Chemical and Biological Studies on 1,2-Dihydro-s-Triazines. VI. Development of Resistance by Streptococcus faecalis No. 8043

Summary

A number of strains have been isolated from stock cultures of S. faecalis No. 8043 which are resistant to inhibition by the 1,2-dihydro-s-triazines in pteroylglutamic acid assay systems. The strains studied so far exhibit cross-resistance with related aldehyde and ketone derivatives of the dihydrotriazine series but not with 4-aminopteroylglutamic acid, 4-amino-N¹⁰-methylpteroylglutamic acid or certain 2,4-diaminopyrimidines.

The results of variance analyses were compatible with the conclusion that dihydrotriazine resistance originates from spontaneous mutations independently of the inhibitor. However, the possibility that resistance to minimal concentrations of inhibitor may be an adaptive change could not be excluded.