Combined Action of 6-Mercaptopurine and Antibiotics on Gram-Negative Bacteria in Vitro 1

Abstract

Summary

The antibacterial activity of a commonly used antimetabolite, 6-mercapto-purine (6-MP), was studied in vitro using chemically defined media. 6-Mercaptopurine (1-5 μg/ml) had weak bacteriostatic activity against Escherichia coli, klebsiella, enterobacter and pseudomonas. Synergism occurred between 6-MP and aminoglycoside antibiotics whereas 6-MP was weakly antagonistic to the action of penicillin and cephalosporin antibiotics. These combined actions were not reversed by fetal bovine serum (50%) but were readily reversed by an excess of hypoxanthine or adenine. No interactions occurred between 6-MP and tetracycline, chloramphenicol or polymyxin B.

The authors are indebted to Mrs. Susan Knorr for excellent technical assistance.