Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

PATH FINAL > Micro: GI Infections > Flashcards

Micro: GI Infections Flashcards

1
Q

Epidemiology of GI infections

A
  • Vulnerable groups: infants and elderly
  • Most are self-limiting (hence do not seek medical care)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Reportable GI infections

A

Most gastroenteritis cases are reportable. However these are the most important to report:
* Camplybacter
* Salmonella
* Shigella
* Escherichia coli O157
* Listeria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

3 types of clinical syndromes associated with GI infections

A

Secretory diarrhoea
Inflammatory diarrhoea
Enteric fever

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How can you differentiate between the different GI infections clinical syndromes

A

If main symptoms are gastroenteritis (diarrhoea, GI cramps) then check if they have a a fever:
- no fever = secretory diarrhoea
- fever = inflammatory diarrhoea

If main symptom is fever and systemically unwell with fewer GI side effects = enteric fever

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Secretory diarrhoea:
- Pathophysiology
- Main symptoms
- Common causative pathogens

A

Pathophysiology
- Toxin production can either 1) induce cAMP in enterocytes which opens Cl- channels at apical membrane of enterocytes causing a Cl- efflux into lumen which results in watery diarrhoea and dehydration OR 2) toxin superantigen binds to T cell receptors causing massice cytokine release which causes Cl- secreted into lumen.

Symptoms
- Watery diarrhoea with NO fever
- no inflammatory cells in stool

Common causative pathogens
- Cholera
- Enterobacteriacae (ETEC, EPEC)
- Viruses (Norovirus, Adenovirus, Rotavirus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Inflammatory diarrhoea:
- Pathophysiology
- Main symptoms
- Common causative pathogens

A

Pathophysiology
- inflammation AND bacteraemia which in immunocompromised patients may result in shock

Symptoms
- Bloody diarrhoea (=dysentery) with inflammatory cells in stool
- Fever

Common causative pathogens
(CHESS)
- Campylobacter
- EHEC
- Entamoeba
- Salmonella (non-typhoidal)
- Shigella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Enteric diarrhoea:
- Main symptoms
- Common causative pathogens

A

Main Symptoms
- Systemically unwell
- Fever
- Fewer GI symptoms

Common Causative Pathogens
- Typhoidal salmonella
- Yersinia
- Brucella

these are more severe GI infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What type of organism is Staph. Aureus (4)

A

Gram positive cocci appearing in clusters
Catalase and coagulase positive
Aerobic
Yellow in agar plate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

GI infection: Staph. Aureus
How does Staph. Aureus cause a GI infection

A

Produces enterotoxin which acts as a superantigen causing IL1/2 release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

GI infection: Staph. Aureus
Incubation & Duration
How is it spread

A
  • VERY SHORT incubation of 2-4 hours
  • Duration of <1 day
  • Spread by skin lesions (commonly through infected food handlers)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

GI infection: Staph. Aureus
Symptoms and Treatment

A

Symptoms
Prominent vomiting
Watery non-bloody diarrhoea
type of secretory diarrhoea

Treatment
Self-limiting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What type of organism is Bacilus Cereus (3)

A

Gram positive rods
Aerobe
Spore forming

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

GI infection: B. Cereus
Source of infection
Incubation & Duration period

A

Source of infection
- Reheated rice (reheating causes to germinate)

Incubation & Duration
Incubation = 1-6 hours
Duration = <1 day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

GI infection: B. Cereus
Pathophysiology
Symptoms (and complications)
Treatment

A

Pathophysiology
- Produces toxins. Heat-stable emetic toxin (not destroyed upon reheating) and heat-labile diarrhoeal toxin(destroyed in reheating, but present in improper heating of food)

Symptoms
Vomiting and non-bloody watery diarrhoea
May cause bacteraemia and cerebral abscesses in vulnerable populations

Treatment
Self-limiting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What type of organism is Clostridium
What are the different types of Clostridium

A

Gram positive rod + anaerobe

Types
- Clostridium Botulinum
- Clostridium Perfringens
- Clostridium Difficile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

GI infections: Clostridium
Differentiate between the different types of Clostridium infections

A

Clostridium botulinum - causes botulism

  • From canned food and packed food (honey, beans)
  • Causes disease due to preformed toxin which cleaves SNARE proteins preventing acetylcholine release at peripheral nerve synapses resulting in descending paralysis (differentiate from GBS - ascending)
  • Treated with antitoxin

