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Year 3 - infection > Infectious Diarrhoea - Part 2 > Flashcards

Infectious Diarrhoea - Part 2 Flashcards

1
Q

How is a routine bacterial culture used for Bacterial Gastroenteritis?

A
  • difficult to find pathogen in the midst of complex normal flora
  • selective and enrichment methods of culture necessary - variety of media and incubation conditions
  • takes 3 days to complete all tests
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2
Q

How is Routine Bacterial Culture Campylobacter done?

A
  • specialised culture conditions
  • C. jejuni/ C. coli

Very particular culture conditions

Like body temperature and above which is higher than most other bacteria

Likes lower oxygen levels

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3
Q

Routine Bacterial Culture - Campylobacter

is it common?

A

commonest cause of bacterial food poisoning in UK

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4
Q

Routine Bacterial Culture - Campylobacter

what causes it?

A

chickens, contaminated milk, puppies

isolated cases rather than outbreaks

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5
Q

Routine Bacterial Culture - Salmonella

how many types is there?

A
  • 2 species recognized: Salmonella enterica, Salmonella bongori
  • thousands (!) of serotypes with individual names
  • traditionally named after place of first isolation
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6
Q

Routine Bacterial Culture - Salmonella

how is it tested for?

A

Isolation in the laboratory

screened out as lactose non-fermenters (E. coli ferments lactose and salmonella doesn’t ferment lactose)

serotyping antigen and biochemical tests

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7
Q

Routine Bacterial Culture
Common Salmonella Infections in UK

what are the commonest isolates and where do they come from?

A
  • Commonest isolates are Salmonella enteritidis and Salmonella typhimurium
  • > 50% of these imported from abroad
  • N.B. - S. typhi and S. paratyphi cause enteric fever (typhoid and paratyphoid) and not gastro-enteritis
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8
Q

what are some other bacteri that may be the cause?

A
  • Shigella (4 species) - outbreaks of Shigella sonnei in nurseries
  • E.coli - part of normal gut flora, most strains non pathogenic - several forms of E. coli cause diarrhoea
  • enterohaemorrhagic
  • enterotoxic (traveller’s diarrhoea)
  • enteroinvasive
  • enteropathogenic

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

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9
Q

What are some other occasional causes of food poisoning outbreaks?

A
  • Staph aureus (toxin)
  • Bacillus cereus (re-fried rice)
  • Clostridium perfringens (toxin)
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10
Q

Clostridioides (formerly Clostridium) difficile diarrhoea - how do patient usually present?

A

Patient usually gives history of previous antibiotic treatment – the “4 C antibiotics”

Severity ranges from mild diarrhoea to severe colitis

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11
Q

what are the 2 different toxins that C. diff produces?

A

C. Diff produces enterotoxin (A) and cytotoxin (B) (inflammatory)

Tox B is the major driver of inflammation

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12
Q

what is the treatment of C. diff

A
  • Metronidazole
  • oral vancomycin - Can use oral vancomycin to treat, vancomycin isn’t usually given orally as it is minimally absorbed into the systemic circulation
  • Fidaxomicin
  • Stool transplants
  • surgery may be required - Surgery may be required if extremely severe
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13
Q

Pseudomembranous colitis

Pseudomembranous colitis refers to swelling or inflammation of the large intestine (colon) due to an overgrowth of Clostridioides difficile (C difficile) bacteria. This infection is a common cause of diarrhea after antibiotic use

A

Mucosal surface of the gut

Inflammation over the mucosa

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14
Q

what is the prevention of CDI?

A
  • Reduction in broad spectrum antibiotic prescribing
  • Avoid 4 Cs – cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin
  • Antimicrobial Management Team (AMT) and local antibiotic policy
  • Isolate symptomatic patients
  • Wash hands between patients
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15
Q

what is the management of CDI?

A
  • Stop precipitating antibiotic (if possible)
  • Follow published treatment algorithm – oral metronidazole if no severity markers
  • raised temp > 38.5
  • WCC >15
  • acute rising creatinine
  • suspicion of colitis/ileus/toxic megacolon

• Oral vancomycin if 2 or more severity markers

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16
Q

what are different kinds of parasites?

