Lecture 17 - Escherichia Coli Flashcards
How can E.coli be described?
Gram-negative rods
Typically lactose fermenting
Often motile
What colour does Escherichia coli stain with gram stain?
What type of bacteria are they?
Red/pink
Gram-negative rods
Where are E.coli usually found?
In large bowel of animals + humans
What family does E.coli belong to?
Enterobacteriaceae
What family does E.coli belong to?
Enterobacteriaceae
How can E.coli and other Enterobacteriaceae be differentiated from other bacteria like Pseudomonas aeruginosa?
E.coli = can use lactose as an energy source making lactic acid as waste (with pH indicator = pink/red)
Pseudomonas aeruginosa = non lactose fermenting (can use lactose) with pH indicator = yellow
What are the different ways by which different species of E.coli can be identified?
Serology (use antibodies to detect different bacterial surface antigens)
Metabolic profiling
Genomic diversity
How is E.coli typically transmitted?
Faecal-oral route:
-Faeces used as fertiliser for crops, crops not washed
-from animals to humans
What are the 4 different serological antigens of E.coli which can be identified by serological antibodies?
O - LPS (Lipopolysaccharide membrane)
H - Flagella
K - Capsule
F- Fimbriae
Where is E.coli considered normal flora?
Large bowel
What is E.coli’s role in the large intestine?
Protects against invasion by pathogenic species like Salmonella
What diseases can be caused as a result of E.coli?
Intestinal infections (diarrhoea)
Toxin-mediated disease
Extra—intestinal infections
What are some examples of extra-intestinal infections that E.coli can cause
UTI
Intra-abdominal
Biliary tract
Bloodstream infection
Neonatal meningitis
How many pathotypes of E.coli are there that cause diarrhoea?
6
What are the 6 pathotypes of diarrhoeagenic E.coli?
Enterotoxigenic E.coli (ETEC)
Enteropathogenic E.coli (EPEC)
Enteroaggregative E.coli (EAEC)
Enteroinvasive E.coli (EIEC)
Diffusely adherent E.coli (DAEC)
Shiva toxin-producing E.coli (STEC)
How does E.coli generally cause diarrhoea?
Adheres to the gut epithelia damaging them causing it to become inflamed, leading to diarrhoea
What does ETEC stand for?
Enterotoxigenic E.coli
What does STEC stand for?
Shiga toxin-producing E.coli
Why can STEC be know as Verocytotoxic E.coli (VTEC)?
Damages vero cells
Why can shiga toxin-producing E.coli be know as Enterohemorrhagic E.coli (EHEC)?
Can cause Haemorrhagic colitis (Bloody diarrhoea) and haemolytic uraemia syndrome
What is Haemolytic uraemia syndrome (HUS)?
Triad of:
-acute renal failure
-haemolytic anaemia
-thrombocytopenia
How does Shiga toxin produce symptoms/cause damage?
Toxin binds to Gb3 on cell
Toxin endocytosed into cell
Transported to Golgi
Fragments of toxin cleaved
Harmful fragment released into cytosol
Inactivates ribosomes inhibiting protein synthesis
How does shiga toxin basically cause cell damage/damage large intestinal lining?
Toxin inhibits protein synthesis in cell
What treatment does a patient need with Haemolytic Uraemic syndrome and why?
Dialysis to treat the acute renal failure
What are extra intestinal pathogenic E.coli (ExPEC)?
Strains of E.coli capable of causing disease outside the intestinal tract
Have a wide range of virulence factors
What is Cystitis?
Urinary tract infection often caused by E.coli
Why are UTIs more common in women?
Anatomical differences
Much shorter journey for women from faeces
How does Cystitis lead to Pyelonephritits?
Cystitis where the E.coli travels up the ureters to the kidneys
What is the most common cause of bacterial bloodstream infection?
E.coli
What are some causal factors for E.coli bloodstream infections (E.coli bacteraemia)?
Age
Hepatobiliary infections
UTIs
Catheterised patients
GI infections
How are Diarrhogenic E.coli infections prevented?
Avoid foods and drink that could be contaminated
How are Diarrhogenic E.coli infections treated?
Most infected recover in a few days
Clear liquids (prevent dehydration and loss of electrolytes)
Oral rehydration solutions
Avoid antibiotics (may make illness worse)
What needs to be avoided when treating Diarrhogenic E.coli infections?
Antibiotics (AVOID)
How are UTIs treated?
Antibiotics
What antibiotics are used to treat Urinary Tract Infections (UTI)?
Trimethoprim (treatment can fail if UTI is resistant to this)
Nitrofurantoin
What strain of E.coli causes travellers diarrhoea?
Enterotoxigenic E.coli (ETEC)
By producing 2 toxins
What is febrile neutropenia?
Fevers that coincide with low neutrophils
What is the first line treatment for febrile neutropenia?
IV Tazocin (Piperacillin + Tazobactam) 4.5g TDS
If penicillin allergic - IV meropenem 1g TDS
What do you add to treat febrile neutropenia if there evidence of infection of the Hickman line?
IV vancomycin
What type of organisms does Tazocin (Piperacillin and Tazobactam) target?
Gram +ve and -ve
What type of organisms. Does vancomycin target?
Gram +ve
