GI Infection

Question 1

What is the epidemiology of GI infections?

Answer 1

Underreporting of GI infections

Most are self limiting <24 hours, patients do not seek healthcare

Developing countries-outbreaks, cholera especially in war torn countries with no access to clean drinking water and sanitation

Most vulnerable groups: Infants, elderly

Reportable: Campylobacter, Salmonella, Shigella, E.Coli 0157, Listeria, Norovirus

Question 2

What is the difference between secretory diarrhoea, inflammatory diarrhoea and enteric fever?

Answer 2

Question 3

What is the incubation, duration and cause of campylobacter?

Answer 3

1-10 days

2-20

Poultry

Question 4

What is the incubation, duration and cause of EColi 0157?

Answer 4

1-5 days

1-4

HUS, verotoxin

Question 5

What is the incubation, duration and cause of Shigella?

Answer 5

12-96hrs

5-7

Small infective dose, outbreaks

Question 6

What is the incubation, duration and cause of Salmonella (non typhoid)?

Answer 6

8-48h

4-7

Rare cause systemic dx

Question 7

What is the incubation, duration and cause of vibro prahaemolyticus?

Answer 7

24-72h

2-10

Shellfish

Question 8

What is the incubation, duration and cause of vibrio cholera?

Answer 8

1-5 days

Variable

Ricewater, endemic

Question 9

What is the incubation, duration and cause of Bacillus Cereus?

Answer 9

1-6h

<1 day

Heat stable emetic toxin (rice)

Question 10

What is the incubation, duration and cause of Staph Aureus?

Answer 10

2-7h

<1day

Preformed toxin

Question 11

How do secretory toxins work?

Answer 11

cAMP: opens Cl channel at the apical membrane of enterocytes

>> efflux of Cl to lumen; loss of H2O and electrolytes

Question 12

How do superantigens work?

Answer 12

Superantigens bind directly to

T-cell receptors and

MHC molecules;

outside the peptide binding site

>> massive cytokine production by CD4 cells ie systemic toxicity and suppression of adaptive response

Question 13

What is the difference between inflammatory diarrhoea and enteric fever?

Answer 13

Host responses in bacteraemia:

Inflammatory (exudative ) diarrhoea

Vs

Enteric fever; interstitial inflammation

Question 14

What is Staph Aureus?

Answer 14

Food Poisoning

• 1/3 population chronic carriers, 1/3 transient
• Spread by skin lesions on food handlers
• Catalase, coagulase positive Gram positive coccus
• Appears in tetrads, clusters on Gram stain
• Yellow colonies on blood agar

Question 15

How dose S Aureus work?

Answer 15

Produces enterotoxin, an exotoxin that can act as a superantigen in the GI tract, releasing IL1 and IL2

…causing prominent vomiting and watery, non bloody diarrhoea

Don’t treat, self limited

Question 16

What does Bacillus cereus do?

Answer 16

•Bacillus cereus : food poisoning

Spores germinate in reheated fried rice

Gram positive rods: spore forming

Question 17

What is Bacillus Cereus?

Answer 17

• Gram positive rod-spores
• Heat stable emetic toxin

-not destroyed by reheating

• Heat labile diarrhoeal toxin
• -food is not cooked to a high enough temperature

and

• watery non bloody diarrhoea; self limited
• Rare cause of bacteremia in vulnerable population
• Can cause cerebral abscesses

Question 18

What is clostridia botulinum?

Answer 18

• Source : canned or vacuum packed food (honey / infants)
• Ingestion of preformed toxin (inactivated by cooking)
• Blocks Ach release from peripheral nerve synapses
• Treatment with antitoxin

Question 19

What is clostridium pefringens?

Answer 19

• Source : reheated food (meat)
• Normal flora of colon but not small bowel, where the enterotoxin acts (superantigen)
• Incubation 8-16hrs
• Watery diarrhoea, cramps,little vomiting lasting 24hrs

Question 20

Why is pseudomembranous colitis bad?

Answer 20

• 3%, 30% of hospitalised patients
• Antibiotic related colitis (any but.. mainly cephalosporins, cipro and clindamycin)

Question 21

How do you manage C diff?

Answer 21

• Infection control
• Treatment : (PO) metronidazole, vancomycin, stop antibiotics where possible

Question 22

What is Listeria monocytogenes?

Answer 22

• Outbreaks of febrile gastroenteritis
• ß haemolytic, aesculin positive with tumbling motility
• Source : refrigerated food (“cold enhancement”),i.e. unpasteurised dairy, vegetables
• Grows at 4 ºC GI watery diarrhoea, cramps, headache, fever, little vomiting
• Perinatal infection, immunocompromised patients
• Treatment : ampicillin

Question 23

What is enterobacteriacae?

