A Factor in Agar which reverses the Antibacterial Activity of 1-Methyl-3-nitro-1-nitrosoguanidine

Abstract

WHILE working with 1-methyl-3-nitro-1-nitrosoguanidine, an anticancer agent in mice^1,2 and an antibacterial agent in vitro, we observed that Difco agar contained a factor which inhibited the activity of 1-methyl-3-nitro-1-nitrosoguanidine against Escherichia coli strain S. The activity of this compound was tested by the filter paper disk-assay method on minimal³ medium pH 6.8, containing 2 per cent agar. The zones of inhibition were smaller when the medium was sterilized by steaming for 20 min. than when sterilized by autoclaving (15 lb./sq. in.) for the same length of time (Table 1). Several lots of Difco agar had the same property, but other commercially available agars did not. These latters agars are : BBL (Baltimore Biological Laboratory), NBC (Nutritional Biochemical Co.), ‘Ion Agar No. 2’ (Oxo, Ltd., London), and Difco ‘Noble Agar’.