Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MedEd + PathSoc + Laz's Qs + Romesh Path > Micro 2: GI infections > Flashcards

Micro 2: GI infections Flashcards

1
Q

List some reportable GI infections

A

Campylobacter

Salmonella

Shigella

Escherichia coli O157

Listeria

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

What are the main characteristics of secretory diarrhoea?

A

Watery diarrhoea (no inflammatory cells in stool)

No fever

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

What are the main characteristics of inflammatory diarrhoea v secretory?

A

Inflammatory:
Fever
Diarrhoea (inflammatory cells present, may be bloody)

Secretory:
Watery diarrhoea (no inflammatory cells in stool)
No fever

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

List some examples of severe GI infections that produce a fever with little stool changes.

A

Salmonella typhi

Enteropathogenic Yersinia

Brucella

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

Describe the mechanism by which Vibrio cholerae causes secretory diarrhoea.

A

The cholera toxin has subunits A and B which stimulate adenylate cyclase

This leads to the production of cAMP which opens chloride channels on the membranes of enterocytes

Chloride efflux into the lumen is accompanied by water and electrolyte loss

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

What are superantigens?

A

Toxins that bind to TCR outside the peptide binding region

They cause large scale activation of T cells leading to massive cytokine production by CD4 cells

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

What type of toxin is produced by Staphylococcus aureus? what does this trigger

A

Enterotoxin – this is an exotoxin that can act as a superantigen in the GI tract triggering the release of IL1 and IL2

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

What type of organism is Staphylococcus aureus?

A

Catalase and coagulase positive, Gram-positive coccus that appears in clusters

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

How is Staphylococcus aureus spread and what kind of GI symptoms can it cause?

A

Spread by skin lesions on food handlers

Causes prominent vomiting and watery, non-bloody diarrhoea

NOTE: it is self-limiting so does not require treatment

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

What type of organism is Bacillus cereus?

A

Gram-positive rods that are spore-forming

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What type of toxins does B. cereus produce?

A

Heat stable emetic toxin

Heat labile diarrhoeal toxin

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

What type of GI symptoms does B. cereus cause?

A

Watery, non-bloody diarrhoea

NOTE: it can cause bacteraemia and cerebral abscesses in vulnerable populations

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

Name three types of Clostridium infection and describe the diseases that they cause.

A

Clostridium botulinum – causes botulism
From canned food:
- Causes disease due to preformed toxin which blocks acetylcholine release at peripheral nerve synapses resulting in paralysis
- Treated with antitoxin

Clostridium perfringens – food poisoning
From reheated food:
- Generates a superantigen that mainly affects the colon
- Causes watery diarrhoea and cramps that last 24 hours

Clostridium difficile – pseudomembranous colitis:
- Hospital-acquired infection related to antibiotic use

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

Which antibiotics are most commonly implicated in C. difficile colitis?

A

Cephalosporins

Clindamycin

Ciprofloxacin

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

How is C. difficile colitis treated?

A

Metronidazole

Vancomycin

Stop the offending antibiotic

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

What type of organism is Listeria monocytogenes?

A

Gram-positive, rod-shaped, facultative anaerobe

Beta-haemolytic, aesculin-positive with tumbling motility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What GI symptoms does Listeria tend to cause?

A

Watery diarrhoea, cramps, headache, fever and a little vomiting

NOTE: it comes from refrigerated food (e.g. unpasteurised dairy)

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

How is Listeria infection treated?

A

Ampicillin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What type of organisms are Enterobacteriaceae?

A

Facultative anaerobes

Lactose fermenters

Oxidase-negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Name and describe the different types of E. coli (GRAM -VE ROD) infection.

A

ETEC (enterotoxigenic) – toxigenic, main cause of travellers’ diarrhoea

EPEC (Enteropathogenic) – pathogenic, infantile diarrhoea

EIEC (Enteroinvasive) – invasive, dysentery

EHEC (Enterohaemorrhagic) – haemorrhagic, caused by E. coli O157:H7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What causes haemolytic uraemic syndrome?

A

EHEC shiga-liked verocytotoxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What type of bacteria are Salmonellae? what do they make on what agar?

A

Non-lactose fermenting, Gram-negatives

Produce hydrogen sulphide (form black colonies)

Grows on TSI agar, XLD agar and selenite F broth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Which antigens are found on Salmonellae?

A

Cell wall O (groups A-I)

Flagellar H

Capsular Vi (virulence, antiphagocytic)

NOTE: differences in these antigens help identify types of Salmonellae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

List three species of Salmonella.