Answer 23

Facultative anaerobes, glucose/lactose fermenters (LF),

oxidase negative

Question 24

What is E coli?

Answer 24

• Traveller’s diarrhoea
• Source: food/water contaminated with human faeces
• Enterotoxins :
• Heat labile stimulates adenyl cyclase and cAMP
• Heat stable stimulates guanylate cyclase
• Act on the jejeunum, ileum not on colon

Question 25

What are the types of E coli?

Answer 25

* ETEC; toxigenic, main cause of traveller’s diarrhoea * EPEC; pathogenic, infantile diarrhoea * EIEC; invasive, dysentery * EHEC; haemorrhagic O157:H7 EHEC: shiga- like verocytotoxin causes HUS * Avoid antibiotics

Question 26

What is salmonellae?

Answer 26

* Non lactose fermenters, * H2S producers, * TSI agar, * XLD agar,selenite F broth * Antigens: - cell wall O (groups A-I) - flagellar H - capsular Vi (virulence, antiphagocytic) •Three species : - S. typhi (and paratyphi) -S.enteritidis - S.cholerasuis

Question 27

What is S enteritidis?

Answer 27

Enterocolitis * transmitted from poultry, eggs, meat * invasion of epi- and sub-epithelial, tissue of small and large bowel * bacteraemia infrequent * self limited non bloody diarrhoea ,usually no treatment * Stool positivity

Question 28

What is S typhi?

Answer 28

Typhoid (enteric) fever * transmitted only by humans * multiplies in Payer’s patches, * spreads ERS * bacteraemia, 3% carriers * Slow onset, fever and constipation, * splenomegaly,rose spots, * anaemia, leucopaenia, * bradycardia, haemorrhage and * perforation * Blood culture positive * Treatment : ceftriaxone

Question 29

What is Shigellae?

Answer 29

* Non lactose fermenters, non H2S producers, non motile * Antigens: - cell wall O antigens, - polysaccharide (groups A-D) : S.sonnei, S.dysenteriae, S.flexneri (MSM) * The most effective enteric pathogen (low ID 50) * No animal reservoir * No carrier state * Dysentery - invading cells of mucosa of distal ileum and colon - producing enterotoxin (Shiga toxin) Avoid antibiotics (ciprofloxacin if required)

Question 30

What are Vibrios?

Answer 30

Curved, comma shaped, late lactose fermenters, oxidase positive.

Question 31

What is Vibrio Cholerae?

Answer 31

* O1 group: epidemics, biotypes El Tor, Cholerae and serotypes Ogawa, Inaba, Hikojima * Non O1 group: sporadic or non pathogens * Transmitted by contamination of water and food from human faeces ( shellfish, oysters, shrimp) * Colonisation of small bowel and secretion of enterotoxin with A and B subunit, causing persistent stimulation of adenylate cyclase * Causes massive diarrhoea (rice water stool) without inflammatory cells * Treat the losses

Question 32

What is Vibrioe parahaemolyticus?

Answer 32

- Ingestion of raw or undercooked seafood (ie oysters), - major cause of diarrhoea in Japan..or when cruising in the Carribean.. , - self limited for 3 days - cholerae : grows in salty 8.5% NaCl.

Question 33

What is Vibrio vulnificus?

Answer 33

- cellulitis in shellfish handlers - fatal septicaemia with D+V in HIV patients

Question 34

How do you treat vibrios diarrhoea?

Answer 34

Doxycycline

Question 35

What is campylobacter?

Answer 35

* Curved, comma or S shaped * Microaerophilic * C.jejuni at 42 ºC * oxidase pos ,motile * Self limiting but symptoms can last for weeks (20 days) * Only treat if immunocompromised (macrolide)

Question 36

Why is campylobacter bad?

Answer 36

* Transmitted via contaminated food and water with animal faeces ( poultry, meat,unpast. milk) * ? Enterotoxin (watery diarrhoea) ? Invasion (+/- blood) * Watery, foul smelling diarrhoea, bloody stool, fever and severe abdo pain * Treat with erythromycin or cipro if in the first 4-5days GBS syndrome, reactive arthritis, Reiter’s

Question 37

What is Yersinia enterocolitica?

Answer 37

- Non lactose fermenter, prefers 4ºC “cold enrichment” - Transmitted via food contaminated with domestic animals excreta - enterocolitis - mesenteric adenitis - associated with reactive arthritis , Reiter’s

Question 38

What is mycobacteria?

Answer 38

- will appear as Gram variable - always think of TB

Question 39

What is entamoeba histolytica?

