A transferable extended-spectrum produced by a multidrug-resistant clinical isolate of Gram-negative bacilli isolates from patients with diarrhoea was studied. The gene was carried by a large plasmid were transferable to recipient strains of Escherichia coli MM294. The transfer of gene determinant from donor strains was demonstrated by the analysis of resistance spectrum in transconjugat clones of recipient strain by the method of indirect selection. The ability of production of extended-spectrum beta-lactamase (ESBL) was demonstrated by the double disc diffusion test. It is concluded that pencillinase and the resistance markers for pencillin was encoded by 4.2 kb plasmid, while that cephalosporinase and the resistance markers for cefotaxime and cephaloxin were encoded by 3.2 kb plasmid transferred by conjugation into Escherichia coli MM294.