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Infection Term 4 > 4.2- GI Infections > Flashcards

4.2- GI Infections Flashcards

1
Q

What are enteric bacteria?

A
  • Form a group of related bacteria that were known to reside in, and were first isolated from the mammalian intestine
  • gram NEGATIVE so have LPS
  • endotoxin therefore part of bacteria’s structure
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2
Q

When do enteric bacteria become pathogenic?

A

when they acquire virulence factor

  • found in soil, water and vegetation
  • can originate from an animal or from a human carrier or through the endogenous spread of organisms
  • resistance to bile salts
  • some have capsules
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3
Q

Name some examples of enteric bacteria?

A
  • salmonella typhi
  • shigella species
  • yersinia pets
  • E. coli
  • klebsiella pneumoniae
  • proteus mirabilis
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4
Q

What is salmonella and where is it found?

A
  • gram negative, facultative, flagellated rod-shaped bacterium belonging to family Enterobacteriaceae
  • live in intestinal tracts of warm and cold-blooded animals
  • aerobic
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5
Q

What two diseases does salmonella mainly cause?

A

1) Enteric fever (typhoid): resulting from bacteria invasion of the bloodstream
2) Acute gastroenteritis: resulting from a food borne infection/ intoxication

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6
Q

What are the types of salmonella?

A

S. type: causes typhoid fever
S. paratyphoid A, B & C-cause paratyphoid fevers
S typhimurium, S.montevideo, S.wien- causes salmonellosis

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7
Q

How is salmonella classed?

A

-Kaufmann-White scheme

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8
Q

Describe the events of salmonellosis

A

-gotten from ingestion of contaminated food

-humans ingest salmonella
-attaches to epithelial cells
-induces phagocytosis
-salmonella multiply within phagocytic vacuole
-salmonella kills host cell, inducing diarrhoea
you get BACTEREMIA; salmonella moves into bloodstream

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9
Q

What is salmonella typhi?

A

humans are the only host

  • causes typhoid fever
  • infection occurs via ingestion of food or water contaminated with sewage containing bacteria from carriers
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10
Q

What is the infective mechanism of salmonella typhi?

A
  • after ingested, the bacteria temporarily enter bloodstream and travel to the small intestine
  • white blood cells carry the disease to liver, spleen and bone marrow where it reproduces and re-enters the blood stream
  • the bacteria then invades the gallbladder, biliary system and the bowel lymphatic tissue.
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11
Q

What organs are infected in the abdominal cavity?

A
  • liver
  • gallbladder
  • stomach
  • small intestine
  • large intestine
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12
Q

How many stages are there of typhoid fever?

A

4

-each lasts a week

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13
Q

Describe stage 1 of typhoid fever

A
  • slowly rising temperature
  • bradycardia, malaise, headache or cough
  • epistaxis in 25% of cases
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14
Q

Describe stage 2 of typhoid fever

A
  • continuing high fever
  • extremely distended abdomen bc HIGH inflammatory response
  • considerable weight loss
  • bradycardia continues
  • dicrotic pulse wave
  • delirium
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15
Q

Describe stage 3 of typhoid fever

A

Complications:

  • intestinal haemorrhage due to bleeding, bc epithelia is breaking down further
  • intestinal perforation
  • encephalitis (inflammation of brain)
  • high fever
  • dehydration and increasing delirium
  • lies motionless with eyes half-opened
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16
Q

Describe stage 4 of typhoid fever

A

defervescence ie very high fever

continues into the fourth week

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17
Q

Name some complications of typhoid fever

POPKII

A

death from:

  • pneumonia
  • overwhelming infections
  • peritonitis
  • kidney failure
  • intestinal bleeding
  • intestinal perforation
18
Q

What advantage do people with CF have?

A

higher resistance to developing salmonella and typhoid

19
Q

What does it mean to be a typhoid carrier?

A

a healthy person who survived the disease but in whom bacteria are able to survive w/o causing further symptoms
-continue to spread disease through their excrement without realising it

20
Q

How do you treat typhoid carriers?