Answer 39

* motile trophozoite in diarrhoea * non motile cyst in nondiarrhoeal illness * Killed by boiling, removed by water filters * 4 nuclei * No animal reservoir

Question 40

What are the clinical features of entamoeba histolytica?

Answer 40

Ingestion of cysts \>\> trophos in ileum \>\> colonize cecum, colon \>\> “flask shaped” ulcer -dysentery,flatulence, tenesmus - chronic : wt loss,+/- diarrhoea - liver abscess

Question 41

How do you diagnose entamoeba histolytica?

Answer 41

-stool micro (wet mount, iodine and trichrome ) -serology in invasive disease Treat : metronidazole + paromomycin in luminal disease

Question 42

What is Giardia lamblia?

Answer 42

* trophozoite “pear shaped” * 2 nuclei * 4 flagellas and a suction disk * Ingestion of cyst from fecally contaminated water,food * Excystation at duodenum * tropho attaches * no invasion * malabsorption of protein and fat

Question 43

Who gets giardia and how do we manage it?

Answer 43

•Travellers, hikers, day care, mental hospitals, MSM •foul smelling non bloody diarrhoea, cramps flatulence, no fever * Diagnosis : stool micro, ELISA, “string test” * Treatment :metronidazole

Question 44

What is Cryptosporidium parvum and how is it managed?

Answer 44

* Infects the jejunum * Severe diarrhoea in the immunocomromised * Oocysts seen in stool by modified Kinyoun acid fast stain Treatment : reconstitution of immune system

Question 45

What is Norovirus?

Answer 45

* outbreaks * Low ID (18-1000 viral particles) * Environmental resilience (0-60 ºC) * No long term immunity * GII.4 currently predominant strain

Question 46

What is rotavirus?

Answer 46

* dsRNA “wheel like” * Replicates in mucosa of small intestine * Secretory diarrhoea, no inflammation * Watery diarrhoea ? by stimulation of enteric nervous system * By age 6 most children worldwide have antibodies to at least one type * Exposure to natural infection twice confers lifelong immunity * Huge economic burden worldwide

Question 47

What is adenovirus?

Answer 47

Types 40, 41 cause non bloody diarrhoea \<2yrs of age Any type in immunocompromised

Question 48

What are the other viruses?

Answer 48

* Poliovirus * Enteroviruses (coxsackie, ECHO) * Hepatitis A transmitted via faecal-oral route but main presentations from other systems

Question 49

What is this?

Answer 49

Small bowel in viral GI infection

Question 50

What are Targets for promotion?

Answer 50

–Breastfeeding, improved weaning practice –Clean water for drinking –Safe disposal of stools of young children –Precautions when travelling –Food handling –Public health notification –Good handwashing –Good handwashing –Good handwashing

Question 51

Which vaccines exist?

Answer 51

•Cholera : serogroups O1(Inaba , Ogawa, biotypes El Tor and classical), O139 a. Inactivated, whole cell, contains all above + B subunit of toxin (PO) b. Live attenuated (PO) not recommended * Campylobacter : military, infants,traveller, candidate vaccines exist.. * ETEC : inactivated and live vaccines in trials * Salmonella typhi : Vi capsular PS (IM) and (PO)live

Question 52

What is the rotavirus vaccine?

Answer 52

* Rotarix : live attenuated human strain monovalent, 2(PO) doses * Rotateq : pentavalent, 3 (PO) doses, one bovine and four human strains * Rotashield and intussusception (8-20 weeks) * Age of vaccine is 6-12 weeks

Question 53

When does public health get involved?

Answer 53

* Notifiable disease * Each trust to notify to local Health Protection Unit * Campylobacter, Clostridium sp, Listeria monocytogenes, Vibrio, Yersinia * Identify outbreaks in areas * Environmental Health Officers to inspect premises and take samples from environment and food

Question 54

What is gastroenteritis?

Answer 54

Rapid onset diarrhoeal illness lasting less than 2 weeks and has to be loose and 3+ times a day.

Question 55

What are the risk factors of GI infections?

Answer 55

Foodborne Expsoure related Host related

Question 56

What is Diarrhoea?

Answer 56

Loose or watery stools passed at least 3 times in 24 hours which can be acute (\<14 days), persistent (14-29 days) or chroni (\>30d).

Question 57

What's the difference between small bowel and large bowel diarrhoea?

Answer 57

Small bowel = watery, crampy pain, large volume, bloating, gas. Less likely to have fever/ blood/ inflammatory cells in the stool. Large bowel = small volume, painful stool with blood, mucus, inflammatory cells and fever.

Question 58

What condition can salmonella cause?

Answer 58

Aortitis