Appropriate antibiotic choices for managing peritonitis in a community setting depend on the suspected cause and severity of infection, but generally involve broad-spectrum antibiotics covering aerobic and anaerobic bacteria.
For suspected or confirmed complicated intra-abdominal infections such as peritonitis related to diverticulitis, oral antibiotic options in the community include co-amoxiclav 500/125 mg three times daily for 5 days as first choice.
If penicillin allergy or co-amoxiclav is unsuitable, alternatives include cefalexin (500 mg two or three times daily) plus metronidazole (400 mg three times daily), or trimethoprim (200 mg twice daily) plus metronidazole (400 mg three times daily), all for 5 days.
Oral ciprofloxacin with metronidazole may be used only if switching from intravenous ciprofloxacin with specialist advice and when other antibiotics are inappropriate, due to risks of disabling side effects.
People who are systemically unwell or immunosuppressed should be considered for antibiotic therapy, but those with complicated peritonitis or severe infection require hospital assessment and intravenous antibiotics.
In summary, in the community setting, oral co-amoxiclav is the first-line antibiotic for peritonitis related to diverticulitis, with alternatives as above, and hospital referral is indicated for complicated or severe cases.
These recommendations align with NICE guidance on diverticular disease and antimicrobial stewardship principles.
References: NICE NG147, NICE CKS