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Microbiology > GI infections > Flashcards

GI infections Flashcards

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Biology 101 flashcards
1
Q

What are the 3 types of GI infection?

A
  1. Secretory diarrhoea = Bowel changes + no fever (Cholera)
  2. Inflammatory diarrhoea = Bowel changes + fever (Campylobacter, Shigella)
  3. Enteric fever = Mainly severe fever (Salmonella typhi)
  • Secretory not inflammatory so doesn’t produce fever - doesn’t invade the mucosa (e.g. cholera binds to Cl- channel)
  • Inflammatory / enteric are inflammatory - invade mucosa, produce cytokines etc.
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2
Q

Catalase positive

A

S aureus

vs. Strep - catalase negative

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3
Q

Heat-labile pre-formed toxin
Food preparers spread (1/3 of population carry)
Secretory diarrhoea within 4h, resolves in 24h
TSST-1 superantigen = toxic-shock
Self-limiting

A

S aureus

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4
Q

Heat stable + heat-labile toxins
Rice water stool
Reheated rice
Spores

A

Bacillus cereus

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5
Q

3 types of clostridium

A

Botulinum
Perfringens
Difficile

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6
Q 
Botulism
Honey, canned + vacuum-packed products
Pre-formed toxin blocks ACh release
Dry mouth + visual disturbance then bilateral descending paralysis + death
Treat with antitoxin
A

Clostridium botulinum

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7
Q

Pre-heated foods (curry from hot plate)

Gas gangrene

A

Clostridium perfringens

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8
Q

Pseudomembranous colitis (post-Abx diarrhoea)
Following Abxs (3Cs - cephalosporins, cipro, clinda)
Gram positive anaerobic rod
Spreads really easily due to profuse diarrhoea

A

Clostridium difficile

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9
Q

What is the mechanism of pseudomembranous colitis?

A

Occurs following Abx use pt. 3Cs (cephalosporins, cipro, clinda)
Imbalance in normal gut flora
Clostridium difficile
Acute onset watery diarrhoea 4-9 days post-Abx
Exudative material creates ‘pseudomembrane’

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10
Q

What is the treatment for pseudomembranous colitis?

A

Oral metronidazole for 10-14d (sits in bowel)

If fails vancomycin

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11
Q 
Aesculin positive
B-haemolytic
Tumbling motility 'tumbleweed'
Unpasteurised dairy
Ampicillin treatment
A

Listeria monocytogenes

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12
Q

What are the 5 main enterobacteriae infections?

A
  • ETEC
  • EIEC
  • EHEC
  • HUS
  • EPEC
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13
Q

What can enterobacteriae infections be treated with?

A

Ciprofloxacin

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14
Q 
Enterobacteriae
Gram and oxidase negative
Facultative anaerobe
Traveller
Heat labile (stim adenyl cyclase, cAMP), heat stable (stim GC)
A

E coli (ETEC)

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15
Q

(Enterobacteriae
Gram and oxidase negative
Facultative anaerobe)
Dysentery, like shigella

A

E coli (EIEC)

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16
Q

(Enterobacteriae
Gram and oxidase negative
Facultative anaerobe)
Haemorrhagic

A

E coli (EHEC)

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17
Q

(Enterobacteriae
Gram and oxidase negative
Facultative anaerobe)
Paediatric diarrhoea in newborn nurseries

A

E coli (EPEC)

18
Q 
(Enterobacteriae
Gram and oxidase negative
Facultative anaerobe)
Swimming in open water, petting zoos
0157-H7 toxin
MAHA, thrombocytopenia, renal failure
A

E coli (HUS)

19
Q 
Non-lactose fermenters
H2S black colonies
TSI agar
Selenite F broth
3 toxins - O, H, Vi
A

Salmonella

20
Q

What are the 3 types of salmonella toxin?

A

O - cell wall
H - flagellar
Vi - capsular

21
Q

What are the 2 main salmonella?