A

• Protozoa and helminths

One cell animal – protozoa

Helminths – worm, can be seen by naked eye

17
Q

how od you diagnose a parasite?

A
  • Diagnosis generally by microscopy
  • Send stool with request “parasites, cysts and ova please” or P, C and O

If suspect parasite then look at stool sample under microscope

18
Q

Giardia lamblia (aka G. duodenalis/intestinalis) - protozoa

this is a uk parasite, what does it cause?

A
  • Giardiasis - abdominal cramps, bloating, nausea and bouts of watery diarrhoea, malabsorption and failure to thrive
  • exist in two forms: cysts, trophozoites
  • Cysts - intermittent on stool microscopy; trophozoites - diarrhoea specimen, duodenal biopsy or “string test” (gelatin capsule on absorbent string - swallowed and withdrawn)
19
Q

Giardia lamblia (aka G. duodenalis/intestinalis) - protozoa

this is a uk parasite, how do you get it?

A

• contaminated water (ingestion)

20
Q

Giardia lamblia (aka G. duodenalis/intestinalis) - protozoa

this is a uk parasite, what is the treatment?

A

• treat with metronidazole

21
Q

Cryptosporidium parvum (protozoa) is a uk parasite

what forms is there of it

A

exist in two forms: oocysts, trophozoites

22
Q

Cryptosporidium parvum (protozoa) is a uk parasite

what does it cause?

A

Cryptosporidiosis - watery diarrhoea, nausea and vomiting, abdominal cramps, low grade fever

23
Q

Cryptosporidium parvum (protozoa) is a uk parasite

how is it caused?

A

ingestion of oocysts in faecally contaminated water

24
Q

Cryptosporidium parvum (protozoa) is a uk parasite

what is the investigation and treatment?

A
  • oocysts stool specimen seen on microscopy
  • no specific treatment usually required

Just rehydration

Can be difficult to eliminate if the patient is immunosuppressed

25
Q

what are examples of Imported parasites? their effects and their treatment?

A
  • large range of possibilities
  • Entamoeba histolytica
  • Protozoa - exist cyst, trophozoite forms
  • amoebic dysentery - bloody diarrhoea
  • microscopic examination for trophozoites (symptomatic pt) “hot stool”; cysts (asymptomatic patient)
  • amoebic liver abscess may be long term complication (“anchovy pus”) – trophozoites multiply in liver cells
  • treat with metronidazole (trophozoites); diloxanide furoate (cysts in intestine lumen)
26
Q

what are the causes of Viral Diarrhoea?

A
  • rotavirus in children under 5 yrs – vaccine UK 2013 8 & 12 weeks (rotavirus cases reduced by aprox 70%)
  • common in winter
  • certain strains of adenovirus (40/41) also cause diarrhoea
27
Q

how do you diagnose viral diarrhoea?

A

• diagnosis of both possible by antigen detection - rapid test

Both can be detected with antigen detection test

28
Q

• Noroviruses – named after Norwalk, Ohio (first identified)

  • Norwalk like viruses
  • Winter vomiting disease

what does it cause?

A
  • Diarrhoea and vomiting
  • common cause of outbreaks: hospital, community, cruise ships
29
Q

is norovirus infectious?

A
  • very infectious - infectious dose only 18 virus particles (1g faeces may shed 5 billion infectious doses)
  • ward closures common - staff and patients affected
  • strict infection control measures needed - alcohol gel not effective measure; isolation
30
Q

how do you diagnose norovirus?

A

• diagnosis by PCR

31
Q

Summary:

  • the laboratory investigation of bacterial gastroenteritis: Campylobacter, Salmonella, E.coli
  • Parasitic diarrhoea: Giardia, Cryptosporidium, Entamoeba histolytica
  • Viral diarrhoea: rotavirus, adenovirus, norovirus
A

Year 3 - infection (14 decks)

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