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PathY5 > GI Infection > Flashcards

GI Infection Flashcards

1
Q

What is the epidemiology of GI infections?

A

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

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2
Q

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

A
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3
Q

What is the incubation, duration and cause of campylobacter?

A

1-10 days

2-20

Poultry

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4
Q

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

A

1-5 days

1-4

HUS, verotoxin

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5
Q

What is the incubation, duration and cause of Shigella?

A

12-96hrs

5-7

Small infective dose, outbreaks

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6
Q

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

A

8-48h

4-7

Rare cause systemic dx

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7
Q

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

A

24-72h

2-10

Shellfish

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8
Q

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

A

1-5 days

Variable

Ricewater, endemic

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9
Q

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

A

1-6h

<1 day

Heat stable emetic toxin (rice)

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10
Q

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

A

2-7h

<1day

Preformed toxin

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11
Q

How do secretory toxins work?

A

cAMP: opens Cl channel at the apical membrane of enterocytes

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

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12
Q

How do superantigens work?

A

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

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13
Q

What is the difference between inflammatory diarrhoea and enteric fever?

A

Host responses in bacteraemia:

Inflammatory (exudative ) diarrhoea

Vs

Enteric fever; interstitial inflammation

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14
Q

What is Staph Aureus?

A

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
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15
Q

How dose S Aureus work?

A

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

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16
Q

What does Bacillus cereus do?

A

•Bacillus cereus : food poisoning

Spores germinate in reheated fried rice

Gram positive rods: spore forming

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17
Q

What is Bacillus Cereus?

A
  • 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
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18
Q

What is clostridia botulinum?

A
  • 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
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19
Q

What is clostridium pefringens?

A
  • 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
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20
Q

Why is pseudomembranous colitis bad?

A
  • 3%, 30% of hospitalised patients
  • Antibiotic related colitis (any but.. mainly cephalosporins, cipro and clindamycin)
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21
Q

How do you manage C diff?

A
  • Infection control
  • Treatment : (PO) metronidazole, vancomycin, stop antibiotics where possible
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22
Q

What is Listeria monocytogenes?

A
  • 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
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23
Q

What is enterobacteriacae?

A

Facultative anaerobes, glucose/lactose fermenters (LF),

oxidase negative

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24
Q

What is E coli?

A
  • 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
25
Q

What are the types of E coli?

A
  • 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
26
Q

What is salmonellae?

A
  • 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
27
Q

What is S enteritidis?

A

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
28
Q

What is S typhi?

A

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
29
Q

What is Shigellae?

A
  • 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)

30
Q

What are Vibrios?

A

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

31
Q

What is Vibrio Cholerae?

A
  • 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
32
Q

What is Vibrioe parahaemolyticus?

A
  • 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.
33
Q

What is Vibrio vulnificus?

A
  • cellulitis in shellfish handlers
  • fatal septicaemia with D+V in HIV patients
34
Q

How do you treat vibrios diarrhoea?

A

Doxycycline

35
Q

What is campylobacter?

A
  • 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)
36
Q

Why is campylobacter bad?

A
  • 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

37
Q

What is Yersinia enterocolitica?

A
  • Non lactose fermenter, prefers 4ºC “cold enrichment”
  • Transmitted via food contaminated with domestic animals excreta
  • enterocolitis
  • mesenteric adenitis
  • associated with reactive arthritis , Reiter’s
38
Q

What is mycobacteria?

A
  • will appear as Gram variable
  • always think of TB
39
Q

What is entamoeba histolytica?

A
  • motile trophozoite in diarrhoea
  • non motile cyst in nondiarrhoeal illness
  • Killed by boiling, removed by water filters
  • 4 nuclei
  • No animal reservoir
40
Q

What are the clinical features of entamoeba histolytica?

A

Ingestion of cysts >> trophos in

ileum >> colonize cecum, colon >> “flask shaped” ulcer

-dysentery,flatulence,

tenesmus

  • chronic : wt loss,+/- diarrhoea
  • liver abscess
41
Q

How do you diagnose entamoeba histolytica?

A

-stool micro (wet

mount, iodine and trichrome )

-serology in invasive disease

Treat : metronidazole + paromomycin in luminal disease

42
Q

What is Giardia lamblia?

A
  • 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

43
Q

Who gets giardia and how do we manage it?

A

•Travellers, hikers,

day care, mental hospitals,

MSM

•foul smelling non

bloody diarrhoea, cramps

flatulence, no fever

  • Diagnosis : stool micro, ELISA, “string test”
  • Treatment :metronidazole
44
Q

What is Cryptosporidium parvum and how is it managed?

A
  • Infects the jejunum
  • Severe diarrhoea in the immunocomromised
  • Oocysts seen in stool by

modified Kinyoun acid fast stain

Treatment : reconstitution of immune system

45
Q

What is Norovirus?

A
  • outbreaks
  • Low ID (18-1000 viral particles)
  • Environmental resilience (0-60 ºC)
  • No long term immunity
  • GII.4 currently predominant strain
46
Q

What is rotavirus?

A
  • 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
47
Q

What is adenovirus?

A

Types 40, 41 cause non bloody diarrhoea <2yrs of age

Any type in immunocompromised

48
Q

What are the other viruses?

A
  • Poliovirus
  • Enteroviruses (coxsackie, ECHO)
  • Hepatitis A

transmitted via faecal-oral route but main presentations from other systems

49
Q

What is this?

A

Small bowel in viral GI infection

50
Q

What are Targets for promotion?

A

–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

51
Q

Which vaccines exist?

A

•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
52
Q

What is the rotavirus vaccine?

A
  • 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
53
Q

When does public health get involved?

A
  • 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
54
Q

What is gastroenteritis?

A

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

55
Q

What are the risk factors of GI infections?

A

Foodborne

Expsoure related

Host related

56
Q

What is Diarrhoea?

A

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).

57
Q

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

A

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.

58
Q

What condition can salmonella cause?

A

Aortitis

PathY5 (98 decks)

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