CSIM 1.54: Major Bacteria Producing Gastroenteritis

Question 1

What is gastroenteritis?

Answer 1

Inflammation of the stomach and intestines

Question 2

What parasitic causes of GI illness exist?

Answer 2

• Protozoa

* Helminths

Question 3

What are the common bacterial causes of gastroenteritis?

Answer 3

• Salmonella
  
  • E. coli
  • Shigella
  • Clostridium difficile
  • Campylobacter
  • S. aureus
  • Vibrio cholerae

Question 4

What are the host-related factors which control whether someone is likely to get bacterial gastroenteritis?

Answer 4

• Age
  
  • Immune factors (e.g. IgA levels)
  • Host receptors for microbial toxins
  • Host receptors for microbial adhesion
  • Intestinal motility
  • Nutritional status
  • Gastric acidity
  • GI flora competition

Question 5

What foods most frequently contain bacteria capable of causing gastroenteritis?

Answer 5

• Dairy products
  
  • Eggs
  • Meat

Question 6

Describe the pathogenic process of bacterial gastroenteritis

Answer 6

1) Bacteria escape the gastric acidity
2) Adhesion to the intestinal receptors allows establishment, multiplication and competition with existing gut flora
3) • Here, some bacteria invade into epithelial cells and submucosa towards lymph nodes causing abdominal pain
• Some bacteria invade the bloodstream, causing fever and systemic illness
• All bacteria produce toxins, which can lead to diarrhoea and vomiting

Question 7

What is a coliform and which bacterial causative agents of gastroenteritis can be described as coliforms?

Answer 7

Rod-shaped, gram-negative bacteria:
• E. coli
• Salmonella enterica
• Shigella

Question 8

In terms of gastroenteritis, what do the following do?

1) Enterotoxins
2) Cytotoxins

Answer 8

1) A toxin which leads to fluid secretion without mucosal damage (–> diarrhoea)
2) Mucosal damage causing dysentry (blood in stools)

Question 9

What is food poisoning?

Answer 9

A lay term referring to gastroenteritis caused by contamination by:
• Bacteria
• Bacterial toxins

NB: BACTERIA DONT HAVE TO BE PRESENT, toxins are enough to cause food poisoning

Question 10

What are the two prominent serotypes of Salmonella enterica? How many serotypes are there?

Answer 10

• Typhimurium
  
  • Enteritidis

2000 serotypes

Question 11

What does Salmonella enterica typhimurium do? What is the incubation period for this?

Answer 11

Invades the bloodstream from the gut, causing typhoid (fever with an eruption of red spots on the chest and abdomen and severe intestinal irritation)
• 10-14 days incubation (invasion after first week

Question 12

How long does salmonella food poisoning take to take affect?

Answer 12

Incubation period: 8-48 hours

Question 13

What is the most common cause of dysentry in the UK?

Answer 13

Bacillary dysentry by the four Shigella species releasing CYTOTOXINS

Question 14

How many species of Shigella are there?

Answer 14

four:
  •  S. dysentriae
  •  S. flexneri
  •  S. boydii
  •  S. sonnei

Question 15

How is E. coli serotyped

Answer 15

Based on:
  •  Lipopolysaccharide antigen (LBS
  •  Somatic antigen (O) 
  •  Flagella antigen (F) 
  •  Capsular antigen (K)

E.g.: O157:H7

Question 16

How does E. coli gastroenteritis often present?

Answer 16

Bloody diarrhoea (dysentry) due to cytotoxin release

Question 17

What is ‘rice water diarrhoea’ and what causes it? What are the other symptoms?

What pathogenesis causes these symptoms?

Answer 17

Completely white diarrhoea, caused by Vibrio cholerae
• Vomiting
• Hypovolumic shock
• Muscle cramps
• Death in 12-24 hours without treatment

Penetration of the mucous later of gut and release of cholera toxin 01
• Causes excessive loss of water and electrolytes from the gut
• Overproduction of cAMP causing reduced uptake of NaCl and increased secretion of bicarbonate and chloride ions

Question 18

Describe Vibrio genus:
• Gram
• Motility
• Shape

Answer 18

• Gram-negative
  
  • Motile
  • Curved rods

Question 19

How is cholera treated?

Answer 19

• Fast rehydration therapy
  
  • Oral rehydration therapy
  • Antibiotics

Question 20

Which antibiotics are effective in the treatment of cholera?

Answer 20

• Tetracycline
  
  • Chloramphenicol
  • Co-trimoxazole

Question 21

What is the main source of infection of Campylobacter?

Answer 21

animals (60% chickens)

Question 22

Is Campylobacter often a source of food poisoning? Why?

Answer 22

No - does not multiply in foods as it is fragile

Question 23

Describe the genus Clostriudium
  •  Gram
  •  Shape
  •  Aerobicity 
  •  Spores

What are the predominant species of Clostridium?

Answer 23

• Gram positive
  
  • Bacilli
  • Anaerobes
  • Spore forming

Clostridium:
• C. difficile
• C. perfringens
• C. sporogenes

Question 24

Describe how Clostridium perfringens often causes infection

What are the symptoms of C. perfringens?

Answer 24

• Creates heat-resistant spores, which are difficult to cook in bulk cooking
  
  • Spores germinate and multiply when food is consumed
  • The bacteria release endotoxin

Fever, D&V

Question 25

What is the cause of antibiotic-associated bacteria? Describe what this means What does this bacterium produce? How is this treated?

Answer 25

C. difficile: • Antibiotics disrupt the gut flora • This allows C. diff an opportunity to proliferate with little competition Two enterotoxins: • Enterotoxin A • Enterotoxin B Treated with: • Oral/IV metronidazole • Oral vancomycin

Question 26

``` Describe the pathogenesis of S. aureus gastroenteritis, including: • Transmission • Toxin • Incubation • Symptoms • Resolution ```

Answer 26

* Food-bourne * Enterotoxin B-mediated * 2-4 hour incubation * Violent vomiting and then profuse diarrhoea * Self-limiting within 24 hours

Question 27

Which bacterium causes fried rice food poisoning? Gram and shape?

Answer 27

Bacillus cereus. Gram positive bacilli.

Question 28

Which antibiotics are overall used for severe gastrointestinal infection?

Answer 28

* Ciprofloxacin * Azithromycin * Doxycycline * Metronidazole

Question 29

How is rehydration achieved?

Answer 29

* Oral rehydration solution | * IV Ringer's lactate