E-coli Flashcards by Rebekah Agunede

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Escherichia coli

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Gram stain

Negative rods (red stain)

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Microbe type

Anaerobic
Motile (flagellum)
Part of large bowel microbiota (multiple serotypes)

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Family type E-coli

Enterobacteriales

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What does one health ecology of ecoli mean?

Present in animals, humans and environment
Transmission can occur between these
Challenges with resistant serotypes

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Ecoli under micorscope

Gram negative rods
Pile up and form colonies (from division)

(ribosome, nucleoid, plasma membrane)

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How E-coli identified in lab?

MacConkey Agar - contains lactose and pH indicator

E-coli use lactose sugar as fuel and produce lactic acid waste product (decreases pH, turns indicator pink)

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MacConkey Agar e-coli result

Lactose fermenting so stains PINK

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How are different e-coli’s typed?

Serology (antibodies and antigens)
Metabolic profiling
Genomic diversity (whole genome sequencing, DNA hybridisation)

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Antigens present on e-coli

K - capsule
O - lipopolysaccharide wall
F - fimbriae
H - flagella

(KOFH)

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Genetic diversity of e-coli

IMMENSE

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E-coli function large bowel

Large bowel microbiota (humans & animals)

Protects against invasion of pathogenic species (salmonella)

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What can e-coli cause?

Intestinal infections (diarrhoea)

Extra-intestinal infections:
UTI
Biliary tract
Intra-abdominal abscess
Blood stream infection

NEONATAL MENINGITIS

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What determines pathology of e-coli?

Presence of virulence factors on specific e-coli strains

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How does e-coli invade?

Different ways depending on subtype/strain

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Six causes of e-coli diarrhoea

Entero:
toxigenic e.coli (ETEC)
pathogenic (EPEC)
aggregative (EAEC)
invasive (EIEC)

Diffusely adherent (DAEC)
Shiga toxin producing (STEC verocytotoxin producing/haemorrhagic)

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Most common diarrhoea e.coli children of developing world

Enteropathogenic

Enteroinvasive

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Immunocompromised e.coli

EAggEC

Enterotoxigenic e.coli

Travelers diarrhoea

Faecal-oral

What toxins does ETEC produce? What do they do?

Heat stable toxin (ST)
Heat labile toxin (LT)

stimulate lining to secrete excessive fluid = diarrhoea and cramping

Less common ETEC symptoms

Fever
Nausea
Loss of appetite
Headache 
Muscle aches
Bloating

When does ETEC resolve?

Onset 1-3 days

Lasts 3-4 days

How does EPEC attach and enter enterocytes?

Destroys microvilli - attaches
Type 3 mediated secretion of bacterial proteins
Tir (bacteria receptor translocated into infected cell)
Allows intimate binding

What do EPEC proteins to when translocated to cell?

Signals to reorganise host actin-cytoskeleton

Form pedestal like structures under the adherent bacteria

What does EPEC bind to?

``` Tir inserted into enterocyte Pedestal formed (anchor EPEC) EPEC binds to intimin on pedestal ```

What is shiga toxin producing e.coli? (STEC)

Verocytotoxic/enterohemorrhagic e.coli

What does STEC cause

Haemorrhagic colitis (bloody diarrhoea) Haemolytic uraemic syndrome - HUS TRIAD: Renal failure, haemolytic anaemia, thrombocytopenia

STEC first outbreak

O157:H7 Oregan/Michegan - 1982 Eating at fast food restaurant - tracked back

Molecular action of shiga toxin

B subunits bind to Gb3 Toxin endocytosed Goes to golgi and endoplasmic reticulum A chain cleaved (A1 and A2 held by disulfide bond until ER) A1 part inactivates ribosomes Inhibits protein synthesis = cell death

E.coli O157 scotland 2016

3 year old - primary case, died Dunsyre blue cheese Unpasteurised cows milk = vehicle for infection

Shiga toxin germany 2011

Contaminated bean sprouts | Women affected more than men

Extra-intestinal e.coli virulence factors

Adhesins Iron acquisition systems Protectins/invasins Toxins

UTI and e.coli who?

Common in women Anatomical differences (rectum --> urethra) Shorter distance in females

Cystitis/pyelonephritis clinical symptoms

``` Frequent and urgent urination Dysuria (burning) Suprapubic pain Nocturia Haematuria Malaise ```

Uropathogenic e-coli adhesins

Type 1 fimbrae adhesive tips | bind a-D mannosylated proteins on uroepithelium

Uropathogenic e.coli toxins

Lipopolysaccharide | a-haemolysin - cytotoxic towards epithelial cells

Uropathogenic e.coli iron acquisition

Iron is restricted in urinary tract | Bacteria produce iron-complexing proteins (siderophores) to get iron

Causes of blood stream infections

E-coli most common in england | UTI, Urinary catheters, heaptobiliary infections, GI infections

Where do blood stream infections occur UK?

50% higher in north of England BUT more common in warmer times of year (north is colder)

Emerging e.coli blood stream infections

Type 131 Type 69 - some resistant to antibiotics

Managing e-coli infections diarrhoea

Avoid contaminated foods/drink | Raw fruits and veg avoid

Treatment diarrhoea e.coli

Clear liquids - prevent dehydration Oral rehydration solution (sodium, glucose, water_ Avoid antibiotics - diarrhoea protective

Antibiotics UTI

Trimethoprim (increasing resistance or are samples to lad unrepresentative of majority?) Nitrofurantoin

Why is resistance occuring e-coli?

Bacteria so have plasmids - resistance genes can be horizontally transferred 40-50% resistant to co-amoxiclav Carbapenemase genes arising (carbapenem resistant)