Dale E. Hunt

Cytosine Arabinoside Sensitivity in Actinobolin-Resistant Streptococcus faecalis The Basis of a Utilitarian Microbiological Assay.

Summary The observation that cytosine arabinoside was inhibitory for a strain of Streptococcus faecalis resistant to the antibiotic actinobolin served as the basis for the development of a microbiological assay for cytosine arabinoside in biological materials. Small volumes of less than one ml are sufficient for the assay and as little as 3 μg of cytosine arabinoside/ml of sample can be measured. The biological utility of this assay has been demonstrated.

Methyl 5 (or 4)-(3,3-dimethyl-1-triazeno)imidazole-4 (or 5)-carboxylate (NSC 87982): mouse tissue concentrations as determined by microbiological assay.

Summary Using a strain of Escherichia coli ATCC 9637 resistant to 8-azaguanine, a microbiological assay has been developed for a new broad spectrum antimicrobial compound, methyl 5 (or 4)-(3,3-dimethyl-1-triazeno)-imidazole-4(or 5)-carboxylate (NSC 87982). As little as 0.75 μg of NSC 87982/ml of sample can be detected. The applicability of this assay has been demonstrated for the estimation of concentrations of this drug in various tissues of mice.

Inhibition of Nucleic Acid and Protein Synthesis in Escherichia coli by a New Triazenoimidazole.

Methyl S (or 4) - (3,3 - dimethyl −1 - triazeno) imidazole-4 (or 5)-carboxylate(1), designated NSC 87982 by the Cancer Chemotherapy National Service Center, National Cancer Institute, National Institutes of Health, has been reported to be a potent inhibitor of Gram-positive and Gram-negative bacteria, yeasts, filamentous fungi and algae in vitro and to protect mice against an experimental infection of Staphylococcus aureus (2). Microbiological assay of various mouse tissues indicates that not only are significantly high blood levels obtained following oral, intraperitoneal, or intravenous administration of the drug, but also that detectable concentrations of NSC 87982 are found in the brain and other organs of the mice(3). The broad-spectrum antimicrobial activity of NSC 87982 and the knowledge that it is being considered for clinical trial prompted a study of the mechanism of action of this compound. Materials and methods. The inhibitory activity of NSC 87982 against numerous strains of Escherichia coli and Streptococcus faecalis which are resistant to various antimicrobial agents or radiation(4) was determined using previously described procedures (5); the spread-plate procedure(6) was used to determine the effect of metabolites (amino acids, B vitamins, purines, pyrimidines) on inhibition of E. coli by NSC 87982-details of this technique have been reported (7,8). Protein determinations were made by the method of Lowry et al (9). Ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) were determined by procedures previously described (10,11). By serial transfer in a simple glucose-salts medium containing increasing concentrations of NSC 87982, a culture of E. coli ATCC 9637 was obtained, (designated E. coli/NSC 87982) which is 30-foldresistant to the inhibitor. Results and discussion. Strains of E. coli or S. faecalis resistant to various antibiotics, antimetabolites, or irradiation were not cross-resistant to NSC 87982.