A

Enterides

Typhi (enteric fever)

22
Q 
Multiplies in Peyer's patches
Rose spots
Slow onset fever + constipation
Relative bradycardia
Ceftriaxone
A

Salmonella typhi (enteric fever)

23
Q

Poultry eggs and meat e.g. BBQ
Non-bloody diarrhoea
Usually self-limiting

A

Salmonella enterides

24
Q 
Non-motile
H2S producers
Shiga enterotoxin
Distal ileum + colon
Bloody diarrhoea
Sonnei, dysenteriae, flexneri (MSM)
A

Shigella

25
Q 
Curved comma-shaped oxidase positive
Rice water stool
Shellfish, oysters, shrimp
Enterotoxin with A + B sub-units
Rehydration therapy
Supportive
A

Vibrio cholera

26
Q

How does cholera cause rice water stool?

A

Enterotoxin has A (active) and B (binding) sub-units
B binds to GM1 on epithelial cells
A activates cAMP intracellularly - active secretion of chloride and sodium ions - osmotic pull of water

27
Q

Curved comma-shaped oxidase positive
Eating raw or undercooked seafood in Japan
Doxycycline

A

Vibrio parahaemolyticus

28
Q

Curved comma-shaped oxidase positive
Shellfish handler scratched by coral
Cellulitis then fatal septicaemia with D+V
Doxycycline

A

Vibrio vulnificus

29
Q

Curved S shaped oxidase positive
Microaerophilic, mobile
Get Guillain-Barre, reactive arthritis (Reiter’s) after diarrhoea
Unpasteurised milk, poultry (chickens pecking milk bottles)
Super bad bloody foul smelling diarrhoea
(Can treat erythro or cipro but symptoms usually gone by the time results get back)

A

Campylobacter jejuni

30
Q

S-shaped vs. comma-shaped

A

S-shaped - campylobacter

comma-shaped - vibrio (cholera)

31
Q

Peyer patch invasion - mesenteric LN enlargement - then invades
Necrotising granulomas
3Ps - pericarditis, peritonitis, pharyngitis
Cold enrichment

A

Yersinia enterocolitica

32
Q

Immunosuppressed

Sub-Saharan Africa

A

TB

33
Q

Food, water, soil
MSM
Motile trophozoite in diarrhoea / non-motile cyst if no diarrhoea
Flask shaped ulcer
Water filters, boiling water whilst camping
RUQ pain from liver abscess

A

Entamoeba histolytica

34
Q

Pear shaped trophozoite
Fould smelling steatorrhoea containing cysts
Excessive flatulence, bloating, explosive diarrhoea
Mental hospitals, travellers

A

Giardia lamblia

35
Q 
Kinyoun acid fast stain - cysts
Severe diarrhoea in young child
Swimming pool parties or rivers in slums
Jejenum
Paromomycin Tx
A

Cryptosporidium parvum

36
Q

Main protozoa in GI disease

A

Entamoeba histolytica
Giardia
Cryptosporidium

37
Q

Main viral in GI disease

A

Norovirus
Rotavirus
Adenovirus

38
Q

What bacterial vaccines are available?

A

Cholera
Campylobacter
ETEC
Salmonella Typhi

Only given if going to endemic area or high risk in terms of army / MSF volunteer for example

39
Q

What viral vaccines are available?

A

Rotavirus

40
Q

What bugs can metronidazole be used to treat?

A

(GET you difficult bugs)

Giardia, Entamoeba, Trichomonas, C difficile

41
Q

Story to remember vancomycin action

A

Treats Gram positive
Ambulance is ‘Van’ with big red cross on it
Give IV as cannot pass through lining of intestine…but in C difficile give orally as just has to stay in gut so localises
Side effect = Red Man Syndrome - driver of ambulance with red face (sudden erythematous pruritic rash on face / neck / torso)

Microbiology (19 decks)

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