Microbio - GI infections

Question 1

Most common travellers’ diarrhoea?

Answer 1

E coli

Question 2

most common bloody travellers’ diarrhoea

Answer 2

Shigella

Question 3

Bacteria with incubation period <6 hours?

Answer 3

B. Cereus + S. Aureus

Question 4

Which bacteria is assoc with reheated rice? Incubation period? presentation?

Answer 4

Bacillus Cereus
<6 hours incubation period
VOmiting + watery non-bloody diarrhoea

Question 5

Pear shaped trophozoite w 2 nuclei?

Answer 5

Giardia lamblia

Question 6

Presentation of giardia?

Answer 6

Foul smelling non-bloody diarrhoea (malabsorption of protein and fat)

Question 7

Which protozoan causes severe diarrhoea in immunocompromised?
What is seen in the stool?

Answer 7

Cryptosporidium parvum

Oocysts seen in stool

Question 8

Reportable GI infections?

Answer 8

Salmonella
Shigella
E Coli O157
Listeria
Campylobacter
Norovirus

Question 9

3 subspecies of Clostridia?

Answer 9

Botulinum
Perfringens
Difficile

Question 10

Clostridia Botulinum - how is it picked up?

Pathophysiology? Presentation?

Answer 10

Canned/vacuumed food + honey in kids

Blocks ACh release from peripheral nerves
Presentation: descending paralysis (diff to Guillan Barre)

Question 11

Tx of C botulinum

Answer 11

Antitoxin

Question 12

C Perfringens - how is it picked up? Pathophysiology? Presentation and duration? Complication?

Answer 12

Reheated meats
- superantigen enterotoxin –> binds directly to TCR and MHC –> huge cytokine release

WATERY diarrhoea + cramps for 24 hours.

Complication: gas-gangrene

Question 13

Tx of C difficile. Complication of C difficile infection?

Answer 13

Stop abx
start vancomycin. 2nd line = metronidazole

Pseudomembranous colitis

Question 14

B. Cereus - gram stain findings?

How does it cause diarrhoea?

Answer 14

Gram +ve rods

2 toxins: HEAT STABLE EMETIC + HEAT LABILE DIARRHOEAL TOXIN

Question 15

Staph aureus: virulence factor?
Microbe features?
How does it cause diarrhoea?
Duration of illness

Answer 15

Protein A = main virulence factor

• Catalase and Coagulase +ve. Beta haemolytic
• produces enterotoxin w superAg –> IL1 + IL2 release
• <1 day

Question 16

Subtype of E coli which is most common cause of travellers diarrhoea?
Pathophysiology?
Where does it act?

Answer 16

ETEC (toxigenic)

Heat labile toxin = activates AC + cAMP.
Heat stable toxin = activates GC

• Acts on SI and NOT the colon.

Question 17

subtypes of E Coli - name 3 which aren’t ETEC… what are they characterised by

Answer 17

EHEC - haemorrhage, caused by verotoxin. causes HUS
EIEC - invasive dysentry
EPEC - paediatric diarrhoea

Question 18

2 types of Salmonella - what do they cause?

Answer 18

Salmonella typhi = enteric fever

Salmonella ENTERITIDES = enterocolitis

Question 19

6 clinical features of salmonella typhi infection?

Answer 19

Slow onset fever + Constipation
Relative bradycardia
Splenomegaly
Rose spots
Low WBCs

Question 20

Tx of salmonella typhi?

Answer 20

Ceftriaxone

Question 21

Salmonella enteritides
- how is it transmitted?
Presentation?
tx?

Answer 21

Poultry, eggs, meat
Invades SI and LI –> Non-bloody diarrhoea
Ciprofloxacin

Question 22

Salmonella - H2S?

Answer 22

H2S producer

Question 23

Shigella

• motility? H2S?
• presentation?
• pathophysiology?
• important subtype?

Answer 23

Shigella

• non motile, non H2S producer
• Bloody diarrhoea, fever
• Shiga enterotoxin = v effective!
• S. flexneri = common in MSM (men who have sex with men)

Question 24

Which GI infection is associated w necrotising granulomas and reactive arthritis?

Answer 24

Yersinia enterocolitis

Question 25

Name 2 GI infections which prefer 4C?

Answer 25

Yersinia and Listeria monocytogenes

Question 26

Yersinia enterocolitis - transmission?
Clinical features?
Associations?

Answer 26

• Food contaminated by animal excrement
• Enterocolitis + mesenteric adenitis w necrotising granulomas
• Assoc with reactive arthritis + erythema nodosum.