Synergistic combinations of antibiotics in gram-negative bacillary infections.

In vitro synergy (or at least an additive effect between antibiotics in vitro) is likely to have clinical significance. Data in the literature strongly suggest that, in patients who lack the natural mechanisms of defense against infection, better clinical results can be achieved by treatment with two drugs to which the pathogenic organism is sensitive rather than only one. Moreover, there is some evidence that the use of antibiotic combinations found to be synergistic in vitro is associated with a better clinical outcome in patients with decreased mechanisms of defense against infection, especially neutropenia. The use of synergistic drug combinations should be continued as empirical therapy in severely neutropenic or otherwise compromised patients, especially in those with malignant tumors.