteria here remember, they like to divide in marrow)
Stool: unable to differentiate acute vs chronic carriage

Widal agglutination test not recommended

63
Q

How is typhoid managed?

A

Rehydrate, resuscitate etc

Abx: check guidelines, multiple resistant. 1st line = chloramphenicol

Dexamethasone for shock shown to reduce mortality

64
Q

How is typhoid prevented?

A

Identify chronic carriage

Improved WASH

Vaccination:
Oral (attenuated) 3 doses from age of 5
IM (polysaccharide conjugate) 2 doses from age of 6 months

Vaccinate all in endemic areas plus those traveling to the endemic areas

65
Q

How is chronic carriage of typhoid identified and managed?

A

Carriage in gall bladder
Stool culture / bile culture for identification
Treat with abx. Multiple resistance - check guidelines. 1st line = ciprofloxacin

66
Q

Which cancer is associated with chronic typhoid carriage?

A

Cholangiocarcinoma (colonises gall bladder)

Nagasaki Flashcard Extravaganza (34 decks)

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