A

Salmonella typhi (and paratyphi)
Salmonella enteritidis
Salmonella choleraesuis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How is Salmonella transmitted?

A

Via infected meat products (but it can also be transmitted by pets (mainly reptiles))

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe the presentation of Salmonella enteritidis.

A

Enterocolitis – loose stools
Transmitted by poultry, eggs and meat

Self-limiting diarrhoea that is non-bloody
No fever
Bacteraemia is rare

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Describe the presentation of Salmonella typhi - where does it multiply

A

Transmitted only by humans

Multiplies in Peyer’s patches and spreads via the endoreticular system

Slow onset fever and constipation

May cause splenomegaly, rose spots, anaemia and leucopaenia

Blood cultures may be positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Which subset of patients are at increased risk of Salmonella bacteraemia?

A

Sickle cell patients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How is Salmonella typhi treated?

A

Ceftriaxone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What are some key microbiological features of Shigella?

A

Non-lactose fermenter

Does NOT produce hydrogen sulphide

Non-motile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Which antigens are seen on Shigella?

A

Cell wall O antigens

Polysaccharide (groups A-D)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

List some types of Shigella.

A

Shigella sonnei

Shigella dysenteriae

Shigella flexneri (MSM)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the most effective bacterial enteric pathogen and why?

A

Shigella – it has the lowest infective dose (50)

NOTE: Shigella has no animal reservoir and no carriers

34
Q

How does Shigella infection manifest? what does it produce? mx?

A

Dysentery – severe diarrhoea with blood and mucus in the faeces

NOTE: Shigella produces shiga toxin
NOTE: avoid antibiotics when treating Shigella

35
Q

What are the microbiological features of Vibrio?

A

Comma-shaped

Late lactose-fermenters

Oxidase-positive

Gram-negative

CLOG = vibrio

36
Q

What are the different groups of Vibrio cholerae?

A

O1 – causes epidemics

Non-O1 – sporadic, non-pathogens

37
Q

What type of GI disturbance does Vibrio cholerae cause? mx?

A

Produce watery diarrhoea without inflammatory cells

Treat the losses (water and electrolytes)

38
Q

Name and describe the key features of other types of Vibrio.

A

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

39
Q

What are the main microbiological features of Campylobacter?

A

Comma-shaped

Microaerobphilic

Oxidase-positive

Gram-negative

Motile

40
Q

Describe the presentation of Campylobacter jejuni infection? transmission

A

Watery, foul-smelling diarrhoea, bloody stools, fever and severe abdominal pain

NOTE: transmitted by food and water that has been contaminated by animal faeces

41
Q

How is Campylobacter infection treated?

A

Only treated if immunocompromised

Erythromycin or ciprofloxacin

42
Q

What are some complications of Campylobacter infection?

A

Guillain-Barre syndrome

Reactive arthritis

43
Q

Which other bacterial organisms can cause GI disease?

A

Yersinia enterocolitica – non-lactose fermenter that causes enterocolitis or mesenteric adenitis (also associated with reactive arthritis)

Mycobacteria

44
Q

Describe the pathophysiology of diarrhoeal illness caused by Entamoeba histolytica?

A

Ingestion of cysts 🡪 trophozoites move into the ileum 🡪 colonise the colon 🡪 causes flask-shaped ulcers

45
Q

Describe the presentation of GI infection by Entamoeba histolytica.

A

Dysentery, flatulence, tenesmus, liver abscess

46
Q

How is Entamoeba histolytica infection diagnosed and treated?

A

Diagnosis: stool microscopy, serology of invasive disease

Treatment: metronidazole + paromomycin

47
Q

What are the key microbiological features of Giardia lamblia?

A

Pear-shaped trophozoites

Two nuclei

Four flagellae and a suction disc

48
Q

Outline the pathophysiologiy of GI disease caused by Giardia.

A

Transmitted by ingestion of cyst from faecally contaminated water

Excystation in the duodenum leads to trophozoite attachment

Results in malabsorption of protein and fat

Presentation: foul-smelling non-bloody diarrhoea, cramps, flatulence, NO fever

49
Q

How is Giardia infection diagnosed and treated?

A

Stool microscopy
ELISA
String test

Treatment: metronidazole

50
Q

What are the main features of Cryptosporidium parvum? stain? mx?

A

Causes severe diarrhoea in the immunocompromised
Oocysts can be seen in the stool using modified
Kinyoung acid fast stain

Treated by boosting the immune system

51
Q

What is the predominant strain of norovirus?

