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Health condition · Clinically reviewed

E. coli, from urinary tract infection to STEC diarrhoea and HUS.

A normal gut inhabitant with several very different faces. Knowing which strain you are dealing with changes the treatment plan, sometimes dramatically.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE, UKHSA and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK guidance on STEC/O157 management, HUS care and resistance-aware antibiotic use.

Key facts

E. coli at a glance.

The essentials, in plain English. What E. coli is, which strains matter, and how UK clinicians approach diagnosis and treatment today.

  • What it is

    Escherichia coli, a Gram-negative bacillus. A normal gut inhabitant, but several pathogenic strains cause significant disease.

  • Common UTI cause

    Uropathogenic E. coli (UPEC) is the most common cause of urinary tract infection and pyelonephritis in the UK.

  • Diarrhoeal strains

    ETEC, EPEC, EIEC, EAEC and Shiga toxin-producing STEC/EHEC (including O157:H7) each cause different diarrhoeal syndromes.

  • HUS risk

    STEC infection can trigger haemolytic uraemic syndrome (HUS), a leading cause of paediatric acute kidney injury.

  • Notifiable

    E. coli O157 and STEC are UKHSA notifiable. Suspected cases need statutory reporting and public-health follow-up.

  • Resistance rising

    ESBL and carbapenem-resistant E. coli are increasingly common, so culture-guided therapy matters more than ever.

Why this guide matters

One bug, several very different plans.

Getting the strain right, and the site of infection right, is what separates safe care from a serious mistake.

  • Culture-guided antibiotics

    Resistance is rising. Local sensitivities and culture results should shape antibiotic choice, especially for UTI, sepsis and complicated infection.

  • STEC needs restraint

    Bloody diarrhoea from Shiga toxin-producing E. coli is treated with careful supportive care. Antibiotics and loperamide raise the risk of HUS.

  • HUS is a paediatric emergency

    Pallor, oliguria and petechiae after diarrhoeal illness need urgent specialist renal and intensive care assessment.

How the diagnosis is made

From first symptoms to a clear plan.

The steps a UK GP, hospital doctor or paediatrician will normally follow, so you know what to expect and why.

  1. 01

    Assessing

    History and exposure review

    Recent travel, undercooked meat, unpasteurised dairy, salad, contaminated water, petting farms and contact with reptiles or unwell children.

  2. 02

    Assessing

    Clinical assessment

    Urinary symptoms, watery or bloody diarrhoea, systemic sepsis signs, hydration status and abdominal examination.

  3. 03

    Assessing

    Urine culture

    For suspected UTI or pyelonephritis, with sensitivities to guide antibiotic choice.

  4. 04

    Confirming

    Stool culture and PCR

    For diarrhoea, specifically request STEC/O157 screening and Shiga toxin testing when bloody stool is present.

  5. 05

    Confirming

    Blood cultures if systemic

    For bacteraemia, sepsis, urosepsis or cholangitis. E. coli bacteraemia is subject to mandatory UKHSA surveillance.

  6. 06

    Confirming

    HUS bloods when STEC suspected

    FBC, U&Es, LDH, haptoglobin, reticulocytes and a blood film for microangiopathic haemolytic anaemia, thrombocytopenia and acute kidney injury.

  7. 07

    Public health

    Imaging and public-health steps

    Ultrasound or CT for complicated urinary or intra-abdominal disease. UKHSA notification for O157 and STEC with contact tracing.

Typical timeline: from first stool or urine sample to a working diagnosis in 24 to 72 hours.

Symptoms

What E. coli actually looks like.

Urinary, gastrointestinal and systemic patterns, plus the features that mean it is time to seek urgent care.

  • Urinary symptoms

    Dysuria, frequency, urgency, suprapubic pain and sometimes visible haematuria. Most often driven by uropathogenic E. coli.

  • Watery diarrhoea

    Typical of ETEC (traveller’s diarrhoea) and EPEC. Usually self-limiting with careful rehydration.

  • Bloody diarrhoea

    A hallmark of STEC/EHEC, including O157:H7. Needs stool testing for Shiga toxin and cautious, non-antibiotic supportive care.

  • Persistent diarrhoea

    Enteroaggregative E. coli (EAEC) can cause prolonged watery diarrhoea, especially after travel or in immunocompromise.

  • Dysentery-like illness

    Enteroinvasive E. coli (EIEC) mimics Shigella with fever, cramps and bloody mucoid stools.

  • Sepsis and bacteraemia

    Fever, rigors, hypotension and confusion, often from a urinary or intra-abdominal source. E. coli is a leading cause of Gram-negative sepsis.

  • HUS features

    Pallor, oliguria, petechiae and reduced urine output 5 to 10 days after bloody diarrhoea. A paediatric emergency.

  • Red flag – neonatal illness

    Neonatal sepsis and meningitis can be caused by extraintestinal E. coli and need urgent hospital assessment.

Treatment

How E. coli infection is treated in the UK.

The right treatment depends on the strain and the site. From simple UTIs and traveller’s diarrhoea to sepsis, HUS and resistant strains.

  • Uncomplicated UTI

    Nitrofurantoin, trimethoprim, cefalexin or fosfomycin guided by local sensitivities. See our cystitis guide for detail.

  • Pyelonephritis

    Ciprofloxacin, co-amoxiclav or gentamicin, refined once cultures return. Admission for systemic illness, pregnancy or failure to improve.

