Improved method for obtaining streptomycin-dependent mutants from Pasteurella multocida and Pasteurella haemolytica, using N-methyl-N'-nitro-N-nitrosoguanidine.

N-Methyl-N'-nitro-N-nitrosoguanidine was used in a modified and improved procedure to obtain streptomycin-dependent mutants of type A Pasteurella multocida and type 1 Pasteurella haemolytica. The relative virulence of these mutants was determined by mouse inoculation with and without streptomycin.