Intra-abdominal infections are often polymicrobial, and include aerobic as well as anaerobic bacteria. Antibiotics used in intra-abdominal infections should aim to cover organisms such as Enterobacteriaceae and Bacteroides fragilis, which are the commonest organisms known to cause such infections. Combinations of a third-generation cephalosporin, an aminoglycoside and metronidazole are often used to treat such infections in surgical settings. An alternative to such combinations is the use of a beta lactam - beta lactamase inhibitor combination. Magnex (cefoperazone- sulbactam) is one such combination, which has been shown to be as effective as a standard multidrug regimen such as gentamicin and clindamycin in the management of intra-abdominal infections. The combination of ceftazidime, amikacin and metronidazole has been chosen as a comparator regimen because of its broad coverage of Gram-negative and anaerobic organisms found in such conditions.