  • Bacteraemia and sepsis

    Broad-spectrum IV therapy such as piperacillin-tazobactam or a carbapenem, plus source control and culture-guided de-escalation.

  • STEC and O157 diarrhoea

    Supportive care with careful IV fluids. Avoid antibiotics and antimotility agents such as loperamide, both increase HUS risk.

  • Haemolytic uraemic syndrome

    Specialist renal and intensive care with haemodialysis, transfusion and selective plasma exchange. Eculizumab in atypical or severe cases.

  • Traveller’s diarrhoea

    Usually self-limiting with rehydration. Short-course azithromycin or rifaximin for severe or persistent illness.

  • Resistant strains (ESBL, CRE)

    Specialist microbiology input, narrow-spectrum where possible and carbapenem-sparing strategies. Colistin reserved for last-line use.

  • Prevention

    Hand hygiene, food safety, water treatment, careful catheter use and public-health control at petting farms and outbreak settings.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP or hospital clinician knows your history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Urinary tract infection (lower and upper): antimicrobial prescribing guidance.

  • UK Health Security Agency (UKHSA). Public health operational guidelines for STEC and E. coli O157.

  • UKHSA. Mandatory surveillance of Gram-negative bacteraemia (including E. coli).

  • British Society for Antimicrobial Chemotherapy (BSAC) and European guidance on ESBL and carbapenem-resistant Enterobacterales.

Red flags

When E. coli needs urgent attention.

Most cases are managed in primary care. These are the situations that are not, and where hospital or specialist input is needed.

  • Bloody diarrhoea

    Send stool for STEC and Shiga toxin testing, avoid antibiotics and antimotility agents until cleared, and watch closely for HUS.

  • Suspected HUS

    Pallor, bruising, reduced urine output and drowsiness after diarrhoeal illness. Urgent hospital and paediatric renal assessment.

  • Sepsis or urosepsis

    Fever, rigors, hypotension, confusion or reduced urine output. Sepsis-six pathway and IV antibiotics without delay.

  • Pregnancy with UTI

    Even mild symptoms deserve prompt culture-guided treatment because of pyelonephritis and pre-term labour risk.

  • Neonatal fever or lethargy

    E. coli is a leading cause of neonatal sepsis and meningitis. Any unwell newborn needs same-day hospital assessment.

  • Immunocompromise

    Chemotherapy, transplant or advanced liver disease change the threshold for admission and broad-spectrum cover.

  • Outbreak setting

    Clusters at nurseries, farms, care homes or after shared meals warrant UKHSA notification and contact tracing.

  • Recurrent or resistant UTI

    Multiple resistant isolates or repeated infection warrant renal imaging, specialist urology and stewardship review.

  • Ascending cholangitis

    Fever, jaundice and right upper quadrant pain point to biliary sepsis and need urgent imaging and drainage.

Living with it

Recovery, and staying well.

Four practical habits that reduce reinfection, protect the people around you and keep future antibiotic choices open.

A quiet reminder

Simple habits, done consistently, make the biggest difference.

Careful handwashing, safe food preparation and finishing prescribed antibiotics do more than any single new intervention.

  1. 01 Hydration

    Fluids first, always

    For diarrhoea and UTI alike, steady oral rehydration is the single most useful thing you can do at home.

  2. 02 Kitchen

    Food and water safety

    Cook meat thoroughly, avoid unpasteurised dairy, wash salad well and be cautious with untreated water when travelling.

  3. 03 Hygiene

    Hand washing that actually works

    Soap and warm water after the toilet, before food and after contact with animals or nappies. Alcohol gel alone is not enough against STEC.

  4. 04 Follow up

    Finish the plan

    Complete culture-guided antibiotics as prescribed and return for review if symptoms persist, worsen or recur.

Frequently asked

Everything we get asked about E. coli.

Quick answers on UTI, STEC/O157, HUS, resistance and how to stay safe at home and abroad.

  • What is E. coli?

    Escherichia coli is a Gram-negative bacterium that lives harmlessly in the human gut. Some strains, however, cause urinary tract infection, sepsis, diarrhoea and, in the case of Shiga toxin-producing strains, life-threatening haemolytic uraemic syndrome.

  • Why should antibiotics be avoided in E. coli O157 diarrhoea?

    Antibiotics and antimotility drugs such as loperamide are associated with a higher risk of haemolytic uraemic syndrome in STEC infection, probably because they increase Shiga toxin release. UK guidance is to treat with careful supportive care instead.

  • How do people catch STEC and O157?

    Common sources include undercooked beef, unpasteurised milk or cheese, contaminated leafy salad, untreated water, and direct contact with animals at farms or petting zoos. Person-to-person spread also occurs in nurseries and households.

  • Is E. coli UTI serious?

    Uncomplicated cystitis is very treatable with a short course of the right antibiotic. Pyelonephritis, urosepsis and infections during pregnancy or in older adults are more serious and often need hospital care.

  • What is haemolytic uraemic syndrome (HUS)?

    HUS is a triad of microangiopathic haemolytic anaemia, thrombocytopenia and acute kidney injury that typically follows STEC diarrhoea by 5 to 10 days. It is a leading cause of acute kidney injury in children and needs urgent specialist care, sometimes including dialysis and eculizumab.

  • Is there a vaccine for E. coli?

    No E. coli vaccine is currently licensed for routine use in the UK, although candidates are in trials. Prevention rests on hand hygiene, food and water safety, careful catheter care and, in healthcare, robust infection control.

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