Clostridium perfringens - food poisoning

  • From reheated food (8-16hr incubation)
  • Generates a superantigen that mainly affects the colon
  • Causes watery diarrhoea and cramps that last 24 hours
  • Complication: gas gangrene

Clostridium difficile - pseudomembranous colitis

  • Hospital-acquired infection related to antibiotic use (4C’s: cephalosproins, Ciprofloxacin, Clindamycin, Co-Amoxiclav)
  • Has 2 exotoxins (A, B)
  • Treatment: 1) stop offending abx 1) Vancomycin (second line=fidaxomicin)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What type of organism is Listeria (3)

A

Gram positive rod
Beta-haemolytic, aesculin-positive
Motile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

GI infection: Listeria Monocytogenes
Source of infection

A

Refrigerated food (sandwich, veggies)
Unpasteurised dairy (monocyto-cheese!)
Often causing an outbreak of febrile gastroenteritis

19
Q

GI infection: Listeria Monocytogenes
Symptoms
Treatment

A

Symptoms
- Fever + watery diarrhoea
- Headache
- Little vomiting
- most vulnerable groups = perinatal infection (may result in stillbirth) and immunocompromised pts

Treatment
- Ampicillin

20
Q

What are the gram positive bacteria which may cause a GI infection

A

Staph A (cocci + clusters)
Bacillus Cereus (rods + aerobic + spore forming)
Clostridium (rods + anaerobic)
Listeria (rods + beta haemolytic + motile)

21
Q

What type of organisms are Enterobacteriaceae (4)

A
  • Gram negative
  • Faculative anaerobe (makes ATP if O2 present but can undergo fermentation in anaerobic environments)
  • Lactose fermenters
  • Oxidase-negatieve
22
Q

GI infection: E.Coli
Differentiate between the different types of infection

A

ETEC
- Toxigenic
- Main cause of travellers’ diarrhoea

EPEC
- Pathogenic
- Infantile diarrhoea

EIEC
- Invasive
- Dysentry

EHEC
- Haemorrhagic
- Caused by E. coli 0157:H7
- May result in haemolytic uraemic syndrome (due to shiga-like vierocytotoxin)
- Dysentery + MAHA + Renal failure
- Incubation of 1-5 days and duration 1-4 days

NOTE: ALL are spread through faecal-oral route

23
Q

GI infection: E.Coli
Treatment

A

Self-limiting
Avoid abx - thought to exacerbate condition

24
Q

What type of organisms are Salmonella (4)

