Occurrence of quinolone-resistant Escherichia coli in environmental samples from a sow pool system in Switzerland

Fluoroquinolones (FQ) undergo minimal metabolization in animals and are excreted via faeces and urine, where they enter the environment almost unchanged. In this study we investigated the presence of quinolone-resistant Escherichia coli (E. coli) in the environment of 65 farms of a sow pool system in Switzerland. Two hundred and seventy-nine samples from liquid manure and wipes of dust and pen walls were collected and the use of FQ on the farms was investigated. From 45% of dust samples, 52% of pen wall samples and 69% of liquid manure samples quinolone-resistant E. coli (QRE) were cultivated. Significant higher counts of quinolone-resistant colonies were found in liquid manure samples than in dust (p < 0.01) or pen wall samples (p < 0.05). Samples from breeding farms were significantly more often positive than samples from fattening farms (p < 0.01). Samples taken from farms using FQ were significantly more frequently positive for QRE than samples from farms without FQ usage (p < 0.01). On 97% of the farms with FQ use and 85% (23/27) of the farms without FQ use QRE could be found in at least one sample (no significant difference). Overall, QRE were widespread in the environment of the investigated pig farms.