Gastroenteritis

Question 1

What are the features of clostridium botulinum and what is the treatment

Answer 1

Gram +ve anaerobe
Canned/vacuum packed foods: Honey (kids),
beans (students)
Ingestion of preformed toxin (inactivated by cooking)
Blocks Ach release from peripheral nerves →
Descending paralysis (differentiates from GBS)

Tx: antitoxin

Question 1

What are the features of Clostridium perfringens infection

Answer 1

Gram +ve anaerobe
Normal flora of the colon, but not the small bowel where the enterotoxin acts
Reheated meats, 8-16hrs incubation
Watery diarrhoea + cramps, lasts 24hrs
Also causes gas-gangrene

Question 2

What are the features of Clostridium difficile infection and what is the treatment

Answer 2

Gram +ve anaerobe
2 exotoxins (A,B)
- Toxin A = enterotoxin = inflammation
- Toxin B = cytotoxin = virulence factor (more dangerous)
Pseudomembranous colitis
Suspect if severe diarrhoea + recent Hx of Abx (usually cephalosporins/fluorquinolones)

Tx: metronidazole, 2nd line vancomycin

Question 3

What are the features of bacillus cereus infection

Answer 3

Gram positive rods, spore-forming
Reheated rice (spore germinates)– suspect after re-heated takeout
Short incubation ~4hrs
Sudden vomiting and watery, non-bloody diarrhoea
Superantigen — short incubation (4hrs)
Increased cAMP— long incubation (18hrs)
Self-limiting
May cause cerebral abscess

Question 4

What are the features of staph aureus infection

Answer 4

Gram +ve clusters of cocci on gram stain, catalase, coagulase +ve, yellow colonies on blood agar
Spread by skin lesions on food handlers
Produces enterotoxin (acts as superantigen → IL1/2
release)
Short incubation ~2hrs
Prominent vomiting, watery non-bloody diarrhoea
Self-limiting

Question 5

What are the features of E. Coli infection and how is it treated

Answer 5

Gram negative rod (Facultative anaerobes, glucose/lactose fermenters (LF), oxidase-negative)
Transmitted in faeces/contaminated water
ETEC: toxigenic, traveller’s diarrhoea
EIEC: invasive dysentery
EHEC: Haemorrhagic → HUS
HUS: Anaemia, thrombocytopenia, renal failure (0157:H7 toxin)
EPEC: Infantile diarrhoea (Paeds)

Tx: self-limiting, can treat with cipro

Question 6

What are the features of typhoidal salmonella infection and how is it treated

Answer 6

Typhi + paratyphi
Multiplies in Peyer’s patches, spreads ERS
Enteric fever: Constipation, fever, rose spots,
splenomegaly

Tx: IV ceftriaxone → PO azithromycin

Question 7

What are the features of non-typhoidal salmonella infection and how is it treated

Answer 7

Enteritides
Poultry, eggs, meat
Non-bloody diarrhoea, no fever

Tx: self-limiting, Ceftriaxone if required

Question 8

What are the features of shigella infection and how is it treated

Answer 8

No animal reservoir (human → human transmission)
Affects the distal ileum + colon → mucosal inflammation, fever, pain, bloody diarrhoea (dysentery)

Tx: self-limiting, cipro if required

Question 9

What are the features of vibrio infection

Answer 9

Cholera: Faeco-oral transmission (shellfish, oysters, shrimp). Rice water stool (massive diarrhoea without inflammation)
- Enterotoxin A and B subunit → persistent stimulation of adenylate cyclase

Parahaemolyticus: raw seafood (common in Japan)

Vulnificus: cellulitis in shellfish handlers

All self-limiting, treat dehydration, consider doxicyclin for para + vulni

Question 10

What are the features of campylobacter jejuni infection and how is it treated

Answer 10

Undercooked poultry (chicken at a BBQ)
Prodrome of fever and headache, then abdo cramps and bloody diarrhoea
Lasts ~10d
Associated with GBS, reactive arthritis, Reiter’s

Tx: erythromycin or cipro in first 5 days

Question 11

What are the features of listeria monocytogenes infection and how is it treated

Answer 11

Refrigerated food, unpasteurised dairy
Perinatal infection
Severe infection in immunocompromise
Water diarrhoea, cramps, headaches, fever