A
  • Gram negatives
  • Non-lactose fermenting
  • Produce hydrogen sulphide (forming black colonies)
  • Motile
25
How can you differentiate the different types of *Salmonellae?*
Difference in antigens found on bacterium * Cell wall O (groups A-I) * Flagellar H * Capular Vi (virulence, antiphagocytic)
26
List two species of *Salmonella*.
* *Salmonella typhi (and paratyphi)* * *Salmonella enteritidis*
27
**GI infection: Salmonella Enteritidis and Typhi** Differentiate between the two types of Salmonella infection
**Salmonella Enteritidis** - invasion of epi and sub epithelial tissue of small and large bowel causing entercolitis - non-bloody diarrhoea (stool +ve cultures) - 12-48hr incubation period - No fever and bacteriaemia is rare - Transmitted by poultry, eggs, meat, reptile pets **Salmonella Typhi** - Transmitted only by humans - Multiples in Peyer's patches and spreads via endoretircular system (resulting in bacteraemia - +ve blood cultures) - Sx = Slow onset fever and constipation + splenomegaly + rose spots + anaemia + leucopaenia (fever in returning traveller!)
28
**GI infection: Salmonella Enteritidis and Typhi** Treatment
Salmonella Enteritidis = self-limiting Salmonella typhi = IV ceftriaxone then PO azithromycin
29
What type of organism is Shigella (4)
* Gram negative * Non-lactose fermenter * Does NOT produce hydrogen suphide * Non-motile
30
**GI infection: Shigella** Pathophysiology
* Produces shiga toxin affecting teh distal ileum and colon resulting in mucosal inflammation * Highly infectious (very small infective dose - lowest of GI infections!!!) hence behind many outbreaks Incubation of 12-96 hours with Duration of 5-7 days
31
**GI infection: Shigella** Symptoms Treatment
**Symptoms** - Dysentery (severe diarrhoea with blood and mucus) - Fever - Abdominal pain **Treatment** - Self-limiting - Try to avoid abx but Ciprofloxacin can be given if needed
32
What type of organism is Vibrio
Gram negative Comma-shaped Late lactose-fermenters Oxidase-positive
33
**GI infection: Vibrio Cholera** Pathophysiology
Colonisation of small bowel, where enterotoxin stimulates cAMP resulting in opening of Cl- channels and Cl- efflux out of cells. This results in Na+ moving out and water following by osmosis ==> severe dehydration! Transmitted by human faeces in contaminated water (especially in water borne food - rice, shellfish)
34
**GI infection: Vibrio Cholera** Symptoms and treatment
**Symptoms** Rice water stool - watery diarrhoea without inflammatory cells **Treatment** Self-limiting
35
**GI infection: Vibrio** Outliune the key features of other types of vibirio (excluding cholera)
***Vibrio parahaemolyticus:*** * Caused by ingestion of raw/undercooked seafood * Causes self-limiting diarrhoea * Grows on salty agar ***Vibrio vulnificus:*** * Causes cellulitis in shellfish handlers * Can cause fatal septicaemia with D&V in HIV patients, treated with doxycycline Both self-limiting
36
What type of organism is Campylobacter
* Gram negative s-shaped rod * Oxidase-positive * Grows at 42 degrees C * Motile
37
**GI infections: Campylobacter** Spread Symptoms
**Spread** Undercooked Poultry BBQ!!!! **Symptoms** * Prodrome of fever and headahce * Followed by abdominal cramps * Bloody diarrhoea * Lasts for 2-20 days
38
**GI infections: Campylobacter** Treatment Complications
**Treatment** - Erithromycin or Cirpo if in first 5 days - Otherwise after self-limiting - only treat if immunocompromised **Complications** - GBS - Reactive arthritis
39
**GI infections: Yersinia Enterocolitica** Key features
Sources: undercooked pork Symptoms - Fever, abdo pain, diarrhoea - (presentation may be like appendicitis) - Associated with reactive arthritis
40
What gram negative bacteria can cause GI infections
- **Enterobacteriaceae** (lactose fermenters, oxidase negative) - **Salmonella** (non-lactose, H2S producers, motile) - **Shigella** (non-lactose, non-H2S, non-motile) - **Vibrio** (comma-shaped, late lactose, oxidase positive) - **Campylobacter** (s-shaped/comma, lactose, oxidase, 42C, motile) - **Yersinia E.**
41
Protozoa which may cause GI infections & Key features
**Entamoeba Histolytica** - Flask-shaped ulcer in colon (seen on histology) - Sx: dystentery + flatulence + tenesmus - common in MSM - Dx: stool micro and serology - Complications: chronic infection may lead to liver abscess (RUQ pain, weightloss, fevers) - Rx: Metronidazole + Dantomyocin **Giardia Lamblia** - commonest protozoa GI infection - Pear-shaped trophozoite with 2 nuclei and 4 flagellae - Risk factors: travellers from South-East Asia - Spread from contaminated water + food - Sx: foul-smelling non-blood diarrhoea (as causes malabsorption of fat and protein) + lots of cramps + NO fevers - Dx: stool micro + ELISA - Rx: Metronidazole
42
Differentiate between viruses which may cause GI infections & Key features
**Norovirus** - GII.4 is the commonest strain - Adult outbreak of secretory diarrhoea (has low infectious dose) **Adenovirus** - Secretory diarrhoea in <2yo or Immunosuppressed **Rotavirus** - dsDNA affecting mucosa of small intestine - Nursery outbreaks (<6yo) - most children by age of 6 will have abs to at least 2 type - recurrent infection eventually leads to life long immunity
43
Prevention measures against GI infections
- Handwashing!!!!!! - Food washing - Vaccination
44
Which causes of GI infections have available vaccines
* *Cholera* (serogroup O1) * *Campylobacter* * ETEC * *Salmonella typhi* * Rotavirus (rotarix (live, monovalent), rotateq (pentavalent), rotashield (used if risk of intussusception))

PATH FINAL (36 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions