Summary of antimicrobial guidance

Please refer to the user guide and principles of treatment when using the antimicrobial prescribing guidance summaries.

Contents

Clostridioides difficile infection

For suspected or confirmed C. difficile infection, see UK Health Security Agency’s guidance on diagnosis and reporting.

Assess: whether it is a first or further episode, severity of infection, individual risk factors for complications or recurrence (such as age, frailty, or comorbidities).

Existing antibiotics: review and stop unless essential. If still essential, consider changing to one with a lower risk of C. difficile infection.

Review the need to continue: proton pump inhibitors, other medicines with gastrointestinal activity or adverse effects (such as laxatives), medicines that may cause problems if people are dehydrated (such as NSAIDs).

Do not offer antimotility medicines such as loperamide.

Offer an oral antibiotic to treat suspected or confirmed C. difficile infection.

For adults, consider seeking prompt specialist advice from a microbiologist or infectious diseases specialist before starting treatment.

For children and young people, treatment should be started by, or after advice from, a microbiologist, paediatric infectious diseases specialist or paediatric gastroenterologist.

If antibiotics have been started for suspected C. difficile infection, and subsequent stool sample tests do not confirm infection, consider stopping these antibiotics.

Adult first-line for first episode of mild, moderate, or severe: 

vancomycin 125mg QDS for 10 days

Adult second-line for first episode of mild, moderate, or severe if vancomycin ineffective: 

fidaxomicin 200mg BD for 10 days

For further episode in an adult within 12 weeks of symptom resolution (relapse): 

fidaxomicin 200mg BD for 10 days

For further episode in an adult more than 12 weeks after symptom resolution (recurrence): 

vancomycin 125mg QDS for 10 days

OR

fidaxomicin 200mg BD for 10 days

For alternative antibiotics if first- and second-line antibiotics are ineffective or for life-threatening infection: seek specialist advice (see the guidance visual summary)

For information on children’s dosage or for detailed information see the guidance visual summary or https://www.nice.org.uk/guidance/ng199

NICE

Section last updated July 2021

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Acute Diverticulitis

Acute diverticulitis and systemically well: Consider no antibiotics, offer simple analgesia (for example paracetamol), advise to re-present if symptoms persist or worsen.

Acute diverticulitis and systemically unwell, immunosuppressed, or significant comorbidity: offer an antibiotic.

Give oral antibiotics if person not referred to hospital for suspected complicated acute diverticulitis.

Give IV antibiotics if admitted to hospital with suspected or confirmed complicated acute diverticulitis (including diverticular abscess).

If CT-confirmed uncomplicated acute diverticulitis, review the need for antibiotics.

First-choice for adults (uncomplicated acute diverticulitis): 

co-amoxiclav 500/125mg TDS for 5 days (a longer course may be needed based on clinical assessment)

Penicillin allergy for adults or if co-amoxiclav unsuitable: 

cefalexin (caution in penicillin allergy) 500mg BD or TDS (up to 1g to 1.5g TDS or QDS for severe infections) AND  metronidazole 400mg TDS for 5 days (a longer course may be needed based on clinical assessment)

OR

trimethoprim 200mg BD WITH metronidazole 400mg TDS for 5 days (a longer course may be needed based on clinical assessment)

OR

Ciprofloxacin (only if switching from IV ciprofloxacin with specialist advice) 500mg BD WITH metronidazole 400mg TDS for 5 days (a longer course may be needed based on clinical assessment)

See the MHRA January 2024 advice for restrictions and precautions on using fluoroquinolone antibiotics because of the risk of disabling and potentially long-lasting or irreversible side effects. Fluoroquinolones must now only be prescribed when other commonly recommended antibiotics are inappropriate

For IV antibiotics in complicated acute diverticulitis (including diverticular abscess): see visual summary or NICE guidance

For information on children’s dosage or for detailed information see the guidance visual summary or https://www.nice.org.uk/guidance/NG147

NICE

Section last updated September 2024