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Infection Diseases > Escherichia Coli > Flashcards

Escherichia Coli Flashcards

1
Q

What is the gram stain of E.coli?

A

Gram negative bacilli

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2
Q

What is escherichia coli?

A

Gram negative bacilli
Lactose fermenting - use lactose of energy source
Anaerobic

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3
Q

What can E. Coli cause?

A

Diarrhoea
Extra-intestinal infections e.g. UTIs

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4
Q

Transmission of E. Coli

A

Hand to mouth contact
Consumption of contaminated food

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5
Q

Identifying E. coli in a lab

A

Grow as pink colonies on MacConkey agar as lactose fermenters - lactic acid changes colour
Pink gram negative bacilli gram stain

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6
Q

Colour of lactose fermenting colonies on MacConkey agar

A

Pink
Produce lactic acid&raquo_space; changes colour of indicator

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7
Q

Colour of non-lactose fermenting colonies on MacConkey agar

A

Yellow

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8
Q

Explain the colour change in MacConkey agar

A

Contains lactose and pH indicator
pH indicator goes red with acid pH

Pink - lactose fermenting colonies
Yellow - non-lactose fermenting colonies

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9
Q

How does serology work with E. Coli?

A

Using antibodies to detect different bacterial surface antigens
K - capsule
O - LPS (lipopolysaccharide)
F - fimbriae
H - flagella

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10
Q

Where is E.coli normal in body?

A

In large bowel

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11
Q

What is a potential function of E.coli?

A

Protection against invasion by pathogenic species e.g. salmonella

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12
Q

What are the 6 pathotypes of diarrhoeagenic E. Coli that cause diarrhoea?

A

Enterotoxigenic E. Coli (ETEC)
Enteropathogenic E. Coli (EPEC)
Enteroaggregative E. Coli (EAEC)
Enteroinvasive E. Coli (EIEC)
Diffusely adherent E. Coli (DAEC)
Shiga toxin producing E. Coli (STEC)

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13
Q

What are the most common E. Coli pathotypes in children in developing world?

A

Enteropathogenic E. Coli (EPEC)
Enteroinvasive E. Coli (EIEC)

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14
Q

What is the most common E. Coli pathotype in immunocompromised persons?

A

Enteroaggregative E. Coli (EAEC)

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15
Q

What does enterotoxigenic E. Coli cause?

A

Travelers’ diarrhoea

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16
Q

What is the most common cause of travellers’ diarrhoea?

A

Enterotoxigenic E. Coli

17
Q

Transmission of Enterotoxigenic E. Coli?

A

Faecal-oral

18
Q

What toxins are produced from enterotoxigenic E. Coli?\

A

Heat stable toxin (ST)
Heat liable toxin (LT)

19
Q

What effect of enterotoxigenic E. Coli toxins have?

A
  • Stimulate the lining of intestines
  • Cause them to secrete excessive fluid&raquo_space; profuse water diarrhoea and abdominal cramping
20
Q

What effect do heat stable toxins and heat liable toxins have?
What produce them?

A
  • Stimulate the lining of intestines
  • Cause them to secrete excessive fluid producing profuse water diarrhoea and abdominal cramping

Enterotoxigenic E. Coli

21
Q

What does Enteropathogenic E. Coli cause?

A
  • The localised disappearance of microvilli
  • Attaches to the host cell surface&raquo_space; forming attaching and effacing lesions.
22
Q

What are other names for shiga toxin producing E. Coli?

A

Verocytotoxic E. Coli (VTEC)
Enterhaemorrhagic E. Coli (EHEC)

23
Q

What does shiga toxin producing E. coli cause?

A

Haemorrhagic colitis&raquo_space; bloody diarrhoea
Haemolytic uraemic syndrome

24
Q

What is haemolytic uraemic syndrome?

A

Triad of conditions:
- Acute renal failure
- Haemolytic anaemia
- Thrombocytopenia

25
Q

Explain the invasion of shiga toxin producing E.coli

A
  • B sub unit of shiga toxin binds to Gb3 on host cell surface
  • toxin is endocytosed + transported to Golgi apparatus + endoplasmic reticulum
  • during transports, the A chain is cleaved into A2 fragment + enzymatically active A1 fragment
  • A fragments held together by disulfide bonds until toxin reaches ER where A1 fragment is released
  • A1 fragment goes to cytosol
  • A1 fragment inactivates ribosome&raquo_space; inhibits protein synthesis&raquo_space; cell death
26
Q

What strain of E. Coli causes extra intestinal diseases?

A

Extra-intestinal pathogenic E. Coli (ExPEC)

27
Q

What does extra-intestinal pathogen E. Coli cause?

A

Disease outside intestinal tract

28
Q

Virulence factors for extra-intestinal infections

A

Adhesions
Iron acquisition systems
Protections invasions
Toxins

29
Q

Why are UTIs more likely in women than men?

A

Anatomical differences between women and men
Shorter and easier route for bacteria to enter urethra from rectum in women

30
Q

Complications of cystitis

A

Frequent + urgent urination
Dysuria - painful
Nocturia - wake up in night
Hematuria - blood
Malaise

31
Q

Symptoms of pyelonephritis

A

Back and/or flank pain
Fevers + chills
Nausea
Vomiting
Anorexia

32
Q

Prevention of E. Coli caused diarrhoea

A
  • Avoid food + drink that could be contaminated e.g. raw meat, seafood + poultry, unpasteurised dairy products, street food, untreated water in areas lacking chlorination
  • Wash hands
33
Q

Treatment of E. Coli caused diarrhoea

A
  • Most will recovered after a few days without treatment
  • Clear liquids to prevent dehydration + loss of electrolytes
  • oral rehydration solution
  • Avoid antibiotics
34
Q

Treatment of UTIs

A

Antibiotics
trimethoprim
nitrofurantoin

35
Q

Why are urine samples in labs unrepresentative of the majority of UTIs?

A

They are often UTIs which haven’t resolved
Have antibiotic resistant bacteria

36
Q

Virulence factors of uropathogenic E. coli

A

Adhesions
Lipopolysaccharide

37
Q

What is the classification of microbes of E. Coli?

A

Prokaryote (bacteria)

38
Q

What is the mode of action of trimethoprim?

A

Inhibits folic acid synthesis

Infection Diseases (22 decks)

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