Tx: Ampicillin

Question 12

What are the features of entaemoeba histolytica infection and how is it treated

Answer 12

Motile trophozoite in diarrhoea; Non-motile cyst in non-diarrhoeal illness
Flask-shaped ulcer on histology with 4 nuclei
Dysentery, flatulence, tenesmus
More common in MSM

Tx: metronidazole

Question 13

What are the features of giardia lamblia infection and how is it treated

Answer 13

Pear-shaped trophozoite with 2 nuclei, 4 flagella and suction disc
Causes malabsorption of fat → foul-smelling non-bloody diarrhoea

Tx: metronidazole

Question 14

What are the features of cryptosporidium parvum infection and how is it treated

Answer 14

Severe diarrhoea in immunocompromised
Infects jejunum
Oocysts seen in stool by modified Kinyoun acid fast stain

Tx: paromomycin

Question 15

What are the features of viral causes of GI infection

Answer 15

Norovirus: secretory diarrhoea in adult outbreaks, no long-term immunity, low ID load with environmental resilience
Adenovirus: secretory diarrhoea <2yo
Rotavirus: secretory diarrhoea <6yo, dsRNA “wheel like”, exposure 2x → lifelong immunity

All self-limiting

Question 16

Define gastroenteritis

Answer 16

rapid onset diarrhoeal illness, lasting <2 weeks with diarrhoea (loose or unformed stool) ≥3/day or ≥200g of stool which is either viral or bacterial in aetiology

Question 17

Define diarrhoea

Answer 17

loose or watery stool, ≥3 times in 24 hours

Question 17

What defines acute, persistent, and chronic diarrhoea

Answer 17

Acute <14 days (may be viral or bacterial)
Persistent 14-29 days
Chronic >30 days (may be due to parasites and non-infectious aetiology)

Question 18

What are the differences between small and large bowel diarrhoea

Answer 18

Small bowel diarrhoea = watery, crampy abdominal pain, bloating and gas; inflammatory cells rare

Large bowel diarrhoea = small volume, painful, occur with blood/mucous; inflammatory cells common

Question 19

What investigations should be done for GI infections

Answer 19

Stool culture and sensitivity + for ova and parasites

U&Es
Glucose
Blood cultures

Question 20

Which causes of gastroenteritis are notifiable disease

Answer 20

Food poisoning: suspected
- Bacillus cereus
- Campylobacter spp.
- Clostridium perfringens
- Cryptosporidium spp.
- Entamoeba histolytica
- verocytotoxigenic Escherichia coli [including E. coli O157:H7]
- Salmonella spp.
- Giardia lamblia
- Yersinia pestis)
Haemolytic uraemic syndrome.
Infectious bloody diarrhoea, such as Shigella spp.
Enteric fever (typhoid or paratyphoid fever).
Cholera

Question 21

What necessitates hospital admission in gastroenteritis

Answer 21

Systemically unwell and/or there are clinical features suggesting severe dehydration and/or progression to shock
There is intractable or bilious vomiting or high-output diarrhoea
Acute-onset painful, bloody diarrhoea
Confirmed STEC infection O157
Suspected serious complication e.g. HUS, sepsis
Inadequate response to ORS

Question 22

Management for gastroenteritis:

Answer 22

Advice:
- Patient.info leaflets / NHS lefalets
- Regular fluid intake + fruit juice supplements
- Small, light, non-fatty, non-spicy meals may be better tolerated
- Prevent transmission: wash hands, always flush, clean bathroom at least once daily, do not share towels, washed all soiled clothing/linen separately
- EXCLUSION for at least 48 hours after the last episode of diarrhoea or vomiting

Medical
- Oral rehydration salt (ORS) solution
- 200-400mL after every loose motion
Given if: At an increased risk of dehydration e.g. elderly, immunocompromised, co-morbid conditions or concurrent illness OR Clinical features of dehydration but do not require admission

Mild-moderate diarrhoea → antidiarrhoeal drugs (NOT for bloody diarrhoea)

+ notify local health protection team