Drug Resistance of Enteric Bacteria Ii

Abstract

Transmissible drug-resistance (R) factors, which transfer resistance to tetracycline (TC), chloramphenicol, streptomycin, and sulfonamide by cell-to-cell contact, were found to be transduced in the system of Salmonella E group with phage epsilon (e15 and E34). The R+ transductants of S. newington (S-84) and S. chittagong (S-224) were all found to be unable to transfer their R factors by conjugation, and their R factors were not eliminated by treatment with acridine dyes so far as tested. The R factors containing TC resistance were consistently segregated when transduced. At low multiplicities of infection, the R+ transductants with E,5 were all nonlysogenic and unable to produce normal E15 phage particles; among the R+ transductants with E34, 34 % were lysogenic and 66% were sensitive to E34 It was found that multiple drug resistance was transferred in vitro from resistant Escherichia coli to shigellae, and also from resistant shigellae to E. coli (Ochiai et al., 1959; Akiba et al., 1960). We confirmed this finding and demonstrated that this transmission is not mediated by transduction, transformation, or a filtrable agent, but by cell-to-cell contact (Mitsuhashi, Harada, and Hashimoto, 1960; Harada et al., 1961). This was also confirmed by blender treatment (Watanabe and Fukasawa, 1960a, b).

Formation of Recombinants Between Nontransmissible Drug-Resistance Determinants and Transfer Factors

“…It was reported previously that nontransferable drug-resistance determinants, obtained by transduction of R factors with phages e or P1 (1,6), acquired the ability to transfer by conjugation after recombination with the sex factor, F, or wild-type R factors (2-4, 7, 8). Since known sex factors apparently can recombine with nontransferable R-factor derivatives to form functional, infectious R factors, it was of interest to study the distribution of genetic elements (termed T factors) among clinical isolates capable of conferring conjugal ability on noninfectious drug-resistance determinants.…”