The selection of trimethoprim resistant Escherichia coli in the faecal flora of piglets sucking a sow treated parenterally with trimethoprim

Abstract

The parenteral administration of a therapeutic preparation containing trimethoprim to a lactating sow was associated with the appearance of trimethoprim resistant Escherichia coli in the faeces of the sow and her piglets. The E. coli isolates were differentiated into strains on the basis of their O‐serogroup, biotype and resistance pattern. The majority (75%) of trimethoprim resistant strains were isolated only from the faeces of the piglets during the 14 d survey period. This suggested that the agent must have been excreted at a sufficiently high concentration in the milk to select for resistant strains present in the minority flora of the sucking pigs.