A
  • treat w prolonged antibiotics

- removal of gallbladder or the site of infection usually cures patient

21
Q

What is SHIGELLOSIS?

A

bacterial gastroenteritis

  • gram negative rods
  • nonmotile
  • non-spore forming
  • catalase positive
  • oxidase negative
  • facultatively anaerobic
  • infects GI tracts
22
Q

What are the four species of shigellosis?

BDSF

A
  • boydii
  • dysenteriae ( causes deadly epidemics)
  • flexneri
  • sonnei
23
Q

Why is shigellosis non-motile?

A

therefore do not have H antigen

because no flagella to move

24
Q

Name 5 differences between diarrhoea and dysentery?

A

-diarrhoea is a watery stool with no blood/mucus
dysentery is a mucoid stool, may be accompanied by blood

  • diarrhoea affects small bowel, dysentery affects colon
  • fever is less common in diarrhoea but more common in dysentery

-diarrhoea is mostly viral ( can also be caused by E. coli if watery)
dysentery is mostly bacterial eg E.coli, shigella and salmonella

25
Q

Describe the infective mechanism of shigella?

A

normally via direct person-to-person transmission only
(or through contaminated food/water)
-enters GI system and attaches to epithelial cells of colon
-triggers phagocytosis through surface antigen
-multiplies in cytosol
-releases a chemical that breaks down actin fibres
-causes connections between cells to break down and allows bacteria to evade immune defences
- mucosal abscesses form and epithelial cells are killed by infection
-shigella that enters the blood is completely phagocytized

26
Q

How is shigellosis treated?

A

-treat dehydration
patients with severe dysentery are treated with antibiotics eg ampicillin
-in contrast to salmonella, patients respond to antibiotic therapy and disease duration is diminished.

27
Q

What is shigellosis characterised by?

A
  • bloody faeces
  • intestinal pain
  • incubation period of 1-3 days
28
Q

What are some virulence factors of shigella?

A

-enterotoxins eg shigatoxin

29
Q

Name 3 antimicrobials used to treat shigella? (TCA)

A

TMP-SMX (resistance is common)
Ciprofloxacin
Azithromycin

30
Q

What conditions does E.coli cause?

A
  • bacteremia
  • UTI’s
  • Neonatal meningitis
  • Intra-abdominal infections ( associated w intestinal perforation)
31
Q

What are the 4 main strains of E. coli? TPIH

A

1) ETEC- enteroToxigenic
2) EPEC- enteroPathogenic
3) EIEC- enteroInvasive
4) EHEC-enteroHaemorrhagic

32
Q

What is ETEC?

A

ETEC- enteroToxigenic
produces 2 exotoxins; HLT ( heat labile toxin) and heat stable toxin (ST)
watery osmotic diarrhoea , non-invasive and no fever

33
Q

What is EPEC?

A

enteropathogenic

  • moderately invasive
  • similar to shigella bc it has a Shiga toxin
34
Q

What is EIEC?

A

enteroinvasive
dysentery, causes host response

clinically identical to shigella

35
Q

What is EHEC?

A

enterohaemorrhagic

0157: H7 strain
- shiga toxin
- inflammatory response
- can cause haemolytic uraemic syndrome (HUS)

36
Q

What is the O 157: H7 strain?

A

most common severe

37
Q

What is the O 157: H7 strain?

A

most common severe E.coli strain

causes severe diarrhoea and sometimes kidney damage

38
Q

Define diarrhoea

A

Abnormal faecal discharge characterised by frequent and/or fluid stool; usually resulting from disease of the small intestine and involving increased fluid and electrolyte loss

39
Q

How do different types of diarrhoea help you classify the disease?

A
  • if without blood or pus then due to enterotoxin production

- if with blood and pus, invasive infection with mucosal destruction

40
Q

Define dysentery

A

An inflammatory disorder of the gastrointestinal tract often associated with blood and pus in the faeces and accompanied by symptoms of pain, fever, abdominal cramps; usually resulting from disease of the large intestine

41
Q

Define enterocolitis

A

Inflammation involving the mucosa of both the small and large intestine

Infection Term 4 (8 decks)

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