For an overview of the treatment of intra-abdominal / biliary tract / peritonitis see below:
N.B. Review total (IV and oral) duration after 4 days if source control achieved.
Intra-abdominal infections are usually polymicrobial.
Amoxicillin provides cover for streptococci of the group formerly known as "Strep milleri", which are always amoxicillin susceptible and for enterococci (amoxicillin resistance rates <10%). It provides no reliable cover for E. coli (70% of bloodstream isolates are resistant). Klebsiella species are always amoxicillin resistant.
Gentamicin provides reliable cover for gut-associated gram negative infections. Resistance rates in enterobacteriaceae from abdominal sampling are around 8%, compared with 75% resistance against amoxicillin and 50% resistance against co-amoxiclav. If the use of gentamicin is contraindicated, the agent should not simply be omitted, but an alternative regimen should be chosen. Gentamicin should be reviewed after 72 hours, due to the risk of ototoxicity associated with prolonged use. See the 'IV Gentamicin Review after 72 hours of Treatment' algorithm (N.B. links within the document are only active if accessing via NHS network).
Gentamicin must not be administered to patients with myasthenia gravis as it can precipitate a myasthenic crisis.
Metronidazole provides only anaerobic cover. Enterobacteriaceae like E. coli are inherently resistant.
The majority of clinically significant fungal isolates from abdominal infections are C. albicans, which is fluconazole susceptible.
Page last updated: February 2024