A sulfanilamide resistant strain Ts-5 of Pseudomonas mallei was isolated in the experiments on sulfazine therapy of malleus. The spectrum and level of the strain cross resistance to sulfanilamides and trimethoprim were studied. The frequency of the SurTrr mutants of P. mallei was determined. Efficient antibacterial drugs for the therapy of malleus caused by the sulfanilamide resistant strain are recommended.