Abstract
Eighty-eight (49%) of 179 drug-resistant Escherichia coli isolated from piggery waste carried conjugative R plasmids, of which 16 were thermo-sensitive, and so did 19 (27%) of 70 resistant strains from dairy farm waste, of which two were thermo-sensitive. Forty-nine conjugative R plasmids (37 from swine and 12 from bovine E. coli) were tested for incompatibility and fertility inhibition. Twenty-seven of them were classified into 11 incompatibility groups [Iα(7), H1(6), H2(3), FII(2), N(2), FIV(2), FI(1), B(1), K(1), P(1) and X(1)]. Those derived from swine samples were distributed in more different Inc groups (10 groups) than those from bovine samples (3 groups).
