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7. Microbiology II > Gram Negative GI Infections > Flashcards

Gram Negative GI Infections Flashcards

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1
Q

List 7 gram negative bacteria which cause GI infection.

A 
Campylobacter
Salmonella
Shigella
Vibrio cholera
E. coli
Yersinia enteroclitica
H. pylori
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2
Q

Describe the microbiological features and epidemiology of campylobacter. Consider:

MICROBIOLOGY:
Structure
Growth conditions
Types of campylobacter

EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs

A 
MICROBIOLOGY
Curved gram negative bacilli
Growth conditions:
-Microaerophilic
-Thermophilic (42C)
Types of campylobacter:
-C. jejuni
EPIDEMIOLOGY
Seasonal peaks in May/September
Transmission:
-Contaminated food (esp poultry)
-Contaminated milk/water
Outbreaks: rare
Animal reservoirs: numerous (e.g. poultry, cattle, sheep)
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3
Q

Describe the pathogenesis of campylobacter infections. (2)

A
  1. Inflammation, ulceration and bleeding in small/large intestines
  2. May cause bacteraemia, e.g. in
    a. Extremes of age
    b. Immunocompromised patients
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4
Q

Describe the clinical features of campylobacter infection. Consider:

a) Incubation period
b) Duration
c) Symptoms
d) Complications

A

Incubation period: 2-5 days

Duration: 2-10 days

Symptoms:

  • Bloody diarrhoea
  • Abdominal cramps
  • Fever

Complications:
-Guillain-Barré syndrome

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5
Q

How is campylobacter infection treated? Consider:

a) Severe/prolonged infection
b) Invasive infection

A

SEVERE INFECTION:
Clarithromycin

INVASIVE INFECTION:
Quinolones
Aminoglycosides (e.g. gentamicin)

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6
Q

List the 6 types of E. coli which cause diarrhoea.

A 
Enteropathogenic (EPEC)
Enterotoxigenic (ETEC)
Enterohaemorrhagic (EHEC)
Enteroinvasive (EIEC)
Entero-aggregative (EAEC)
Diffuse-aggregative (DAEC)
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7
Q

Describe the epidemiology of:

a) Enteropathogenic E coli
b) Enterotoxigenic E coli
c) Enterohaemorrhagic E coli

A

EPEC:
Sporadic

ETEC:
Major cause bacterial diarrhoea

EHEC:
Quite rare

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8
Q

Describe the pathogenesis of diarrhoea in enteropathogenic E coli infections. (3)

A
  1. Bacteria adhere to gut mucosal cells via pilli
  2. This forms an “attaching and effacing” lesions
    a. Mediated by intimin and Tir (translocated intimin receptor)
    b. Tir is produced by EPEC, then injected into gut cells
  3. This causes disruption of intestinal microvilli
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9
Q

List the clinical features of enteropathogenic E coli (EPEC). Include:

a) Incubation period
b) Duration
c) Symptoms (4)

A

Incubation period: 1-2 days
Duration: 1-several weeks

Symptoms:
Watery diarrhoea
Abdominal pain
Vomiting
Fever
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10
Q

Describe the pathogenesis of enterotoxigenic E coli (ETEC). (2)

A
  1. Heat labile toxin (LT)
    a. Analogue of cholera toxin; similar symptoms
    b. Destroyed by heat
  2. Heat stable toxin (ST)
    a. Similar mode of action to LT
    b. NOT destroyed by heat
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11
Q

Describe the clinical features of enterotoxigenic E coli (ETEC). Include:

a) Incubation period
b) Duration
c) Symptoms (3)

A

Incubation period: 1-7 days
Duration: 2-6 days

Symptoms:
Watery diarrhoea
Abdominal pain
Vomiting

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12
Q

Describe the pathogenesis of enterohaemorrhagic E coli (EHEC). (4)

A
  1. Bacteria adhere to gut mucosal cells via pili
  2. This forms an attaching and effacing lesion
    a. Mediated by: intimin and Tir (translocated intimin receptor)
  3. EHEC produce shiga-like toxins, which damage the intestinal epithelium
    a. May also damage glomerulus, causing renal failure
  4. EHEC produce other toxins:
    a. Shiga toxin (STEC)
    b. Verotoxin (VTEC)
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13
Q

Describe the clinical features of enterohaemorrhagic E coli (EHEC). Include:

a) Incubation period
b) Duration
c) Symptoms
d) Complications

A

Incubation period: 1-7 days
Duration: 5-10 days

Symptoms:
Blood diarrhoea
Vomiting
Abdominal pain

Complications:
Haemolytic uraemic syndrome

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14
Q

Describe the microbiological features and epidemiology of salmonella. Consider:

MICROBIOLOGY:
Structure
Types of salmonella

EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs

A 
MICROBIOLOGY
Structure:
-gram negative bacilli
-non-lactose fermenters
Types of salmonella:
-S. enterica
-S. typhi
-S. paratyphi
EPIDEMIOLOGY
Transmission:
-Contaminated food
-Person-person
Outbreaks:
-Frequent (bc CAN multiply in food)
Animal reservoirs:
-Multiple
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15
Q

Describe the pathogenesis of salmonella infection. (3)

A
  1. Bacteria invade epithelial cells in the distal small intestine, causing inflammation and diarrhoea
  2. Bacteraemia may occur in vulnerable patients
  3. Metastatic infection may occur, causing:
    - Osteomyelitis
    - Septic arthritis
    - Meningitis
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16
Q

