Demonstration of R Factors in Strains of Escherichia coli Isolated from Domestic Animals

Some Escherichia coli strains were isolated from 62 cattle, 4 sheep, and 14 goats, and surveyed for drug-resistance and distribution of R factors. Of the 62 cattle examined, 21 animals (34%) harbored drug-resistant E. coli strains, in which the resistance was transferable by conjugation. Drug-resistant E. coli strains were isolated neither from sheep nor from goats so far as examined. Of the drug-resistant strains, (TC, SM, SA)-resistant strains were isolated most frequently, and followed by (SM, SA)-resistant strains.In contrast, the isolation frequency of (TC, SM)-, (TC, SA)-, TC-, SM-and SA-resistant strains was less than 10%.Of 21 cattle carrying resistant E. coli strains, 9 animals (43%) excreted E. coli strains harboring R factors.A survey on drug-resistance patterns of R factors disclosed that (TC, SM, SA)-resistant R factors were isolated most frequently, and followed by (SM, SA)-, (TC, SA)-, TC- and SM-resistant R factors in a decreasing order.