[Transmissible drug resistance in strains of E. coli isolated from birds]

A total of 97 strains of Escherichia coli, resistant either to one or to several theraupeutic agents and isolated from young and adult birds, were studied for the presence of transmissible R plasmids. Transmissible drug resistance was demonstrated with 37 per cent of the strains. The transmission of such resistance was manifested in highest percent in the case of ampicillin and chloramphenicol, followed by sulphathiazole and tetracycline. The R plasmids established in multi-drug resistant strains with three markers and more, were found to bear high percent determinants of resistance to chloramphenicol and in lower percent such to sulphathiazole and tetracycline. The same strains presented R plasmids that bore determinants of resistance to five therapeutic agents (Tc, Su, Cm, Mm, Nm) and to three therapeutic agents (Cm, Ap, Tc) and (Cm, Su, Km).