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Infection > Introduction to Infection and Diarrhoea > Flashcards

Introduction to Infection and Diarrhoea Flashcards

1
Q

Define gastro-enteritis - objective

A

–three or more loose stools/day

accompanying features

Diarrhoea is subjective - fluidity and frequency

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2
Q

Define dysentery

A

–large bowel inflammation, bloody stools

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3
Q

What is the epidemiology of gastroenteritis?

A

•Contamination of foodstuffs
e.g. chicken and campylobacter

•Poor storage of produce

–E.g. Bacterial proliferation at room temperature

  • Travel-related infections e.g. Salmonella
  • Person-to-person spread

–e.g. norovirus

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4
Q

What is the most common cause of gastroenteritis?

A

Viruses are the commonest cause

Campylobacter is the commonest bacterial pathogen

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5
Q

What strain of Ecoli is assocaited with gastroenteritis?

A

Ecoli O157

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6
Q

What are the defenses against enteric infections?

A
  • hygiene
  • stomach acidity

–antacids and infection

•normal flora

–Cl. difficile diarrhoea

•immunity

–HIV- salmonella

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7
Q

What type of diarrhoeal illness is cholera?

A

Non-inflammatory/secretory

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8
Q

What type of diarrhoeal illness is shigella dysentery?

A

Inflammatory

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9
Q

What type of diarrhoeal illness is C.Difficile?

A

Mixed picture

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10
Q

What causes non-inflammatory diarrhoea?

A

–secretory toxin-mediated

  • cholera - increases cAMP levels and Cl secretion
  • enterotoxigenic E. coli (travellers’ diarrhoea)

frequent watery stools with little abdo pain

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11
Q

What is the mainstay of therapy for non-inflammatory diarrhoeal illness?

A

–rehydration mainstay of therapy

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12
Q

What causes inflammatory diarrhoea?

A

Bacterial infection

Amoebic dysentery (marked by dysentery, abdominal pain, and erosion of the intestinal wall)

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13
Q

What are the clinical features of inflamamtory diarrhoeal illness?

A

PAIN

FEVER

Inflammatory toxin damage and mucosal destruction

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14
Q

What is the mainstay of treatment for inflammatory diarrhoeal illness?

A

–antimicrobials may be appropriate but rehydration alone is often sufficient

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15
Q

What does a history of symptoms of gastroenteritis longer than 2 weeks suggest?

A

Unlikely to be infective gastro-enteritis

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16
Q

How do you assess the patient with diarrhoea?

A

•Symptoms and their duration

–>2/52 unlikely to be infective gastro-enteritis

•Risk of food poisoning

–Dietary, contact, travel history

•assess hydration

–postural BP, skin turgor, pulse

•features of inflammation (SIRS)

–fever, raised WCC

Baby may have sunken fontanelle, eyes and cheeks. Few or no tears. Dry mouth and tongue. Decreased skin turgor

Assess electrolytes and fluid losses:

Hyponatraemia due to fluid replacement with hypotonic solutions

Hypokalaemia due to K loss in stool

Investigations:

  • Stool culture
  • Blood culture
  • Renal function
  • Blood count - neutrophilia, haemolysis
  • Abdominal X-Ray if abdomen distended, tender
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17
Q

What is the differential diagnosis for gastroenteritis?

A
  • Inflammatory bowel disease
  • Spurious diarrhoea -secondary to constipation
  • Carcinoma
  • Diarrhoea and fever can occur with sepsis outside the gut
  • lack of abdo pain/tenderness
    goes against gastroenteritis
  • no blood/mucus in stools
18
Q

•Rehydration - iv or oral?

–Oral rehydration with salt/sugar solution

–iv saline

A
19
Q

What is the progression of campylobacter gastroenteritis?

A

7 days incubation period - dietary history may be unreliable

Stools negative within 6 weeks

SEVERE abdominal pain

Less than 1% becomes invasive

Post infection sequale includes guillain-barre syndrome and reactive arthritis

20
Q

What is the progression of disease for salmonella gastroenteritis?

