E. coli

What is the full name of E. coli?

Escherichia coli

Where is E. coli commonly found?

intestines of many animals (especially mammals)

What diseases can be caused by pathogenic E. coli (4)?

• UTI’s

• bloodstream infections

• meningitis

• gastrointestinal disease

What are the majority of E. coli isolates?

commensals

How many extra base pairs are observed in pathogenic E. coli O157:H7 compared to a commensal strain ()?

• 1.3 million extra base pairs

• extensive variation even within a species

What type of genome does E. coli have?

‘open’ genome

What are the aims of PATH-SAFE (4)?

• pathogen surveillance in agriculture, food and environment

• better national surveillance system

• monitor and track foodborne disease

• AND antimicrobial resistance

Where does most high level E. coli resistance emerge?

clinical settings (MDR strains can emerge)

Why is wastewater sampled for E.coli strains?

allows random sampling of the healthy population

How can E.coli genomes be used to find out the host species (3)?

• phylogeny based (SNP address)

• genome data (gene presence / absence)

• machine learning (AI / models)

How does machine learning work to discover source attribution (the host of a particular E. coli strain) (4)?

• analyses relationships between provided information

• probabilistic assignment (confidence score)

• isolates run through many single-host models

• assignment based on confidence score for host being above threshold

What are the basic characteristics that define the different E.coli pathotypes (5)?

• toxins

• adherence mechanisms

• antigens (LPS, flagella, fimbriae and capsules)

• anabolic and catabolic requirements

• gene expression variation

Why is regulation of virulence factors important (2)?

• express appropriate genes for the environment

• not all genes expressed at same time (wasteful)

How does uropathogenic E.coli (UPEC) adhere to its target cells (2)?

• type 1 and P fimbriae

• vis their FimH and PapG tip adhesins

Which toxins can be released by uropathogenic E.coli (UPEC) (2)?

• haemolysins

• cytotoxic necrotising factor (CNF)

What is the purpose of releasing toxins?

release nutrients for usage

How can uropathogenic E.coli (UPEC) cause recurrent infections?

forms transient intracellular bacterial communities

What bacteria is the leading cause of human UTIs (2)?

• uropathogenic E.coli (UPEC)

• colonises the urinary tract

What was observed in CFT073, a uropathogenic E.coli (UPEC) isolate?

multiple fimbrial operons (to bind to different targets)

What is phase variation (2)?

• low level, random expression limits co-expression

• different molecular subsets being expressed within same population

What is sequential expression?

one gene expressed before another

What mediates adherence in Enterohaemorrhagic E.coli (EHEC) (2)?

• haemorrhagic coli pilus (HCP)

• flagella

How does Enterohaemorrhagic E.coli (EHEC) cause haemorrhagic colitis and kidney failure?

shiga-toxin (Stx) release

How is Enterohaemorrhagic E.coli (EHEC) defined ()?

possession of…

• type 3 secretion system

• AND shiga-toxin (Stx)

What does Enterohaemorrhagic E.coli (EHEC) use its type 3 secretion system for?

generate attaching and effacing (A / E) lesions

What are the primary hosts of Enterohaemorrhagic E.coli (EHEC)?

ruminants (humans are incidental hosts)

What do the ‘O’ and ‘H’ mean in Enterohaemorrhagic E.coli O157 : H7?

• O157 = 157th O-antigen (LPS)

• H7 = 7th H-antigen (flagella)

How are STEC defined?

E.coli isolates with Stx (shiga-toxin) encoding phages integrated into their genomes as prophages

What are prophages (as observed in STEC)?

short-tailed lambda-like bacteriophages that encode different types of shiga-toxin (Stx)

What is the result of Enterohaemorrhagic E.coli (EHEC) infection in humans (2)?

• 10% = bloody diarrhoea (result of acute gastroenteritis)

• 5% = capillary damage in eyes and brain

Where is STEC O157 : H7 most common (a type of Enterohaemorrhagic E.coli (EHEC)) ?

developed countries

Why do cattle not experience the same serious symptoms as humans when infected by Enterohaemorrhagic E.coli (EHEC)?

shiga-toxin receptor is on different cells (evolved for different purpose in cattle)

How does shiga-toxin cause disease (5)?

• released upon bacterial cell lysis

• acts on sensitive cells (in humans = blood vessels)

• damages endothelial cells

• blocks protein synthesis and cell dies

• host response key to pathology

What cells does shiga-toxin mainly act on in humans?

endothelial cells

What are some alternative infection routes for shiga-toxigenic E.coli (STEC) (2)?

• leafy greens and raw / low processed foods (e.g. unpasteurised cheese)

• petting zoo / open farms

What strain caused an outbreak in Germany in 2011 (3)?

• hybrid strain

• STEC + EAEC = Stx-EAEC

• shigatoxin phage transfer to strain better at colonising humans

What is the Stx-EAEC strain?

• STEC strain (shiga toxin producing) crossed with

• enteroaggregative E. coli (EAEC)

What evidence exists for the role of the type 3 secretion system in E.coli?

K/O = cannot colonise cattle

Where does EHEC O157 : H7 colonise cattle?

exclusively at rectum (ring of infection - niche)

What strain does Scotland have a problem with and why is this an issue (2)?

• Stx2a/2c+

• associated with severe disease in humans

What is the role of shiga toxin in cattle (3)?

• acts on base of crypts in cow intestine

• limits gut turnover = promotes colonisation

• bacteria not shed as easily

What are 3 interventions that have been trialled to try and prevent E.coli O157 in cattle (and so hopefully reduce human cases) (2)?

• vaccine against type 3 secretion system

• phage therapy (idea was to put in feed)