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

INTRODUCTION: 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.