Microbiology 6 - GI infections

Question 1

In a febrile patient with a GI infection, what are the key differentials?

Answer 1

1. Inflammatory diarroea

2. If no diarrhoea - enteric fever (typhoid/ salmonella)

Question 2

In an afebrile patient with a GI infection, what is the top differential?

Answer 2

Secretory diarrhoea due to toxins (eg cholera)

Question 3

What is the incubation period of campylobacter?

Answer 3

1-10 days

Question 4

What is the incubation period of bacilus cereus?

Answer 4

1-6 hours

Question 5

Why does staph aureus food poisoning produce such rapid symptoms?

Answer 5

Toxin is pre-formed

Question 6

What are the key cytokines involved in Staph aureus food poisoning?

Answer 6

IL-7 and IL-2

Question 7

Describe the symptoms of S aureus food poisoning

Answer 7

Vomiting

Waterey, non-bloody diarrhoea

Question 8

Describe the different toxins produced by bacilus cereus

Answer 8

Heat-stable toxin causes emesis
Heat-labile toxin causes diarrhoea
Only the heat-labile toxin is destroyed upon heating

Question 9

Describe the diarrhoea produced by bacilus cereus

Answer 9

Waterey, non-bloody

Question 10

In what type of food might clostridia botulinum be found?

Answer 10

Honey

Question 11

What type of clostridia spp causes food poisoning?

Answer 11

Clostridia perfringens

Question 12

In what sort of food is clostridia perfringens found?

Answer 12

Re-heated meat

Question 13

Which organism causes pseudomembranous colitis?

Answer 13

Clostridium difficile

Question 14

Which diarrhoeal disease is associated with antibiotic use?

Answer 14

Pseudomembranous colitis caused by C. difficile

Question 15

What type of symptoms does listeria monocytogenes poisoning cause?

Answer 15

Febrile gastroenteritis

Waterey diarrhoea

Question 16

Recall 2 sources of listeria poisoning

Answer 16

Unpasteurised dairy 
Refringerated foods (eg sandwiches)

Question 17

Is listeria alpha or beta haemolytic?

Answer 17

Beta haemolytic

Question 18

What is the causative organism in ‘traveller’s diarrhoea’?

Answer 18

Enterobacteriacae (usually the toxogenic form, ETEC)

Question 19

What organism causes haemolytic uraemic syndrome?

Answer 19

EHEC enterobacteriacae

Question 20

Recall one very important thing to avoid in the management of enterobacteriacae poisoning

Answer 20

Antibiotics

Question 21

Recall 3 worrying species of salmonella

Answer 21

S typhi
S enteritidis
S cholerasuis

Question 22

What symptoms are caused by S typhi infection?

Answer 22

Bactaraemia
Constipation and fever
Splenomegaly and ROSE SPOTS

Question 23

What are the 2 key forms of shigella that cause disease in humans?

Answer 23

S dysenteriae
S flexneri (associated with MSM)

Question 24

What disease pattern does shigella infection cause?

Answer 24

Dysentry

Question 25

How should shigella infection be managed?

Answer 25

Avoid antibiotics

If really necessary, go for ciprofloxacin

Question 26

What is the typical stool appearance in Vibrio cholerae infection?

Answer 26

Rice water

Question 27

Which organism is most likely to cause cellulitis in a scuba diver?

Answer 27

Vibrio vulnificus

Question 28

On what sort of agar can vibrio spp be grown?

Answer 28

Salty agar

Question 29

For how long can campylobacter symptoms last?

Answer 29

Up to 20 days

Question 30

What is one key serious complication of campylobacter infection?

Answer 30

Guillan Barre syndrome

Question 31

What is the symptom of “flask-shaped ulcer” pathognemonic for?

Answer 31

Entamoeba histolytica infection

Question 32

What symptoms does E. histolytica infection cause?

Answer 32

Dysentry and flatulence

Question 33

How should E. histolytica infection be managed?

Answer 33

Metronidazole

Question 34

How can giardia infection be investigated?

Answer 34

String test

Question 35

How should giardia infection be treated?

Answer 35

Metronidazole

Question 36

In which patient group does cryptosporum parvum cause symptoms, and what are those symptoms?

Answer 36

The immunocompromised

Severe diarrhoea