[Antibiotic resistance and transferable antibiotic resistance of Escherichia coli isolated from Swedish calves 5 and 30 days old].

E. coli strains isolated from 5-day-old and 30-day-old healthy calves were tested for antibiotic resistance and H-factor mediated antibiotic resistance. An average of 1.6 antibiotic-resistant strains and 1.1 strains with transferable antibiotic resistance were isolated from each of the investigated calves. In comparison with the 30-day-old calves, the 5-day-old calves had significantly more strains with transferable antibiotic resistance (95.8 percent as against 63.4 percent). The R+ strains isolated from the younger calves transferred significantly more en bloc (43.5 percent as against 10.0 percent) and double plus multiple resistance (5292 percent as against 24.4 percent) than did those isolated from the older calves. The most common resistance was to sulphonamide and tetracycline and the most common transferred resistance was to sulphonamide.