Antibiotic therapy in intra-abdominal infections--a review on randomised clinical trials

There have been 79 randomised antibiotic studies in intra-abdominal infections retrieved. The overall success rate of the studied antibiotics ranges from 70-100%. Unfortunately only about one fourth of the studies have used a disease severity classification, e.g., APACHE II score, despite clear recommendations by the Surgical Infections Society of North America. The mortality rate in the published antibiotic studies is still rather low (approximately 4%) and does not correspond to the average mortality in peritonitis (30-40%). Failure analysis is not uniform and only performed in about 1/5 of retrieved studies. Failure analysis included data on diagnosis, type of operation, pathogen isolated at first operation, susceptibility and persistence of pathogen, re-operation or change of antibiotic regimen, and follow-up (ICU duration, death or survival, hospitalisation). Only one study has performed an analysis of the adequacy of the surgical treatment (source control). The clinical success rate of the antibiotics studied in a larger population is comparable for gentamicin + clindamycin (80%), tobramycin + clindamycin (83%), meropenem (89%), imipenem (85%), aztreonam + clindamycin (89%), cefoxitin (88%), cefotetan (92%), moxalactam (83%), cefotaxime + metronidazole (87%), ampicillin/sulbactam (87%). Piperacillin/tazobactam has in most studies a success rate of approximately 90%. The aggregated data on adverse events and clinical failure rate do not show a major advantage for any of these antibiotics. It is striking that the adverse event rate reported for ticarcillin/clavulanic acid is low when compared to all other antibiotics, which is in contrast to severe adverse events reported for clavulanic acid. The data of quinolone studies in intra-abdominal infections do not yet allow a recommendation, even when it is acknowledged that two studies were performed with good results and a good study plan. In conclusion, the comparability of antibiotic studies in intra-abdominal infections is limited due to a lack of disease severity stratification and a relatively small study population for most antibiotics. The clinical success rate of the best-studied antibiotics is similar and the choice which antibiotic is used depends on the expected pathogens and the resistance rate in a clinical setting.