Anaerobic Infections, Intra-Abdominal

Key Features

• Each gram of stool contains up to 10¹¹ anaerobes, predominantly

  • Bacteroides fragilis

  • Clostridia

  • Peptostreptococci

• These organisms play a central role in most intra-abdominal abscesses after trauma to the colon and in

  • Diverticulitis

  • Appendicitis

  • Perirectal abscess

• They may also participate in hepatic abscess and cholecystitis

• The bacteriology of these infections includes anaerobes as well as enteric gram-negative rods and, on occasion, enterococci

Clinical Findings

• Related to infected organ

Diagnosis

• Examination, laboratory tests, cultures, and CT scan

Treatment

• Therapy should be directed both against anaerobes and gram-negative aerobes

• Antibiotics that are reliably active against B fragilis include

  • Metronidazole

  • Moxifloxacin

  • Tigecycline

  • Chloramphenicol

  • Carbapenems (ertapenem, imipenem, meropenem)

  • Ampicillin-sulbactam

  • Ticarcillin-clavulanic acid

  • Piperacillin-tazobactam

• Resistance to cefoxitin, cefotetan, and clindamycin is increasingly encountered

• Table 33–6 summarizes the antibiotic regimens for management of

  • Moderate to moderately severe infections (eg, patient hemodynamically stable, good surgical drainage possible or established, low APACHE score, no multiple-organ failure)

  • Severe infections (eg, major peritoneal soilage, large or multiple abscesses, patient hemodynamically unstable), particularly if drug-resistant organisms are suspected