Transferable Drug Resistance inPseudomonas aeruginosa

Abstract

Three strains ofPseudomonas aeruginosawere demonstrated to transfer double-drug resistance by conjugation to aP. aeruginosarecipient at frequencies of 10−4to 10−2per recipient cell. Two of the three strains also transferred toEscherichia coliat frequencies which were 103- to 105-fold lower, but the third strain could not be demonstrated to do so. The latter strain, however, conferred maleness on thePseudomonasrecipient. The transfer of streptomycin resistance was associated with the acquisition of streptomycin phosphorylase by bothP. aeruginosaandE. colirecipients. Maximal broth mating frequencies were obtained with nonagitated cultures less than 1 mm in depth. A pyocine selection system based on donor sensitivity and recipient resistance is described and appears to have future value as a generalized selective device for use after matings.