The antibiotics Exceed and Excenel are two formulations of the cephalosporin drug, ceftiofur. They are commonly used to treat finishing pigs in the United States.

Dr Wittum explained that the objective of this work at Ohio State University was to understand the relationship between the use of ceftiofur and the spread of important cephalosporin-resistant genes in swine finishing barns.

To do this, they collected about 30 faecal samples from each of 50 finishing barns located in five states and then tested them for the presence of E. coli or Salmonella that were resistant to ceftiofur and other important antibiotics.

Any isolates resistant to ceftiofur were then tested for specific genes that provide resistance to important cephalosporins.

Of the faecal samples tested, 109 (7.3 per cent) were positive for Salmonella but only two were resistant to ceftiofur.

A total of 78.5 per cent of the faecal samples contained E. coli but only 1.6 per cent contained E. coli or other bacteria with the resistant gene.

This result suggests that the spread of resistant bacteria in swine finishing barns cannot be fully explained by simply measuring antibiotic use, concluded Dr Wittum.

In his report for Pork Checkoff, he concluded that attempts to reduce resistance will likely require that complex relationships of factors be identified that promote the spread of resistant organisms and resistance genes.

November 2014