Identification of Nitrosodimethylamine-forming Anaerobic Bacteria Isolated from the Stomach Contents of the Monkey (Macaca irus)

In Vitro culture of 49 strains of anaerobic bacteria isolated from the stomach of monkeys was carried out to identify those with the ability to form nitrosodimethylamine (NDMA) in GAM broth containing sodium nitrite (1000ppm) and dimethylamine (500ppm). The medium was adjusted to pH 6.The results were as follows:1) Of the 49 strains of anaerobic bacteria, including the family Bacteroidaceae (dominant strains in the stomach), the following 18 strains were recognized as NDMA-forming bacteria: Bacteroides coagulans (2 strains), B. melaninogenieus ss. melaninogenicus (2 strains), B. corrodens (1 strain), Fusobacterium nucleatum (5 strains), Bacteroidaceae spp. (5 strains), Eubacterium lentum (2 strains), and Peptostreptococcus sp. (1 strain).2) Comparative studies of the rate of NDMA formation and the pH dependence indicated that the rate of NDMA formation by the anaerobic NDMA-forming bacteria was (1.1 to 1.5 times) higher than that in the blank culture and the pH was unchanged, while the aerobic strains, except for Neisseria sicca and Streptococcus equi showed a rate two to three times higher than that of the blank culture and the pH apparently decreased to a final pH of about 5.5 (5.1 to 5.9).3) Studies on NDMA formation in GAM broth with 0.3% glucose or in brain heart infusion with 0.2% glucose showed that anaerobic NDMA-forming strains were non-glucose fermenters, whereas aerobic ones were glucose fermenters and oxidizers. It was concluded that there was no specific relationship between NDMA formation and the utilization of glucose.