A

GII.4

52
Q

What is rotavirus and what does it cause?

A

dsRNA virus

Replicates in the mucosa of the small intestine and causes secretory diarrhoea with no inflammation

NOTE: exposure to natural infection twice will confer lifelong immunity

53
Q

List some other viruses that can cause diarrhoeal illnesses.

A

Adenovirus (types 40 and 41 can cause non-bloody diarrhoea in < 2 year olds)

Poliovirus

Enterovirus (e.g. coxasckie, echovirus)

Hepatitis A

54
Q

Which causes of diarrhoeal illness have available vaccines?

A

Cholera (serogroup O1)

Campylobacter

ETEC

Salmonella typhi

Rotavirus (rotarix (live, monovalent), rotateq (pentavalent), rotashield (used if risk of intussusception))

55
Q

Who is responsible for collecting reports of diarrhoeal illness and identifying outbreaks?

A

Health Protection Unit (HPU)

56
Q

Main cause of gastroenteritis?

A

Viral

57
Q

Ix of suspected c.diff? of protazoa or parasite?

A 
Stool MCS (standard)
\+
C. Diff toxins
\+/-
OCP -  ova, cysts and parasite test (protazoa / parasites)
58
Q

Mx of gastroenteritis ?

A

Conservative:

  • Side room, PPE, wash hands
  • IV fluids, electrolytes, oral rehydration

Medical:
Loperamide (CI in Abx-assc colitis, fever and PR bleeding)
Ciprofloxacin (given empirically in severe / known bacterial) - strong v gram -ve

59
Q

An elderly woman has type 6 stool which is green and mucoid in appearance. She is on the 6th day of IV ceftriaxone (=cephalosporin).

What is the likely causative organism?

A

Clostridium difficile

RFs in this case:
- Abx starting w/ C (co-amoxiclav, cephalosporins, clindamycin)

60
Q

What causes pseudomembranous colitis?

What is the treatment + alternatives?

A

C. Diff - treated w/ PO Vancomycin- better for severe (also PO Metronidazole)

Alternative - faecal transplant
Surgical - Colectomy

61
Q

Deadliest strain of C. Diff?

A

Ribotype 027

62
Q

Infants under 12 months should not be fed honey due to an increased risk of food poisoning caused by which of organism? What unusual symptom is suggestive of this? Mx?

A

Clostridium Botulinum - RF = Honey (vaccum packed foods) (Gram+Ve)

Causes descending paralysis - Toxin blocks ACh release from peripheral nerves

Mx:
• Anti-toxin IM injections

63
Q

A woman develops vomiting a few hours after reheating and ingesting Chinese fried rice.

What is the most likely causative organism? Incubation?

A

Bacillus cerus - RF = Reheated rice (often chinese fried in Qs) (gram +ve)

Quick incubation period - often symptoms on same day

64
Q

A South American man presents to a doctor in the UK with fever and bloody
diarrhoea. Investigations reveal a cyst in the right lobe of the liver.

What is the most likely causative organism? What unusual symptoms does this cause? Mx?

A

Entamoeba histolytica - HAS 4 NUCLEI (Parasite)

Can cause liver abscesses and (flask-shaped) ulcers in caecum

Mx:

  • Metronidazole (useful for parasite) + paromomycin
  • Liver abscess = US guided drainage
65
Q

What organism is responsible for ANCHOVY PASTE CONSISTENCY on US guided draingae of Liver abscess?

A

Entamoeba Histolytica

66
Q

A man develops foul-smelling diarrhoea and cramping pain 5 days after eating chicken at his neighbour’s barbeque.

What is the most common causative organism? Symptoms? Mx?

A) Campylobacter jejuni
B) Shigella
C) Escherichia coli 0157
D) Salmonella typhi
E) Vibrio cholerae
A

Campylobacter jejuni - RF = Poultry (GRAM -VE)

Symptoms:

  • CHESS - Bloody diarrhoea
  • CRAMPY abdo pain - SBA land for campylobacter
  • Watery diarrhoea

Mx?
Macrolide eg. clarithromycin

67
Q

Comma-shaped organism that is associated with Guillain-Barre and Reactive arthritis? what is another organism that is comma-shaped?

A

Campylobacter Jejuni

Vibrio cholerae

68
Q

An aid worker returns from camp in Yemen. He has profuse watery diarrhoea,
which he describes as looking like water that rice has been cooked in. He is very dehydrated.

