In vitro assessment of sulbactam plus cefoperazone in the treatment of bacteria isolated from cancer patients.

Cefoperazone is a broad-spectrum cephalosporin that has been used extensively to treat infections in cancer patients. A recent survey demonstrated only a 6% resistance to this drug among Gram-negative bacteria. The combination of cefoperazone plus sulbactam was studied in vitro against consecutive isolates causing bacteremia in cancer patients as well as those selected for resistance to cefoperazone. Both a fixed ratio of sulbactam/cefoperazone (2:1 w/w) and selected concentrations of sulbactam (2, 4, 8, and 16 micrograms/ml) were studied. Sulbactam was shown to increase the susceptibility of various unselected Gram-negative bacilli; this effect increased with larger concentrations of sulbactam. The addition of sulbactam at optimum concentration levels made 29 of 65 cefoperazone-resistant Gram-negative bacilli susceptible. This effect was seen most markedly for Acinetobacter spp.