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2nd Year Med > Lower GI Infection > Flashcards

Lower GI Infection Flashcards

1
Q

define gastroenteritis

A

syndrome characterised by GI symptoms including nausea, vomiting, diarrhoea or abdominal discomfort

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2
Q

define enterocolitis

A

inflammation involving mucosa of small and large intestine

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3
Q

define dysentery

A

blood/pus in stools, usually with abdominal pain and fever

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4
Q

define diarrhoea

A

frequent fluid-like stool (over 3x a day)

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5
Q

what are the manifestations of GI infections?

A

within GI tract:
- toxin effects (cholera)
- inflammation (microbial invastion/shigellosis)

outwith GI tract:
- systemic toxin effects (STEC)
- invasive infection (metastatic salmonella)

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6
Q

what are the barriers to GI infection?

A

mouth (lysozyme)
stomach (acidic pH)
SI (mucous, bile, secretory IgA, peyers patches)
LI (epithelial turnover, normal flora)

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7
Q

describe the normal GI tract flora

A

rich microbiome (100b microbes per gram of faeces)
99% anaerobes
many facultative organisms (enterobacteriales)
protective/metabolic function (carb/protein/fat breakdown)

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8
Q

what are the sources of GI infections?

A

zoonotic - symptomatic animals (salmonella) or asymptomatic shedders (E.Coli)
human carriers (typhoid)
environment/soil contamination (listeria)

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9
Q

how are GI infections transmitted?

A

faecal-oral
food
fluids
fingers/hands
person-to-person

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10
Q

describe diagnostics of GI infections

A

enrichment broth (nutrients promote pathogen growth)
selective media (suppress growth of background flora)
differencial media (pathogen activates indicator)

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11
Q

describe the general treatment of GI infections

A

mild - mostly resolves itself
(hydration maintenance)
more severe/immunocompromised - antibiotics (may have adverse effects)

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12
Q

describe the microbiology and epidemiology of salmonella (enterica)

A
  • gram -ve bacilli
  • enterobacteriales family
  • non lactose fermenters
  • XLD plates used in clinical labs
  • found in cold/warm blooded animals
  • spread through contaminated food (pork/chicken)
  • sometimes water-borne
  • secondary P2P spread possible
  • seasonal peaks (summer/autumn)
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13
Q

describe the pathogenesis and clinical implications of salmonella

A

diarrhoea (invasion/inflammation of SI epithelia)
distant organs may receive metastasis
- incubates for 12-72h
- diarrhoea, vomiting, fever (2-7 days)
fluid replenishment sufficient mostly

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14
Q

describe the microbiology and epidemiology of campylobacter

A
  • curved gram -ve bacilli
  • microaerophilic and thermophilic
  • C.jejuni most important
  • common foodborne infection
  • large animal resevoir (cattle/sheep)
  • season peaks (may/sep)
  • in 70% of retail chicken
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15
Q

describe the pathogenesis and clinical implications of campylobacter

A

inflammation/ulceration/bleeding in SI/LI (bacterial invasion)
bacteraemia can occur (age/IC)
guillain-barre demyelination after (rare)

  • incubation 2-5 days
  • bloody diarrhoea, abdominal cramps, fever (2-10 days)
    fluid replenishment sufficient
    clarithromycin/erythromycin (severe)
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16
Q

explain the microbiology and epidemiology of E.Coli

A
  • gram -ve bacilli
  • enterobacteriales family
  • 6 diarrhhoeagenic groups
  • non-sorbital fermenter (0157)
  • no differencial media available
  • outbreaks/sporadic cases worldwide
  • ‘travellers diarrhoea’
  • infants/children common (developing)
17
Q

describe the pathogenesis and clinical implications of E.Coli

A
  • adherence on lesions/pili
  • action of 1/2 encoded plasmid toxins (ETEC)
  • incubation 1-7 days
  • diarrhoea (blood - EHEC), abdominal pain, vomiting, fever (EPEC), 5-10 days
  • acute renal failure (children, rare)
18
Q

what viruses cause gastroenteritis?

A

norovirus/sapovirus (calciviridae) - affects all ages

rotavirus/adenovirus/astrovirus - mainly affects under 2s, elderly and immunocompromised

19
Q

describe the microbiology of norovirus

A

non-enveloped, single stranded RNA
10 genogroups (G1-10) - only 1/2/4 affect humans
genogroups -> 48 genotypes
common - GII-4

20
Q

describe the epidemiology of norovirus

A

faecal-oral, food, water transmission
small infectious dose (10-100 virions)
1-2 days incubation (shed 3 weeks after infection)
stable (viable for long time)
immunity lasts 6-14 weeks

21
Q

what are the clinical features of norovirus?

A

can be asymptomatic
vomiting, diarrhoea (non bloody), nausea, abdominal cramps, headache/muscle ache, fever, dehydration
lasts 1-5 days

22
Q

what are some possible complications of norovirus?

A

significant portion of childhood hospitalisation
chronic diarrhoea/virus shedding in transplant patients
post-infection complication risk in elderly

23
Q

what are the main treatments for norovirus?

A

oral/IV fluids
antispasmodics
analgesics
antipyretics

24
Q

describe the microbiology and epidemiology of rotavirus

A

double stranded, non enveloped RNA virus
5 strains (G1/2/3/4/9) G1 70%
11 RNA strands (variation)

low infectious dose (10-100 virions)
mainly P2P/faecal-oral
shedding in stool up to 10 days
food/water/resp transmission is possible

25
Q

describe the clinical features of rotavirus

A

incubates 1-3 days
clinical symptoms depend on infection or reinfection (1st infection after 3 months most severe)
diarrhoea, abdominal pain, vomiting, electrolyte loss/dehydration (3-7 days)

26
Q

what are the complications of rotavirus?

A

severe chromic diarrhoea
dehydration/electrolyte imbalance
metabolic acidosis
immunodeficiancy made more severe

27
Q

describe the reinfection of rotavirus

A

antibodies (VP7, VP4, IgA)
1st infection severe, reinfection can occur at any age
90% children have antibodies by age 3 (young children can have up to 5 reinfections)

28
Q

briefly explain adenovirus

A

adenoviridae family
double stranded DNA virus
50 serotypes (variation), 40/41 cause gastroenteritis
fever/watery diarrhoea
no vaccine

29
Q

briefly explain astrovirus

A

single stranded, non enveloped RNA
astroviridae family
less severe gastroenteritis
infections sporadic but outbreaks common in children

30
Q

how are viruses difficult to culture generally tested for?

A

PCR (detects DNA or RNA)
tested from vomit/stool sample

2nd Year Med (18 decks)

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