What is the likely cause of his diarrhoea? Symptoms -pathognmonic?

A

Vibrio Cholerae - RF = Africa + Middle East

Symptoms:
- (Profuse) watery diarrhoea
= RICE WATER STOOLs

69
Q

A 42 year old man who recently returned from a trip to India has presented with a fever of 39.6°C and abdominal pain but no history of diarrhoea. His blood cultures
have grown Gram-negative bacilli and his Malaria rapid diagnostic test is negative.

What is the most appropriate antibiotic therapy? What organism? What if they develop diarrhoea after mx?

A

Gram-ve bacilli + RF = Travel from India (+ Africa) -> Salmonella Typhii

Symptoms:

  • Constipation
  • Rose spots

Mx:
Ceftriaxone (+ azithromycin) -> if develop diarrhoea consider C. Diff

70
Q

What type of salmonella is associated w/ poultry? main symptom? mx?

A

Salmonella Enteritidis

Causes bloody diarrhoea

mx = ciprofloxacin

71
Q

Most common cause of travellers diarrhoea?

A

Escherichia coli

Enterotoxigenic e. coli - ETEC

72
Q

A boy presents with diarrhoea, unexplained bruises all over his body and feeling fatigued. He recently visited his grandparents in Wiltshire.

What is the most likely causative organism?

A

This is Haemolytic Uraemic Syndrome which can be caused by E. Coli 0157 (GRAM -VE)

Mention of Wiltshire - countryside = likely to pick up this variant from farm animals?

73
Q

A nurse on the care of the elderly ward complains of vomiting and diarrhoea. She
mentions that many of her patients also had similar symptoms.

What is the most likely causative organism?

A) Cryptosporidium parvum
B) Rotavirus
C) Adenovirus
D) Norovirus
E) Staphylococcus aureus
A

Norovius AKA winter vomiting bug that is associated w/ outbreaks (hospitals + nursing homes) -> D+V

74
Q

Organisms other than Norovirus that can cause vomiting + in who?

A

Rotavirus can also cause vomiting however is vaccinated for hence consider in young children - may not be vaxd or antivax

Adenovirus - RF = Immunocompromised or poor hygiene (faeca-oral transmission)

75
Q

A HIV-positive patient presents with long-standing diarrhoea. A stool sample is
sent for analysis and the organism is visualised after Kinyoun staining.

What is the most likely causative organism? RFs, symptoms and ix?

A) Cryptosporidium parvum
B) Giardia lamblia
C) Entamoeba histolytica
D) Adenovirus
E) Staphylococcus aureus
A

A) Cryptosporidium parvum

Long-standing diarrhoea - generally points towards a parasitic cause and Kinyoun staining is linked w/ Cryptosporidium parvum

RF = Immunocompromised

Symptoms = prolonged diarrhoea

Ix =

76
Q

A HIV-positive patient presents with long-standing diarrhoea. A stool sample is
sent for analysis and the organism is visualised after Kinyoun staining.

What is the most likely causative organism? RFs, symptoms and ix?

A) Cryptosporidium parvum
B) Giardia lamblia
C) Entamoeba histolytica
D) Adenovirus
E) Staphylococcus aureus
A

A) Cryptosporidium parvum

Long-standing diarrhoea - generally points towards a parasitic cause and Kinyoun staining is linked w/ Cryptosporidium parvum

RF = Immunocompromised

Symptoms = prolonged diarrhoea

Ix = Stool OCP + Kinyoun stain

Mx = Paromomycin + improve immunity (eg HIV mx)

77
Q

Giardia lamblia - RFs, Symptoms, Ix, Mx, Pathgmnoic term?

A

RF = Poor hygiene (faeco-oral)
+ Immunocompromised

Symptoms = Prolonged diarrhoea (watery, foul smelling)

Ix = Stool ELISA (more used), String test (more used in SBAs)

Mx = Metronidazole

Pathagnomnic = 2 pear-shaped nuclei

78
Q

MoA of C. diff?

A

Toxin A -enterotoxin + Toxin B -cytotoxic -> Causes pseudomembranous colitis

79
Q

What are the causes of BLOODY DIARRHOEA?

A

CHESS

Campylobacter
Haemorrhagic E.coli (0157 -> HUS)
Entamoeba histolytic
Salmonella
Shigella
80
Q

What is generally given to gram -ve causes of gastroenteritis?

A

Ciprofloxacin

MedEd + PathSoc + Laz's Qs + Romesh Path (99 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions