Medical Microbiology and Infection

at a Glance

Fourth EditionStephen Gillespie and Kathleen Bamford

Case Studies

Case 4

A 68-year-old woman had a defunctioning colostomy performed to relieve bowel obstruction as an emergency. The procedure was complicated by faecal soiling of the peritoneum. She was prescribed broad-spectrum antibiotics postoperatively to treat faecal peritonitis.

  • 1. What local infectious complications is she at risk of developing?

    Intra-abdominal sepsis could present with generalized peritonitis or in a more localized way in the form of intra-abdominal abscesses. Abscesses could be localized to the subphrenic area, the paracolic gutter or the pelvic area. She is also at risk of developing surgical site infection.

  • 2. What organisms are likely to contribute to intra-abdominal infection?

    Organisms that make up the bowel flora will contribute. Often this will be a mixture of non-sporing anaerobes most commonly Bacteroides fragilis, together with Enterobacteriaceae such as Escherichia coli. Enterococci and Candida species may also be present.

  • 3. Describe the pathogenesis of intra-abdominal sepsis.

    Organisms of the gut flora escape the bowel into the peritoneal cavity. Facultative bacteria such as E. coli metabolise creating conditions favouring the growth of anaerobes. Toxic metabolic products, proteolytic enzymes and inflammatory components combine to extend the infection. Phagocytosis is impaired by antiphagocytic components such as the capsule of B. fragilis.

  • 4. How should intra-abdominal sepsis be treated?

    The most important component is surgical drainage of any abscess collection and debridement of devitalised tissue. Antibiotics have an important supportive role and should have activity against the Enterobacteriaceae and anaerobes.

  • 5. What other body systems are at risk of non-sporing anaerobic infection?

    The female genital tract and the oropharynx are at particular risk of non-sporing anaerobic infections. Brain, lung and liver abscesses also frequently have mixed infections. Anaerobes also colonize deep leg ulcers particularly in patients with diabetes.

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