None of the above-selective gut decontamination involves the use of orally administered antibiotics that achieve a high intraluminal level directed against gram-negative aerobes and yeast, leaving the host anaerobic intestinal microflora relatively undisrupted. although a reduction and alteration of the microorganisms responsible for infectious episodes have been demonstrated in certain groups of patients, a clear-cut impact on host mortality has not been shown. because lps may be responsible for toxicity both directly and through host mediator systems, the availability of agents to bind against this portion of the gram-negative bacteria to reduce mortality has been intensively examined. unfortunately, large multicenter randomized trials provide no evidence of benefit for this treatment. similarly, since many of the systemic manifestations of gram-negative bacteremia are mediated by cytokines, the effect of an anti-tnf antibody preparation is currently in clinical trial. no proven benefits have yet been identified. finally, the use of immunostimulants to enhance the state of activation of host defenses has been proposed. thymopentin is a peptide that contains active thymopoetin, a thymic molecule that acts to stimulate t-lymphocyte activity. preliminary trials indicate that this agent ameliorates host septic response after major operations and trauma but conclusive evidence that concurrent reduction of infection-related mortality occurs is not available.