STEC infection in adults | Right Decisions

Diagnostic considerations

Differential diagnosis: In adults, bloody diarrhoea can have various causes, including:

infectious (Campylobacter, Shigella, Salmonella, STEC)
non-infectious (inflammatory bowel disease, diverticular disease, ischaemic colitis, malignancy).

STEC as a cause: While uncommon in adults, STEC should be considered because of the risk of HUS and its high mortality,^4,45,46 and public health risk, as around 20% of cases have occurred in outbreaks.¹⁸

Initial assessment (primary or secondary care)

Suspect STEC in adults with:

acute bloody diarrhoea
non-bloody diarrhoea with risk factors.

Follow the flowchart for management of acute bloody diarrhoea or clinically suspected STEC infection in adults.

Assess for:

dehydration
severe illness features, eg frequent bloody diarrhoea, severe abdominal pain, vomiting, pallor, petechiae, oliguria, blood and protein on urine dipstick^7,19,20,21
epidemiological risk factors
alternative diagnoses (especially requiring surgery).

If STEC is suspected, discuss the case urgently with an infection specialist.

Initial management in primary care

If STEC is suspected based on clinical features or risk factors:

Stool sample: urgently send a stool sample for culture, notifying the laboratory of urgency.
Provide relevant clinical history, particularly any history of bloody diarrhoea, on the stool culture request.
As well as details of bloody diarrhoea, other relevant clinical history should be included on the form e.g. HUS, contact with case, part of an outbreak investigation.
If clinical history is suggestive of STEC (bloody diarrhoea, HUS, contact with a case), carry out PCR testing to detect Shiga toxin (stx) genes.
If HUS is indicated, diagnostic laboratories should refer stool samples to SERL on the day of receipt or next business day, pending local culture.

If STEC is suspected or confirmed:

Hospitalisation: Refer people with severe illness, dehydration or suspected complications for admission.
Further investigation: Test blood and urine to look for dehydration or HUS.
Public health notification: notify the local public health team immediately, even before test results.

Additional considerations

Advise the household contacts on hygiene and control measures (cleaning, food handling). A patient information leaflet is available to download and public health can provide further support.
Manage any close contacts with diarrhoea promptly as suspected cases of STEC.
Advise symptomatic people to remain away from school and work for at least 48 hours after symptom resolution.
High-risk groups (food handlers, people working with vulnerable groups and high-risk groups in the same household as an infected person) will require longer exclusion and guidance from public health.¹

Public health will contact the person to investigate the infection source and provide advice on preventing spread and returning to childcare, school and work.

Adults managed at home should be provided with information on:

rehydration
symptoms that indicate concern
the expected clinical course of their illness
good personal hygiene to reduce the risk of transmission in household contacts
how to get immediate help from appropriate healthcare professionals should their symptoms worsen or fail to settle.

Disease progression to HUS

Less than 5% of adults with STEC infection develop HUS⁴⁷

Risk factors: Older age and comorbidities increase the risk of HUS in adults. HUS in adults, particularly older adults, carries a significant mortality risk (up to 30%)¹⁰ and can lead to long-term kidney complications.

Clinical presentation: HUS can present with renal dysfunction, neurological symptoms and other organ involvement.

Timing of HUS onset: Typically, 6-8 days after the onset of diarrhoea, but it can occur up to 14 days after the initial infection,^18,22 and even after apparent recovery.¹³

Management in secondary care

Assessment and monitoring:

Assess and monitor for dehydration.
Order blood and urine tests to assess for dehydration and potential HUS (as recommended in Table 2).
Stool sample: If STEC is not confirmed, urgently send a stool sample for culture, notifying the laboratory of urgency.
Provide clinical history, particularly details of bloody diarrhoea, and other relevant clinical history e.g. HUS, contact with case, part of an outbreak investigation, on the stool culture request.
If clinical history is suggestive of STEC (bloody diarrhoea, HUS, contact with a case or outbreak), undertake PCR testing for both E. coli O157 and non-O157 STEC.
If a local PCR is positive, but local culture is unsuccessful, the stool should be referred to SERL.
If a local PCR is negative, but the patient is presenting with HUS or acute bloody diarrhoea and is causing clinical concern, discuss referral of stools for further testing with SERL.
Implement mandatory infection-control measures immediately.

