Pathogens of GI Tract

Question 1

What is dysentery?

Answer 1

Abnormal inflammation of GI - blood and pus in faeces - often disease of the large intestine

Question 2

What organisms can cause food poisoning?

Answer 2

Staph aureus
Bacillis cereus
Clostridium botulinum

Question 3

How/ what kind of food poisoning does staph.aureus produce?

Answer 3

Mainly in dairy - gram +ve
50% strain have heat-stable enterotoxin - also resistant to stomach acid/ digestive enzyme
3-6hr severe vomit

Question 4

How/ what kind of food poisoning does bacillus cereus cause?

Answer 4

Associated rice - toxins remain active

Gram+ve spore former

Question 5

How/ what kind of food poisoning does clostridium botulism produce?

Answer 5

Heat stable toxin ingested in food - gram +ve

Flaacid paralysis w/ neurological symptoms

Question 6

What is helicobacter pylori and describe virulence?

Answer 6

Anaerobic gram -ve
Produce urease - convert urea –> ammonia and CO2
Cause increase pH - protective cloud during transit to mucin layer (allows to reside in mucosal tissue - cause bleeding/ ulceration)

Question 7

Tx of peptic ulcers?

Answer 7

Tx w/ PPI

Ab: metronidazole and amoxicillin

Question 8

What strain is linked to peptic ulcers and cancer?

Answer 8

cagA +ve strain

Question 9

What does E. coli cause?

Answer 9

Gram -ve motile rod causing diarrhoeal diseases

Question 10

How to detect E.Coli?

Answer 10

MacConkey agar - yellow agar turned pink based on fermentation of lactose
PCR - serotype

Question 11

What is EPEC?

Answer 11

Enteropathogenic e.coli - inject protein into host to manipulate cytoskeleton
Bundle-forming pili important in attachment
Common cause travellers diarrhoea - no blood

Question 12

What is EIEC?

Answer 12

Enteroinvasive e.coli

Invade and destroy epithelial cells - blood

Question 13

What is EHEC?

Answer 13

Enterhaeamorrhagic e.coli
Production Vero-toxin - acts via directly damaging cells and cause haemorragic colitis
Can spread to kidneys

Question 14

What is shigella?

Answer 14

Shiga toxin - common poor countries
Spread face-oral - often by water contamination
Cause dysenteriae

Question 15

What is salmonella?

Answer 15

Gram -ve
Spread from food - mainly chicken and dairy
Lab detection- MacConkey - non-lactose fermenting - stays yellow

Question 16

What is s. typhi

Answer 16

Gram -ve strain of salmonella

Cause typhoid fever - initiate in intestine can spread systemically

Question 17

What are campylobacter spp?

Answer 17

Gram -ve microaerophiles
No 1 cause of food poisoning (c. jejui most common)
Last up to 3 weeks
Complication: reactive arthritis and guiilame barre

Question 18

What are cholera spp?

Answer 18

Caused gram -ve comma shaped bacterium
Infectious dose = large
Characterised - rice water stool
No tissue damage

Question 19

How does cholera toxin work?

Answer 19

G-protein signalling pathway - increase secretion Cl- ion - prevent influx Na+ into cells
Result water movement into lumen and diarrhoea

Question 20

Tx cholera?

Answer 20

Rapid fluid and electrolyte replacement

Prevention - improvement water system and sanitation

Question 21

Name some viral cause GI infections?

Answer 21

Rotavirus

Noravirus

Question 22

What is a rotavirus

Answer 22

Wheel like viral particle - cause damage small intestine - diarrhoea
Low infectious dose - very contagious

Question 23

What is noravirus?

Answer 23

Winter vomiting virus
Chills, headache, fever, nausea
Low infectious dose