E-coli Flashcards
Full na,e
Escherichia coli
Gram stain
Negative rods (red stain)
Microbe type
Anaerobic
Motile (flagellum)
Part of large bowel microbiota (multiple serotypes)
Family type E-coli
Enterobacteriales
What does one health ecology of ecoli mean?
Present in animals, humans and environment
Transmission can occur between these
Challenges with resistant serotypes
Ecoli under micorscope
Gram negative rods
Pile up and form colonies (from division)
(ribosome, nucleoid, plasma membrane)
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)
MacConkey Agar e-coli result
Lactose fermenting so stains PINK
How are different e-coli’s typed?
Serology (antibodies and antigens)
Metabolic profiling
Genomic diversity (whole genome sequencing, DNA hybridisation)
Antigens present on e-coli
K - capsule
O - lipopolysaccharide wall
F - fimbriae
H - flagella
(KOFH)
Genetic diversity of e-coli
IMMENSE
E-coli function large bowel
Large bowel microbiota (humans & animals)
Protects against invasion of pathogenic species (salmonella)
What can e-coli cause?
Intestinal infections (diarrhoea)
Extra-intestinal infections: UTI Biliary tract Intra-abdominal abscess Blood stream infection
NEONATAL MENINGITIS
What determines pathology of e-coli?
Presence of virulence factors on specific e-coli strains
How does e-coli invade?
Different ways depending on subtype/strain
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)
Most common diarrhoea e.coli children of developing world
Enteropathogenic
Enteroinvasive
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)