Intravenous fluid therapy

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Start early intravenous fluid therapy in adults with suspected STEC infection who:

are unwell
are dehydrated
have high-risk clinical features of HUS
have laboratory features suggestive of HUS

Use isotonic intravenous solution (0.9 % sodium chloride or PlasmaLyte), depending on electrolytes, for fluid deficit replacement and maintenance.

Monitor fluid balance carefully. Discuss further management with nephrology services if there is concern of fluid overload or developing HUS.

Public health and patient education

Notify the local public health team immediately, even before test results are available.
Advise household contacts on hygiene, environmental cleaning and food handling practices. Public health can provide further support.
Inform patients that public health will contact them to investigate the infection source, prevent spread and guide school or work return.
Continue investigating and managing other causes of colitis while awaiting a definitive diagnosis.

Symptom management and medication

Symptom management:

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Antimotility agents are not recommended for treating diarrhoea because of the potential association with developing HUS.^4,11
Simple analgesics are preferred for pain management. Opiates should be avoided if possible.^26,27 In cases of severe pain, opiate use may be necessary, but surgical assessment (including abdominal imaging) should be considered.

NSAIDs should be avoided because of potential adverse effects on renal blood flow and increased risk of kidney injury.²⁸

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Antibiotics are not recommended. Antibiotic treatment, especially bactericidal antibiotics like beta-lactams, may increase the risk of HUS.^{7,19,20,25,30,31,32, 33}

Clinical judgement: Antibiotic use should be limited to specific clinical indications unrelated to STEC infection and discussed with an infection specialist.

Monitoring for HUS in adults with STEC infection

Postinfection monitoring:

14-day follow-up: Adults with confirmed STEC infection should be monitored for at least 14 days after the onset of diarrhoea to detect potential HUS.
Clinical review: Adults confirmed to be STEC positive, who are well should have ongoing review until 14 days after the onset of diarrhoea.
Urine testing: Daily urine dipstick testing for blood and protein for 14 days.
Blood tests: Repeat blood tests if clinical deterioration occurs.
Medical referral: Refer for hospital admission if clinical features of concern develop. Consult with a nephrologist for suspected or confirmed HUS.

Management of confirmed HUS

Nephrology referral: Adults with HUS should be managed by a nephrologist.
Renal replacement therapy: Approximately 50% of adult patients with HUS require dialysis.^43,44
Long-term outcomes: While most adults recover kidney function, there is a risk of long-term renal and other complications, like hypertension.^37,38,39
There is currently insufficient evidence to recommend plasma exchange for STEC-associated HUS.

Supportive care: Supportive therapy, including fluid and electrolyte balance, dialysis where indicated and blood pressure control, remains the preferred treatment.^39,40
Plasma Exchange: There is currently insufficient evidence to recommend plasma exchange for STEC-associated HUS.^39,40
Eculizumab: While eculizumab was used in the 2011 European E. coli outbreak, the results were mixed, with no definitive positive effect on clinical outcomes from eculizumab reported.^42,43,44,45Eculizumab therapy was often given when there was severe neurological involvement or persistence of HUS despite plasmapheresis therapy. There was some evidence that in patients with typical HUS and CNS involvement, early use of eculizumab was associated with good neurological outcome, but in patients with rapidly progressing HUS and multiple organ involvement, eculizumab seemed to be less beneficial.

Information for adults with clinically suspected or confirmed STEC infection

Give patients the STEC Patient Information Leaflet. Advise the patient to seek immediate medical attention if experiencing any of these symptoms:

bloody diarrhoea (if new)
repeated vomiting
severe abdominal pain or cramps
decreased urination or smaller urine amounts
increased weakness or fatigue
cold hands and feet
pale appearance
petechiae (small red or purple spots on skin)
swelling (especially around eyes, legs or feet)
headache.

Provide emergency healthcare contact details.