Describe the clinical features of salmonella infection. Consider:

a) Incubation period
b) Duration
c) Symptoms (3)
d) Complications (3)

A

Incubation period: 12-72 hours
Duration: 2-7 days

Symptoms:
Watery diarrhoea
Vomiting
Fever

Complications:
Osteomyelitis
Septic arthritis
Meningitis

17
Q

Describe the microbiological features and epidemiology of shigella. Consider:

MICROBIOLOGY:
Structure
Growth conditions
Types of shigella

EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs

A 
MICROBIOLOGY
Structure:
-Gram negative bacilli
-Non-lactose fermenter
Types of shigella:
-S. sonnei
-S. boydii
-S. flexneri
-S. dysenteriae
EPIDEMIOLOGY
Transmission:
-Person-person
-Faeco-oral
Outbreaks:
-Frequent (bc person-person transmission)
Animal reservoirs:
-None except humans
18
Q

Describe the pathogenesis of shigella infection.

A
  1. Organisms attach to and colonise the mucosal epithelium of the terminal ileum/colon
  2. Produce Shiga toxin, which damages the intestinal epithelium
    a. Also targets glomerular endothelium
    b. Therefore can cause renal failure and HUS
19
Q

Describe the clinical features of shigella infection. Consider:

a) Incubation period
b) Duration
c) Symptoms (3)
d) Complications (2)

A

Incubation period: 1-3 days
Duration: 2-7 days

Symptoms:

  • Initial watery diarrhoea (then becomes bloody)
  • Cramping abdominal pain
  • Fever

Complications:

  • Renal failure
  • Haemolytic uraemic syndrome (HUS)
20
Q

Describe the microbiological features and epidemiology of vibrio cholerae. Consider:

MICROBIOLOGY:
Structure
Growth conditions
Types of v. cholerae

EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs

A 
MICROBIOLOGY
Structure:
-Comma shaped gram negative bacilli
-Sucrose fermenter
Types of v. cholerae:
-Serotype O1 (El Tor)
-Serotype O139
-Vibrio parahaemolyticus
EPIDEMIOLOGY
Transmission:
-Contaminated food/water
Outbreaks:
-Endemic in SE Asia, Africa, S America
Animal reservoirs:
-None except humans
21
Q

Describe the pathogenesis of cholera. (3)

A
  1. Bacteria penetrate the intestinal mucous (via flagella and mucinase enzymes)
  2. Bacteria attach to mucosa via specific receptors
  3. Bacteria produce cholera toxin (CTX)
    a. This causes diarrhoea
22
Q

Describe the clinical features of cholera. Consider:

a) Incubation period
b) Symptoms (2)
c) Complications (4)

A

Incubation period: 12 hours - 5 days

Symptoms:

  • Severe and profuse watery diarrhoea (rice water stool)
  • Dehydration

Complications:

  • Hypokalaemia
  • Metabolic acidosis
  • Hypovolaemic shock
  • Cardiac failure
23
Q

How is cholera treated? (2)

State administration for any drugs given.

A

Rehydration therapy (oral or IV)

Tetracycline antibiotics (oral or IV)

24
Q

Describe the microbiological features and epidemiology of campylobacter. Consider:

MICROBIOLOGY:
Structure

EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs

A

MICROBIOLOGY
Structure:
-Gram negative bacilli

EPIDEMIOLOGY
Transmission:
-Raw/undercooked pork
-Pasteurised milk (can survive/multiple in fridge temperatures)
Animal reservoirs:
-Include pets
25
Q

Describe the pathogenesis of yersinia enterocolitica infection. (2)

A
  1. Invades terminal ileum

2. Causes inflammation of mesenteric lymph nodes

26
Q

Describe the clinical features of yersinia enterocolitica infection. Consider:

a) Incubation period
b) Duration
c) Symptoms (4)

A

Incubation period: 4-7 days
Duration: 1-2 days

Symptoms:

  • Diarrhoea (may/may not be bloody)
  • Abdominal cramps
  • Fever
  • Mesenteric adenitis
27
Q

Describe the microbiological features and epidemiology of H. pylori. Consider:

MICROBIOLOGY:
Structure
Growth conditions
Diagnosis

EPIDEMIOLOGY:
Transmission
Animal reservoirs

A 
MICROBIOLOGY
Structure:
-Spiral shaped gram negative bacilli
Growth conditions:
-Microaerophilic
-Live in acid (produce urease)
Diagnosis:
-Faecal antigen test
-Urea breath test
EPIDEMIOLOGY
Transmission:
-Faeco-oral
-Oral-oral
Animal reservoirs:
-Human only
28
Q

Describe the pathogenesis of H. pylori infection. (2)

A
  1. Cytotoxin production

2. Bacteria contain a range of factors which promote adhesion and colonisation

29
Q

Describe the clinical features of H. pylori infection. Consider:

a) Complications (3)

A 
Duodenal ulcers (90%)
Gastric ulcers (70-80%)
Increased risk of gastric cancer
30
Q

How is H. pylori infection treated? (2)

A

PPI, e.g.

  • Omeprazole
  • Lansoprazole

Antibiotics, e.g.

  • Clarithromycin
  • Metronidazole

7. Microbiology II (12 decks)

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