GI Infections

Question 1

Anaerobic GI organism

Answer 1

Clostridia

Question 2

Canned/vacuum packed foods: Honey (kids), beans (students). Ingestion of preformed toxin (inactivated by cooking)
Blocks Ach release from peripheral nerves - descending paralysis (different from GBS)

Answer 2

Clostridia Botulinum

Tx - antitoxin

Question 3

Reheated meats, superantigen enterotoxin (bind directly to TCR + MHC outside peptide binding site - massive cytokine production by CD4 ie systemic toxicity
+ supression of adaptive response
Acts on small bowel 8-16 hours incubation
Watery diarrhoea + cramps, lasts 24 hours
Causes gas gangrene

Answer 3

Clostridia Perfringens

Question 4

2 exotoxins (A,B)
Get pseudomembranous colitis (ie an inflamed bowel)
Caused by Abx usually cephalosporins/fluorquinolones

Answer 4

C Difficile
Tx - Metronidazole
Vancomycin PO

Question 5

Aerobic GI oraganisms

Answer 5

Bacillus Cereus

Staph Aureus

Question 6

Reheated rice (spores germinate) and sudden vomiting
Super antigen - short incubation (4hrs) increased cAMP - L:ong incubation 18 hrs
Watery non-bloody diarrhoea

Answer 6

Bacillus Cereus

Self limiting

Question 7

Main virulence factor Protein A
Catalase, coagulase +ve
Appears in tetrads - clusters on gram stain
Beta hemolytic on blood agar
Produces enterotoxin (exotoxin that acts as superantigen, releasing IL1 and 2 - prominent vomiting and watery non-bloody diarrhoea

Answer 7

Staph Aureus
Don’t treat
Self limiting

Question 8

Gram -ve lactose fermentor

Answer 8

Enterobacteriacae Coli

Question 9

Toxigenic, Travellers Diarrhoea
Heat labile LT stimulates adenyl cyclase and cAMP
Heat stable ST stimulates guanylate cyclase
Act on the jejeunum, ileum not on colon

Answer 9

Enterotoxigenic E Coli

ETEC

Question 10

Invasive Dysentery

Answer 10

Enteroinvasive E Coli

EIEC

Question 11

Haemorrhagic, caused by verotoxin

Answer 11

Enterohaemorrhagic E Coli

EHEC

Question 12

Anaemia, thrombocytopaenia, renal failure (0157:H7 toxin)

Answer 12

Haemolytic Uraemic Syndrome

HUS

Question 13

Infantile Diarrhoea (Paeds)

Answer 13

Enteropathogenic E Coli

EPEC

Question 14

Tx for E Coli

Answer 14

Self limiting
Can treat with cipro (avoid Abx)
Source - human faeces - contaminated food/water

Question 15

Non-lactose fermentors

Answer 15

Salmonella, Shigella, Yersinia enterocolitis

Question 16

Only transmitted by humans
Multplies in peyers patches
3% carriers in gallbladder
Slow onset fever + constipation
Relative bradycardia
SPlenomegaly and rose spots, anaemia and leukopenia

Answer 16

Salmonella typhi/paratyphi (enteric fever)

Tx Ceftriaxone or Ciprofloxacin

Question 17

Poultry, eggs and meat, invasion of small and large bowel Bacteraemia is infrequent
Self limiting non-bloody diarrhoea

Answer 17

Salmonella Enteritides

Tx Ceftriaxone or Ciprofloxacin (if required)

Question 18

Salmonella

Answer 18

O, H, Vi antigens, H2S producers, TSI agar, XLD agar, Selenite F broth

Question 19

Mainly affects distal ileum + colon -> mucosal inflammation, fever, pain, bloody diarrhoea,. Shiga enterotoxin

Answer 19

Shigella
Avoid Abx (Cipro if required)

Question 20

Enterocolitis, mesenteric adenitis w/ necrotising granulomas, associated reactive arthritis and erythema nodosum
Transmitted via food contaminated with domestic animals excreta
Prefers 4 degress cold enrichment

Answer 20

Yersinia

Question 21

COmma shaped
Late lactose fermentors
Oxidase +ve

Answer 21

Vibriosis

comma shaped

Question 22

Rice water stool
Human faeces (in shellfish)
Increase cAMP opens Cl channel at apical membrane of enterocytes - efflux of CL to lumen (loss of H2O and electrolytes)
Massive diarrhoea without inflammation

Answer 22

Vibrio Cholera

Tx Supportive

Question 23

Ingestion of raw undercooked seafood (common in japan)

3/7 of diarrhoea often self-limiting

Answer 23

Vibrio Parahaemolyticus

Tx Doxycycline

Question 24

Cellulitis in shellfish handlers

Fatal septicaemia with D+V in HIV patients

Answer 24

Vibrio Vulnificus

Tx Doxycycline

Question 25

Curved, comma or S shaped Misc Gi organism

Answer 25

Campylobacter

Question 26

Drinking unpasteurised milk, food eg poultry Prodrome of headache and fever, abdo cramps, bloody foul-smelling diarhhoea Curved, S-shaped, microaerophillic, oxidase +ve, motile, sensitive to malidixic acid (first quinolone) ASsoc with Guillain-Barre and reactive arthritis

Answer 26

Campylobacter Jejuni | Erythromycin or Cipro if first 4-5 days

Question 27

V or L shaped protozoa Beta Haemolytic Aesculin +ve Tumbling motility

Answer 27

Listeria Monocytogenes

Question 28

GI Watery diarrhoea, cramps, headache, fever, little vomiting Perinatal infection, immunocompromised patients Outbreaks of febrile gastroenteritis Refrigerated food - unpasteurised dairy, vegetables

Answer 28

Listeria monocytogenes | Tx - Ampicilliin, Ceftriaxone, Cotrimoxazole

Question 29

Motile trophozoite in diarrhoea Non-motile cyst in non-diarrhoea 4 nuclei and no animal reservoir. Colonise colon Makes flask shaped ulcer (histology) Sx: Dysentery, wind, tenesmus, Chronic weight loss and RUQ pain (liver abscess)

Answer 29

``` Entamoeba Histolytica Associated with MSM ALso food, water, soil Stool Microscopy Tx - Metronidazole + Paromomycin if luminal ```

Question 30

Pear shaped trophozoite 2 nuclei trophozoites/cysts found in stool Get it by ingesting cysts from faecally contaminated H2P Malabsorption of protein and fat - foul semlling non-bloody diarrhoea

Answer 30

Giardia Lamblia EMQ: Travellers/Hikers/MSM/Mental hospitals Dx: ELISA string test Tx: Metronidazole

Question 31

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

Answer 31

Cryptosporidium Parvum | Tx: Paromomycin, Nitazoxanide in kids

Question 32

Mycobacterium - M Tb, MAI

Answer 32

Always a possibility | Assoc with HIV

Question 33

Viruses that cause GI problems

Answer 33

Rotavirus

Question 34

No/Low grade fever | No white blood cells in stool

Answer 34

``` Secretory Diarrhoea V Cholera ETEC EAggEC EPEC EHEC ```

Question 35

Fever | White blood cells in stool (Neutrophils)

Answer 35

``` Inflammatory DIarrhoea Camylobacter jejuni Shigella spp Non-typhoidal Salmonella serotypes EIEC ```

Question 36

Fever | White blood cells in stool (Mononuclear cells)

Answer 36

Enteric Fever Typhoidal salmonella Enteropathogenic Yersinia Spp Brucella spp