Micro - GI

Question 1

Incubation time

2-8 hrs

Answer 1

Staph

Bacillus cereus

Question 2

Incubation time

8-24 hrs

Answer 2

Vibrio parahaemolyticus
Salmonella
Shigella

Question 3

Incubation time

> 24 hrs

Answer 3

Campyobacter
E. coli
Shigella
Cholera

Question 4

Afebrile, watery diarrhoea, rice water stool

2 days

Answer 4

Vibrio cholera

Cl- efflux causing extensive water and sodium loss in diarrhoea

Fluids, doxy if nec

Question 5

Afebrile (subnormal temps if anything), watery diarrhoea, abdominal pain and cramps and explosive vomiting.

Started 2 hrs after eating some poorly cooked food before washing hands

Answer 5

Staph

Self resolving

Question 6

10 day hx of gradual onset bloody diarrhoea and abdominal pain with flatulence and tenesmus. Histology shows a flask shaped ulcer.

Answer 6

Entamoeba Histolytica

onset usually 1-2 weeks - distinguishes from bacterial dysentery. May also present with fever or weight loss. Symptoms may mimic appendicitis.

Chronic complications include weight loss and liver abscess.

Rx - Met and Paromorycin

Question 7

12 day hx of gradual onset diarrhoea and epigastric pain. Foul smelling stool and flatulence. Recent foreign travel.

Answer 7

Giardia Lamblia

Parasite in duodenum, common with foreign travel. May have malabsorption symptoms - smelly things.

Test with a ‘string test’, treat with Metronidazole

Question 8

1 week, Immunocompromised, watery diarrhoea, bloated

Answer 8

Cryptosporidium parvum

Affects jejunum, supportive

Question 9

3 hr onset, vomit and watery diarrhoea after eating leftover rice. Rice was not heated. Gram +ve rod

Answer 9

Bacillus cereus

Vomiting with heating, d+v without heating

Self limiting

Complications: cerebral abscess and bacteraemia

Question 10

Ingested poorly cooked food. Numbing and tingling started at trunk and progressively moving downwards.

Answer 10

Clostridium Botulinum

Descending paralysis is what differentiates from GBS (ascending)

Treat with antitoxin (great name)

Question 11

8hrs onset watery diarrhoea and abdominal cramps, ate some reheated meat

Answer 11

Clostridium Perfringens

Gram +ve rod. 3rd most common cause of food poisoning (after Camp and Salm). Self resolving.

Complications: gas gangrene - gangrene caused by growth of C perf on muscle tissue where it realeases deadly endotoxins, causing necrosis and gas release (N O H CO2)

Question 12

Pregnant, unpasteurised milk, watery diarrhoea, positive bile aesculin test

Answer 12

Listeria

Gram +ve rod, aesculin positive - turns sample black

Rx: Amp

Question 13

Enterobacteria - how to differentiate (all gram -ve)

Answer 13

E coli - rod, glucose or lactose fermenters, oxidase negative

Salmonella - rod, not fermenter, oxidase negative, flagella

Shigella - rod, not fermenter, non motile, oxidase neg

Vibrio - comma, late lactose fermenters, oxidase pos

Campylobacter - S shaped, non fermenter, motile, oxidase pos

Question 14

3 day hx of bloody diarrhoea after coming back from holiday.

Answer 14

E coli

gram -ve rod oxidase neg, lactose fermenting

assoc HUS, self limiting

Question 15

3 day hx of bloody diarrhoea after eating eggs

Answer 15

Salmonella

gram -ve rod oxidase neg, non fermenting. Causes inflammatory enterocolitis

self limiting but can treat with cipro if v bad

Question 16

Returning traveller, fever and abdominal discomfort and constipation

Answer 16

Typhoid

Can become systemic - splenomegaly, rose spots (red spotty rash)
Anaemia, leucopenia (with normal neutrophils - balanced out), bradycardia. Positive on blood cultures

Rx: Ceftriaxone

Question 17

2 day hx of severe bloody and mucousy diarrhoea. Fever and pain

Answer 17

Shigella

gram -ve rod, non motile, non fermenter, oxidase negative

Produce shiga toxin, only requires a small amount to cause massive effect.

Avoid abx but use Cipro if must

Question 18

Seafood Japan diarrhoea for 3 days

Answer 18

Vibrio parahaemolyticus

self limiting

Question 19

Shellfish handlers, causing very nasty rash on skin

Answer 19

Vibrio Vulnificus

cellulitis in shellfish handlers, fatal septcaemia and D+V with HIV

Question 20

3 weeks of uncomfortable bloody diarrhoea with foul smell

Answer 20

Campylobacter

3 weeks gives it away. S shaped and oxidase positive.

Self limiting, but treat in immunocompromised - macrolide/cipro

Complications - GBS, reactive arthritis

Question 21

Fever, abdominal pain, bloody diarrhoea with systemic signs. Red lumps on shins, and joint pain

Answer 21

Yersinia enterocolitis - gram -ve bacillus

‘Psuedo TB’ - presents similar but more aggressive. Also causes mesenteric adenitis with caseating granulomas.

Self limiting but treat aggressively if systemic disease with doxy/gent