GI infections

Question 1

Clostridium botulinum

Answer 1

Canned/vacuum food (honey for kids, beans for students).
Ingest preformed toxin. Inactivated by cooking.
Blocks ACh release, so paralysis, descending (cf GBS).
Tx: antitoxin.

Question 2

Clostridium perfringens

Answer 2

Reheated meats, superAg enterotoxin.
8-16 hours incubation.
Acts on small bowel. Watery diarrhoea, cramps, 24 hours.

Question 3

Clostridium difficile

Answer 3

Caused by Abx (cephalosporins/fluoroquinalones (-floxacin)).
Exotoxins A and B. Pseudomembranous colitis.
Metronidazole, or vancomycin if bad.

Question 4

Bacillius cereus

Answer 4

Reheated rice (spores). 
SuperAg, ^cAMP. 
4 hours incubation. 
Sudden vomiting. Watery diarrhoea. 
Self-limiting.

Question 5

Staph. aureus

Answer 5

G+. Catalase +, coagulase +. Tetrads. Beta-haemolytic.
Protein A stops IgG. Enterotoxin (superAg, IL1 IL2):
Prominent vomiting, water diarrhoea.
Self-limiting.

Question 6

E coli

Answer 6

From human faeces.
G- enterobacter.
Facultative anaerobes, ferment lactose, oxidase -.
Self-limiting, but can give ciprofloxacin if dire.

Question 7

ETEC

Answer 7

Toxigenic / Traveller’s E coli.
Heat labile toxin LT stimulates adenyl cyclase ^cAMP;
ST stimulates guanylate cylase ^cGMP. (stable Ground)
Jejunum and ileum.

Question 8

EIEC

Answer 8

Invasive dysentery E coli.

Question 9

EHEC

Answer 9

Haemorrhagic E coli, so bloody diarrhoea. Verotoxin.

Question 10

EPEC

Answer 10

Paediatric E coli: infantile diarrhoea.

Question 11

HUS

Answer 11

Anaemia, thrombocytopaenia, renal failure,

due to E coli 0157:H7 toxin.

Question 12

Salmonellae

Answer 12

?

Question 13

Salmonella typhi

Answer 13

Typhoid fever. 
Only transmitted by humans. 
Multiplies in Peyer's patches. 
Slow onset fever, *constipation*, spleen, rose spots, anaemia, leukopaenia. 
Ceftriaxone or ciprofloxacin.

Question 14

Salmonella enteridis

Answer 14

Poultry, eggs, meat.
Invades small and large bowel; rarely bacteraemia.
Diarrhoea.
Self-limiting.

Question 15

Shigella (dysenteriae)

Answer 15

Shiga enterotoxin,
Bloody diarrhoea
due to musocal inflam in distal ileum and colon.
Self-limiting.

Question 16

Yersinia enterocolitis

Answer 16

Domestic animal poo.
Enterocolitis, mesenteric adenitis, necrotising granulomata, reactive arthritis, erythema nodosum.
4oC “cold enrichment”.

Question 17

Vibrio cholerae

Answer 17

Human faeces, ? in shellfish.
cAMP opens Cl channel, lose Cl and water: massive diarrhoea without inflam.
Supportive Tx.

Question 18

Vibrio parahaemolyticus

Answer 18

Raw seafood (Japan).
3 days diarrhoea.
Self-limiting, or Doxycycline.

Question 19

Vibrio vulnificus

Answer 19

Shellfish - cellulitis in handlers.
In HIV: fatal septicaemia with D+V.
Doxycycline.

Question 20

Campylobacter jejuni

Answer 20

Unpasteurised milk, poultry.
Curved, motile, oxidase +.
Prodrome: headache and fever.
Bloody foul smelling diarrhoea, abdo cramps.
Assoc: Guillain-Barré, reactive arthritis (Reiter’s).
Erythromycin (or cipro if early). (Sensitive to nalidixic acid, first quinolone).

Question 21

Listeria monocytogenes

Answer 21

Refrigerated unpasteurised food.
L-shaped, beta-haemolytic, aesculin +, tumbling.
Sepsis / meningitis / diarrhoea, cramps, headache, fever.
Perinatal infection, immunocompromised.
Outbreaks of febrile gastroenteritis.
Ampicillin, ceftriaxone, cotrimoxazole.

Question 22

Entamoeba histiolytica

Answer 22

Ingestion of cysts (MSM).
Motile trophozoite (or in non-diarrhoeal, non-motile cyst). nuclei.
Flask-shaped ulcers. Colonise colon.
Dysentery (blood, tenesmus), weight loss, RUQ pain (liver abscess).
Metronidazole + paramomycin.

Question 23

Giardia lamblia

Answer 23

Ingest cysts from water. Travellers/MSM/mentals.
Pear-shaped trophozoites.
Malabsorption of protein and fat, so foul smelling diarrhoea.
Dx: ELISA string test.
Metronidazole.

Question 24

Cryptosporidium parvum

Answer 24

Severe diarrhoea from infected jejunum in immunocompromised.
Oocysts in stool - modified Kinyoun acid fast stain.
Paramomycin.

Question 25

Viruses causing diarrhoea

Answer 25

Rotavirus: