Effect of 5-fluorouracil, mitoxantrone, methotrexate, and vincristine on the antibacterial activity of ceftriaxone, ceftazidime, cefotiam, piperacillin, and netilmicin.

Using the checkerboard agar dilution technique, antibacterial activity and in vitro interactions of 4 antineoplastic agents and 5 antimicrobial drugs were examined against 56 strains of 7 bacterial species. 5-fluorouracil was found to inhibit all strains of Staphylococcus aureus and of Staphylococcus epidermidis at a concentration of 0.8 micrograms/ml or less. 84% of all gram-negative strains were inhibited synergistically when 5-fluorouracil was combined with beta-lactam antibiotics. Methotrexate and cefotiam were antagonistic in 42% of all combinations, especially when tested against Escherichia coli and Klebsiella pneumoniae.