A

–symptom onset usually <48 hrs after exposure

–diarrhoea usually lasts <10 days

–<5% positive blood cultures (more invasive than campylobacter)

–20% patients still have positive stools at 20/52

•Prolonged carriage may be associated with gallstones

–Post-infectious irritable bowel is common

21
Q

Do salmonella bacteria ferment lactose?

A

NO - McConkey agar is pale after culture

22
Q

What are the commonest isolates of salmonella?

A

Salmonella enteritidis

Salmonella typhimurium

23
Q

What isolates cause typhoid?

A

•S. typhi and S. paratyphi cause enteric fever (typhoid and paratyphoid) and not gastro-enteritis

24
Q

How is E.coli O157 spread?

A

From contaminated meat or person-to-person spread

25
Q

What toxin does E.coli produce?

A

Verocyto toxin

Important to note that the toxin can get into the blood but the bacteria can’t

26
Q

What is a common presenting symptom of E.coli O157?

A

Bloody stools

27
Q

What is a risk associated with E.coli O157?

A

Can cause haemolytic-uraemic syndrome (HUS)

–HUS characterised by renal failure, haemolytic anaemia and thrombocytopenia. Treatment supportive – antibiotics NOT indicated

antibiotics may cause lysis of lots of cells and release dangerous amounts of toxins into the blood?

28
Q

What are some other bacteria that cause gastroenteritis?

A
  • Shigella (4 species) – outbreaks of Shigella sonnei in nurseries
  • several other forms of E. coli cause diarrhoea

enteropathogenic

enterotoxic (traveller’s diarrhoea)

enteroinvasive

•routine diagnosis of these E. coli strains not possible – only O157 is easily distinguished from “ordinary” E. coli

29
Q

Occasional causes of food poisoning outbreaks

A
  • Staph aureus (toxin)
  • Bacillus cereus (re-fried rice)
  • Clostridium perfringens (toxin)
30
Q

When are antibiotics indicated in gastroenteritis?

A

–immunocompromised

–severe sepsis or invasive infection

–valvular heart disease

–chronic illness

–diabetes

Not indicated for healthy person with non-invasive infection

31
Q

Which antibiotics are classically associated with c diff?

A

4 C’s:

Cephalosporins

co-amoxiclav

clindamycin

clarithromycin

32
Q

What are the consequences of c diff infection?

A

Mild diarrhoea

Severe colitis (pseudomembranous colitis)

33
Q

What are the toxins that c diff produces?

A

enterotoxin (a)

cytotoxin (b)

34
Q

What is the treatment of c diff infection?

A

Metronidazole

Oral vancomycin

Fidaxomicin (new and expensive)

Stool transplants

Surgery may be required

35
Q

How do we manage C Diff infection?

A

Reduce prescription of broad spectrum antibiotics

Avoid 4 C’s

Antimicrobial management team

Isolate symptomatic patients

Wash hands between patients

36
Q

What is management of Cdiff?

A
  • Stop precipitating antibiotic (if possible)
  • Follow published treatment algorithm – oral metronidazole if no severity markers
  • Oral vancomycin if 2 or more severity markers
37
Q

What parasites are responsible for diarrhoea?

A

Protozoa and helminths

Diagnosis generally by microscopy

•Send stool with request “parasites, cysts and ova please” or P, C and O

UK parasites include Giardia lamblia (metrodonidazole) and cryptosporidium parvum (no treatment) - these are both from contaminated water

38
Q

Which imported parasite is responsible for amoebic dysentery?

A

Entamoeba histolytica

Amoebic liver abscess may be long term complication (anchovy pus)

Treat with metrodonidazole

39
Q

Which viruses can cause diarrhoea?

A
  • Potentially many causes including adenovirus
  • rotavirus in children under 5 yrs
  • common in winter

Noroviruses - common cause of outbreaks - diagnosis by PCR, very infectious

40
Q

How is diagnosis of vral diarhoea made?

A

Antigen detection

41
Q
A

Infection (17 decks)

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